DESCRIPTION
TITLE OF THE INVENTION
STATE DETECTING METHOD, CORRECTION VALUE PROCESSING
5 DEVICE, POSITIONING SYSTEM, AND STATE DETECTION PROGRAM
TECHNICAL FIELD
[000 1]
The present invention relates to a state detecting method, a
10 correction value processing device, a positioning system, and a state
detection program and, more particularly, relates to a method of detecting
an abnormal state of a base station in a differential GPS having a plurality
of base stations.
15 BACKGROUND ART
[0002]
In recent years, scenes of performing positioning by usmg a GPS
(Global Positioning System) are increasing, and dependence on a GPS in
daily life is increasing.
20 [0003]
A delay may occur in propagation by the influence of the
ionosphere and aerosphere in which radio waves carrying signals propagate
such as a case of receiving a signal from a GPS satellite from a low
elevation angle, and there is a limit on precision of positioning using a
25 GPS.
[0004]
A differential GPS whose precisiOn of positioning by a GPS IS
improved by installing a base station fixed to the surface of the earth m
order to solve the problem is being spread.
30 [0005]
2
However, the positioning precision of a differential GPS depends
on the precision of the time and position of a base station. For example,
when abnormality occurs in the operation of a base station, it affects a
correction signal. A GPS user receiver which receives the correction
5 signal, corrects a signal received from a GPS satellite, and performs
positioning estimates a position different from a correct position as the
position of itself.
[0006]
The influence of an error in positioning by a GPS to the daily life is
10 enormous. Consequently, the differential GPS is requested to detect a
failure in the operation of a base station early and avoid influence on the
correction value.
[0007]
A requirement determined for a base station of a differential GPS
15 currently operated as the GBAS (Ground Based Augmentation System)
standard is that an integrity risk is 1 o-s per 150 seconds. The integrity
risk denotes integrity loss probability. The requirement is determined by
the ICAO (International Civil Aviation Organization)/RTCA (Radio
Technical Commission for Aeronautics). The probability that two base
20 stations satisfying the requirement fail at the same time is about 1 o-IO. In
operation of the GBAS, this numerical value may be ignored in the
category I (CAT-I) in which the integrity risk as a requirement is 1 o-7 but is
unignorable in the categories II and III (CAT-II/III) in which the integrity
risk is 1 o-9
.
25 [0008]
PTL 1 discloses a method of detecting a base station in which
abnormality occurs in a differential GPS (DGPS) using a plurality of base
stations. When N pieces of GPS satellites and K pieces of base stations
are specified by being designated with indexes "n" and "k", a
3
receiver/satellite specific differential adjusted value adjusted so that clock
bias is removed and common measurement time is reflected is set as C",k.
The receiver/satellite specific differential adjusted value is generated by
differential adjustment processing means on the basis of a GPS signal
5 received from a GPS satellite. First, on the basis of the received GPS
signal and the known measurement position of a GPS signal receiver of a
base station fixed to the surface of the earth, a satellite specific differential
adjusted value is generated. The GPS signal receiver has a clock time
offset or bias from the atomic clock time of the GPS satellite, and
10 receiver/satellite specific measurement values have different measurement
times. The GPS signal receiver generates a differential adjusted value
accompanymg no clock bias from the receiver/satellite specific
measurement values. Then, the GPS signal receiver adjusts the
receiver/satellite specific adjusted values in accordance with common
15 synchronization time. By the processes, the receiver/satellite specific
differential adjusted value cn,k adjusted so that the clock bias is eliminated
and common measurement time is reflected is obtained.
[0009]
It IS now assumed that a satellite specific differential adjusted
20 average value is a value obtained by performing arithmetic averaging
on the receiver/satellite specific differential adjusted values cn,k adjusted
so that the clock bias is eliminated and common measurement time is
reflected among the base stations.
differential correction average value
25 relational equation.
= (1/K)(Cn,I + cn,2 + ... + C",K)
That is, the satellite specific
is obtained by the following
As an amount used for a test, receiver-satellite-specific
discriminant value zn,k IS used. It IS assumed that the
receiver-satellite-specific discriminant value zn,k is the difference between
4
the receiver/satellite specific differential adjusted value cn,k and the
satellite specific differential correction average value . That is, it is
obtained by the following relational equation.
zn,k = cn,k _
5 At this time, by a predetermined detection threshold DTn,k, determination
of a base station is performed. That is, a base station is determined by
the following determination equation.
IZn,kl > DTn,k
Concretely, in the case where the determination equation IZn,kl > DTn,k is
10 satisfied in all of GPS satellites (n = 1, ... , N) to a given base station k, it is
determined that the base station k has abnormality.
15
20
25
[00 1 0]
PTLs 2 to 5 also disclose related arts.
Citation List
[0011]
PTL 1: US Patent Publication 5,600,329
PTL 2: Japanese Unexamined
2003-057327
PTL 3: Japanese Unexamined
2007-010422
PTL 4: Japanese Unexamined
2009-168804
PTL 5: Japanese Unexamined
2011-043449
Summary of Invention
Technical Problem
[0012]
Patent
Patent
Patent
Patent
Application
Application
Application
Application
Publication No.
Publication No.
Publication No.
Publication No.
5
In the PTL 1, a base station in which abnormality occurs can be
detected but there is a problem as described below. A test by the
determination expressiOn IS performed only m the range domain
(measurement of the distance from a GPS user receiver (such as an aircraft)
5 to a GPS satellite). Therefore, in the case where the absolute value of the
receiver-satellite-specific discriminant value is less than the threshold, it
is not regarded that abnormality occurs. However, when the sign of the
receiver-satellite-specific discriminant value is deviated to the negative
side or the positive side, it is feared that a critical position error occurs in
10 a position domain (determination of the position of the GPS user receiver).
In addition, in calculation of the average value among base stations, a
correction value from a base station in which abnormality occurs is also
included, and it cannot be said that the determination of presence/absence
of abnormality is accurately reflected in the receiver-satellite-specific
15 discriminant value used for the test. For example, for an abnormal base
station, the receiver-satellite-specific discriminant value becomes small,
and there is the possibility that a detection failure occurs. For a base
station which is not abnormal, the receiver-satellite-specific discriminant
value increases, and erroneous detection may occur.
20
Solution to Problem
[0013]
To achieve the object, a state detecting method of the present
invention is a state detecting method of detecting an abnormal state of a
25 base station in a positioning system having a satellite and a base station
and includes the steps of: obtaining a first positioning position of the base
station on the basis of a signal received from the satellite by the base
station; selecting predetermined number of master base stations in
ascending order of a distance between preliminarily given position
6
information of the base station and the first positioning position of the
base station; generating a correction value of the master base station on the
basis of a signal received from the satellite by the master base station;
obtaining a second positioning position of a base station other than the
5 master base station by correcting the first positioning position of the base
station other than the master base station with the correction value of the
master base station by the base station other than the master base station;
and determining that the base station other than the master base station is
in an abnormal state when the distance between a position by preliminarily
10 given position information of the base station other than the master base
station and the second positioning position is larger than a first threshold.
[0014]
A state detecting method of the present invention is a state
detecting method of detecting an abnormal state of a plurality of base
15 stations in a positioning system having a satellite and the plurality of base
stations and includes the steps of: obtaining a first positioning position of
the base station on the basis of a signal received from the satellite by the
base station; selecting, as a master base station, a base station whose
distance between preliminarily given position information of the base
20 station and the first positioning position of the base station lies m a
predetermined range; generating a correction value of the master base
station on the basis of a signal received from the satellite by the master
base station; obtaining a second positioning position of a base station other
than the master base station by correcting the first positioning position of
25 the base station other than the master base station with the correction value
of the master base station by the base station other than the master base
station; and determining that the base station other than the master base
station is in an abnormal state when the distance between a position by
preliminarily given position information of the base station other than the
7
master base station and the second positioning position 1s larger than a
first threshold.
[00 15]
A correction value processmg device of the present invention
5 includes: data receiving means receiving a signal received from a satellite
by a base station; first positioning position calculating means calculating a
first positioning position of the base station on the basis of the signal
received by the data receiving means; master base station selecting means
selecting predetermined number of master base stations in ascending order
10 of a distance between preliminarily given position information of the base
station and the first positioning position of the base station; master base
station correction value calculating means generating a correction value of
the master base station on the basis of a signal received from the satellite
by the master base station; second positioning position calculating means
15 calculating a second positioning position of a base station other than the
master base station by correcting the first positioning position of the base
station other than the master base station with the correction value of the
master base station by the base station other than the master base station;
and abnormality determining means determining that the base station other
20 than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
position is larger than a first threshold.
[00 16]
25 A correction value processmg device of the present invention
includes: data receiving means receiving a signal received from a satellite
by a base station; first positioning position calculating means calculating a
first positioning position of the base station on the basis of the signal
received by the data receiving means; master base station selecting means
8
selecting, as a master base station, a base station whose distance between
preliminarily given position information of the ba,se station and the first
positioning position of the base station lies in a predetermined range;
master base station correction value calculating means generating a
5 correction value of the master base station on the basis of a signal received
from the satellite by the master base station; second positioning position
calculating means calculating a second positioning position of a base
station other than the master base station by correcting the first positioning
position of the base station other than the master base station with the
10 correction value of the master base station by the base station other than
the master base station; and abnormality determining means determining
that the base station other than the master base station is in an abnormal
state when the distance between a position by preliminarily given position
information of the base station other than the master base station and the
15 second positioning position is larger than a first threshold.
[00 1 7]
A positioning system of the present invention is a positioning
system having a satellite, a base station, and a correction value processing
device, wherein the correction value processing device includes: first
20 positioning position calculating means calculating a first positioning
position of the base station on the basis of the signal received by the data
receiving means; master base station selecting means selecting
predetermined number of master base stations in ascending order of a
distance between preliminarily given position information of the base
25 station and the first positioning position of the base station; master base
station correction value calculating means generating a correction value of
the master base station on the basis of a signal received from the satellite
by the master base station; second positioning position calculating means
calculating a second positioning position of a base station other than the
9
master base station by correcting the first positioning position of the base
station other than the master base station with the correction value of the
master base station by the base station other than the master base station;
and abnormality determining means determining that the base station other
5 than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
position is larger than a first threshold.
10
[00 18]
A positioning system of the present invention is a positioning
system having a satellite, a base station, and a correction value processing
device, wherein the correction value processing device includes: first
positioning position calculating means calculating a first positioning
position of the base station on the basis of the signal received by the data
15 receiving means; master base station selecting means selecting, as a master
base station, a base station whose distance between preliminarily given
position information of the base station and the first positioning position
of the base station lies in a predetermined range; master base station
correction value calculating means generating a correction value of the
20 master base station on the basis of a signal received from the satellite by
the master base station; second positioning position calculating means
calculating a second positioning position of a base station other than the
master base station by correcting the first positioning position of the base
station other than the master base station with the correction value of the
25 master base station by the base station other than the master base station;
and abnormality determining means determining that the base station other
than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
10
position is larger than a first threshold.
[00 19]
A storage medium of the present invention is a storage medium
storing a program for detecting an abnormal state of a base station in a
5 positioning system having a satellite and the base station, including: a
process of calculating a first positioning position of the base station on the
basis of the signal received by the data receiving means; a process of
selecting predetermined number of master base stations in ascending order
of a distance between preliminarily given: position information of the base
10 station and the first positioning position of the base station; a process of
generating a correction value of the master base station on the basis of a
signal received from the satellite by the master base station; a second
positioning position calculating process of calculating a second
positioning position of a base station other than the master base station by
15 correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
the base station other than the master base station; and a process of
determining that the base station other than the master base station is in an
abnormal state when the distance between a position by preliminarily given
20 position information of the base station other than the master base station
and the second positioning position is larger than a first threshold.
[0020]
A storage medium of the present invention is a storage medium
storing a program for detecting an abnormal state of a base station in a
25 positioning system having a satellite and the base station, including: a
process of calculating a first positioning position of the base station on the
basis of the signal received by the data receiving means; a process of
selecting, as a master base station, a base station whose distance between
preliminarily given position information of the base station and the first
11
positioning position of the base station lies in a predetermined range; a
process of generating a correction value of the master base station on the
basis of a signal received from the satellite by the master base station; a
second positioning position calculating process of calculating a second
5 positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
the base station other than the master base station; and a process of
determining that the base station other than the master base station is in an
10 abnormal state when the distance between a position by preliminarily given
position information of the base station other than the master base station
and the second positioning position is larger than a first threshold.
Advantageous Effects of Invention
15 [0021]
According to the present invention, an abnormal state of a base
station in a satellite positioning system can be detected with high
precisiOn.
20 Brief Description of Drawings
[0022]
25
Fig. 1 is a diagram illustrating an example of the configuration of a
differential GPS according to a first exemplary embodiment of the present
invention;
Fig. 2 IS a flowchart illustrating an example of the procedure of a
method of detecting a state of a base station in the differential GPS
according to the first exemplary embodiment of the invention;
Fig. 3 is a diagram illustrating an example of the configuration of a
correction value processing dev·ice according to the first exemplary
12
embodiment of the invention;
Fig. 4 is a diagram illustrating an example of the configuration of a
data processing unit according to a second exemplary embodiment of the
present invention;
5 Fig. 5 is a flowchart illustrating an example of the procedure of a
method of detecting a state of a base station in the differential GPS
according to the second exemplary embodiment of the invention; and
Fig. 6 is a flowchart illustrating an example of the procedure of a
method of detecting a state of a base station in a differential GPS
10 according to a third exemplary embodiment of the present invention.
Description of Embodiments
[0023]
Best modes for carrying out the invention will be described
15 specifically with reference to the drawings. The present invention,
however, is not limited to the following exemplary embodiments.
[0024]
First Exemplary Embodiment
Fig. 1 illustrates an example of the configuration of a differential
20 GPS 101 according to a first exemplary embodiment of the present
invention.
[0025]
A receiving device 601 receives GPS signals from GPS satellites
201 to 20n and estimates the position of itself. The receiving device 601
25 is mounted in, for example, an aircraft.
[0026]
A plurality of base stations 301 to 304 receive GPS signals from the
GPS satellites 201 to 20n and transmit observation data to a correction
value processing device 401. The correction value processing device 401
13
receives the GPS signals from the GPS satellites 201 to 20n, calculates a
correction value at the time of measuring the position, and transmits the
correction value to a broadcast transmitting device 501.
[0027]
5 The broadcast transmitting device is, for example, a VDB (VHF
(Very High Frequency) Data Broadcast) transmitting device.
[0028]
The receiving device 601 receives a correction value broadcast
transmitted from the broadcast transmitting device 501, corrects the GPS
10 signals received from the GPS satellites 201 to 20n, and estimates the
position of itself.
[0029]
Fig. 3 illustrates an example of the configuration of the correction
value processing device 401 according to the exemplary embodiment.
15 The correction value processing device 401 has a data receiving unit 402
receiving observation data transmitted from the base stations 3 01 to 3 04,
and a correction value transmitting unit 405 transmitting correction value
information to the broadcast transmitting device 501 to provide it to the
receiving device 601. The correction value processing device further has
20 a data processing unit 403 processing the observation data received by the
data receiving unit 402 to generate correction value information, and a data
holding unit 404 holding data on the base stations 301 to 304. The data
holding unit 404 also temporarily holds the information processed by the
data processing unit 403 and holds values of parameters necessary for a
25 testing process to be described below.
[003 0]
Next, the procedure of a method of detecting the state of a base
station m the differential GPS according to the first exemplary
embodiment of the present invention will be described with reference to
Figs. 1 to 3.
[0031]
14
Although the number of base stations is four in the exemplary
embodiment, the invention is not limited to the number. The number of
5 base stations may be smaller than four or larger than four.
[0032]
The correction value processmg device 401 receives observation
data from the base stations 301 to 304 which received the GPS signals
generated from the GPS satellites 201 to 20n (step S201 in Fig. 2).
10 [0033]
Next, the correction value processmg device 401 measures the
position of each of the base stations 3 01 to 3 04 on the basis of the
observation data (point positioning) (step S202).
[0034]
15 The point positioning is executed by using pseudo ranges from the
four GPS satellites (distances from the GPS satellites to the receiver).
The precision of the clock provided in the receiving device 601 is inferior
to that of the atomic clock of the GPS satellite by a few digits. Even
when the transmission time of the radio wave of the atomic clock in the
20 GPS satellite is accurate, there is the possibility that a large error is
included in reach time measured by the receiver. To determine four
unknown amounts which are three-dimensional positions of receiving the
radio wave from the GPS satellite and, in addition, the error of the clock of
the receiving device 601, the pseudo ranges from the four or more GPS
25 satellites are used at the same time.
[0035]
The positioning position of a base station IS obtained by the point
positioning. To prevent variations in the precision of positioning among
the base stations, at least one of the following conditions may be set.
15
[003 6]
(1) A satellite of a low elevation angle (for example, 10 degrees or
less) is eliminated from positioning calculation to reduce a positioning
error due to the influence of ionosphere and aerosphere or multipath.
5 [003 7]
(2) Only common satellites which are visible from all of the base
stations are used for positioning calculation.
[003 8]
(3) Positioning calculation Is performed by usmg the same
10 clock/ephemeris (time/orbit) parameters to a given satellite. That is,
clock/ephemeris parameters to be used are made the same to GPS signals
transmitted from satellites.
[003 9]
Next, the correction value processmg device 401 selects a master
15 base station and a base station to be tested from the base stations 301 to
304 (step S203).
[0040]
Three-dimensional coordinate values are preliminarily given as
numerical values of high precision to each of the positions of the base
20 stations fixed to the surface of the earth. Hereinbelow, the position will
be called a measured position. The coordinate values on the measured
position are held in the data holding unit 404 in the correction value
processing device 401.
[0041]
25 The difference between the positioning position and the measured
position will be called a positioning error in the following. The
positioning error IS defined as a three-dimensional range. Those
arithmetic operations are performed by the correction value processing
device 401.
16
[0042]
On each of the base stations, the positioning position obtained by
the point positioning and the measured position are compared, and a base
station having the smallest positioning error and a base station having the
5 second smallest positioning error are selected. The base station having
the smallest positioning error is set as a master base station A, and the base
station having the second smallest positioning error is set as a master base
station B.
10
[0043]
Although two master base stations are selected m the exemplary
embodiment, when the number of master base stations is large, three or
more master base stations may be used.
[0044]
A base station which is not selected as a master base station
15 becomes a base station to be tested. In the exemplary embodiment, two
base stations remain, so that they become base stations X and Y to be
tested.
[0045]
Next, on the basis of the observation data obtained from the master
20 base stations and the values of the measured positions, the correction value
processing device 401 calculates DGPS correction values in the master
base stations (step S204 ). The DGPS correction value in the master base
station A is a DGPS correction value A, and the DGPS correction value in
the master base station B is a DGPS correction value B.
25 [0046]
The DGPS correction value is obtained as follows.
[004 7]
The pseudo range measured by a base station includes an error from
a true distance between the GPS satellite and the base station. The
17
pseudo range also includes an error caused by an internal no1se such as a
clock bias of the base station (the difference between time displayed by the
base station and true time) or a clock bias of the GPS satellite. Further,
the pseudo range includes a troposphere delay amount the base station
5 experiences, an ionosphere delay amount the base station experiences, a
multipath the base station experiences, and errors caused by internal noises
such as thermal noise the base station experiences.
[0048]
A pseudo range correction value is defined as a value obtained by
10 subtracting a pseudo range of a base station subjected to a smoothing
process from a geometric distance between a GPS satellite and the base
station, calculated from position information of the GPS satellite
broadcasted by the GPS satellite and a position obtained by measuring the
base station. The geometric distance between the GPS satellite and the
15 base station is obtained by adding an error of the position information of
the GPS satellite broadcasted by the GPS satellite and an error of a
distance obtained by measuring the base station to the true distance
between the GPS satellite and the base station.
[0049]
20 The pseudo range correction value derived from the relational
equation includes a clock bias of the satellite, a troposphere delay amount
the satellite experiences, an ionosphere delay amount the satellite
experiences, an error which is recognized as an error of the receiving
device and can be separated, and other errors.
25 [0050]
The pseudo range correction value by the base station obtained is
applied to correction of the pseudo range of the receiving device. The
pseudo range of the receiving device includes the true distance between the
GPS satellite and the receiving device, an error component which can be
5
18
separated In a process of positioning calculation as a clock bias of the
receiving device, and an error component evaluated by using a standard
deviation peculiar to each of observation amounts or assumed.
[0051]
Actual pseudo range correction values are averaged by a plurality
of base stations. By the operation, a random error by multipath
propagation, noise of the receiving device, and the like is suppressed. On
the other hand, the ionosphere delay amount and the troposphere delay
amount are averaged and remain.
10 [0052]
Subsequently, a test of selection of a master base station is executed
(step S205). The two master base stations performs DGPS positioning by
applying their DGPS correction values to each other, and the results of the
positioning are compared with their measured positions. Since selection
15 of the master base station depends on the point positioning as described
above, regardless of the presence of abnormality, there is the possibility
that the positioning error becomes small by chance. The test of the
selection of the master base station eliminates this possibility.
20
[0053]
When a base station operates normally, the positioning position
obtained by the result of the point positioning reproduces the measured
position of the base station with high precision. That is, in a base station
with a large positioning error, a failure in the operation is suspected. It is
feared that, by a correction value generated from a base station in which a
25 failure occurs, a GPS signal is corrected to a direction deviated from a
correct position. Inclusion of the correction value in the correction value
information to be provided to the receiving device 601 becomes a cause of
. .
Increase In an error.
[0054]
19
A selection of a base station as a master base station because a
positioning error is small in the point positioning by chance regardless of
the fact that abnormality occurs in the base station and a DGPS correction
value by the base station does not give a normal positioning result is not a
5 proper selection. When the selection of a master base station is not
proper as described above (NO in step S206), the correction value
processing device 401 corrects the selection of the master base station
(step S207) and calculates a correction value of a master base station
newly selected (step S204 ).
10 [005 5]
When the selection of a master base station is proper (YES in step
S206), the correction value processing device 401 applies the DGPS
correction value of the master base station to a base station to be tested and
performs a DGPS positioning (step S208).
15 [005 6]
Subsequently, a test on the base station to be tested IS executed
(step S209).
[0057]
The difference between the DGPS positioning result of the base
20 station to be tested and the positioning result of each of base stations is
obtained. When the value of the difference exceeds a predetermined
threshold with respect to the DGPS correction values of two master base
stations, it is determined that the base station to be tested IS abnormal.
Table 1 illustrates the logic of pass/fail determination.
25
[005 8]
Table 1 Pass/fail determination logic
20
Determination Determination Overall
by DGPS by DGPS determination
correction value correction value
of master base of master base
station A station B
Base station X to pass pass pass
be tested pass fail pass
fail pass pass
fail fail fail
Base station Y to pass pass pass
be tested pass fail pass
fail pass pass
fail fail fail
[0059]
A threshold used for the determination may be changed according to
precision of the positioning. For example, the threshold may be
determined on the basis of PDOP (Position Dilution of Precision) in which
5 a disposition state of a GPS satellite is reflected and the number of
satellites for the following reason. In some cases, the PDOP changes
according to increase/decrease of the number of satellites, and the
positioning precision changes. There is consequently the possibility that,
with a fixed threshold, the determination becomes inaccurate.
10 [0060]
In comparison between a DGPS positioning result and a measured
position, if the difference is disassembled into a vertical-direction
component and a horizontal-direction component, the magnitude of an
error cannot be accurately reflected. Therefore, evaluation is performed
15 on the basis of a distance in three dimensions. To a testing process based
on the three-dimensional distance, the Maxwell-Boltzmann distribution is
applied.
[0061]
21
In operation of the GBAS, to GPS signals from one GPS satellite,
DGPS correction values from a plurality of base stations are averaged for
5 the base stations. An obtained average value is supplied to a receiving
device. By averaging DGPS correction values from a plurality of base
stations operating normally and providing an average value to a receiving
device, variations in the base stations are suppressed, and the receiving
device can measure the position of itself with higher precision.
10 [0062]
The data processmg unit 403 m the correction value processmg
device 401 generates correction value information by excluding
observation data from a base station to be tested which was determined as
"fail" as a result of the test. The correction value transmitting unit 405
15 transmits the correction value information to the broadcast transmitting
device 501.
[0063]
Next, the process of data in the correction value processing device 401 will
be described specifically.
20 [0064]
First, the correction value processmg device 401 performs point
positioning on the base stations 301 to 304. As described above, a GPS
signal from a GPS satellite which may cause an error in positioning is
excluded. For the point positioning, GPS signals from n pieces of GPS
25 satellites 201 to 20n are used. Three-dimensional coordinate values of a
positioning position of a base station obtained by the point positioning are
described as follows.
[0065]
Base station 301: (Xsa!, Ysal, Zsal)
5
Base station 302: (Xsa2, Ysa2, Zsa2)
Base station 303: (Xsa3, Ysa3, Zsa3)
Base station 304: (Xsa4, Ysa4, Zsa4)
[0066]
22
The three-dimensional coordinate values of the measured positions
for the base stations 301 to 304 are described as follows.
[0067]
Base station 301: (xi, YI, zJ)
Base station 302: (x2, y2, z2)
10 Base station 303: (x3, y3, z3)
Base station 304: (x4, y4, Z4)
[0068]
From the coordinate values, the difference between the. point
positioning position and the measured position on each of the base stations
15 301 to 304 is obtained as a three-dimensional distance.
[0069]
Base station 301: L1sal = ~(XsaJ-XJ) 2 +(ysal-yJ) 2 +(zsai-ZI) 2 )
Base station 302: L1sa2 = ~(Xsa2-X2) 2 +(Ysa2-Y2) 2 +(zsa2-Z2) 2 )
Base station 303: L1sa3 = ~(Xsa3-X3) 2 +(Ysa3-Y3) 2 +(zsa3-Z3) 2 )
20 Base station 304: L1sa4 = ~(Xsa4-X4) 2 +(Ysa4-Y4) 2 +(zsa4-Z4) 2 )
[0070]
The small/large relations are examined on the differences obtained
by the above process. In the exemplary embodiment, it is assumed that,
for example, the following small/large relations are obtained.
25 [0071]
L1sa3 > L1sal > L1sa4 > L1sa2
That is, it is assumed that the difference between the point
positioning position and the measured position on the base station 3 03 is
the largest and the difference on the base station 3 02 is the smallest.
23
[0072]
On the basis of the small/large relations, the base station giving the
smallest difference and the base station giving the second smallest
difference become master base stations. Specifically, the base station 3 02
5 becomes the master base station A, and the base station 304 becomes the
master base station B. A base station giving a larger difference than
these base stations is set as a base station to be tested. In the exemplary
embodiment, the base station 3 03 becomes a base station X to be tested,
and the base station 301 becomes a base station Y to be tested.
10 [0073]
Subsequently, a DGPS correction value in the master base station is
obtained.
[0074]
On the basis of the GPS signals from the n pieces of GPS satellites
15 201 to 20n used for the point positioning, the DGPS correction values
obtained in the master base stations are described as follows.
[0075]
Positioning position by CA of base station X to be tested: (XctgpsXA, YctgpsXA,
ZctgpsXA)
20 Positioning position by CB of base station X to be tested: (XctgpsXB, YctgpsXB,
ZctgpsXB)
Positioning position by CA of base station Y to be tested: (XctgpsYA, YctgpsYA,
ZctgpsYA)
Positioning position by CB of base station Y to be tested: (XctgpsYB, y ctgpsYB,
25 ZctgpsYB)
[0076]
The obtained coordinate values are used for a test of a base station
described below.
[0077]
24
Similarly, the master base stations A and B apply their DGPS
correction values to each other and execute DGPS positioning to each other.
The obtained positioning positions are described as follows.
[0078]
5 Positioning position by C8 of master base station A: (XctgpsAB, y dgpsAB,
ZctgpsAB)
10
Positioning position by CA of master base station B: (XctgpsBA, YctgpsBA,
ZctgpsBA)
[0079]
The difference between the obtained positioning position and the
measured position is obtained as a three-dimensional distance.
On master base station A
i'1ctgpsA = -) ( (XctgpsAB-X2)2+(y dgpsAB-Y2) 2+(ZctgpsAB-Z2) 2)
On master base station B
15 i'1ctgps8 = -) ( (XctgpsBA -X4)2+(y dgpsBA -y 4 )2+(ZctgpsBA -z4)2)
[0080]
20
Next, usmg the obtained results, a test on a master base station 1s
executed.
[0081]
The difference between the positioning position and the measured
position on the master base station obtained by the above process is
compared with a predetermined threshold THmaster·
Master base station A
When 1'1ctgpsA < THmaster, the master base station A passes the test.
25 Master base station B
When 1'1ctgpsB < THmaster, the master base station B passes the test.
[0082]
The threshold THmaster may be properly determined so as to reflect
the precision of the positioning. For example, it may be determined on
25
the basis of the PDOP (Position Dilution of Precision) reflecting the
disposition state of the GPS satellite and the number of GPS satellites.
[0083]
It IS assumed now that "r" IS an amount which IS made
5 non-dimensional by dividing a system for the three-dimensional error by
typical length. In this case, with reference to the Maxwell-Boltzmann
distribution as a probability distribution function on "r" expressed by the
following equation (1 ), the threshold THmaster may be determined on the
basis of maximum allowable false-alarm probability, maximum allowable
10 detection failure probability, standard deviation of an error at fault-free
time, or the like.
[0084]
In the case where a master base station fails the test, to select a
proper master base station, the failed master base station and the base
15 station to be tested are replaced. Since selection of a master base station
is based on a result of the point positioning, the operation is a process of
eliminating the possibility that the difference between the point
positioning and the measured position becomes small by chance.
20
25
[0085]
When any one of the master base stations fails the test, the failed
master base station and a base station to be tested having the smallest
difference between a result of point positioning and a measured position
among base stations to be tested are replaced.
[0086]
When both of the master base stations fail the test, both of the
master base stations and two base stations to be tested are replaced.
Although the exemplary embodiment relates to the configuration of the
DGPS including the four master base stations, in the case where the
number of master base stations is larger than four, the base station to be
26
tested having the smallest difference between the result of point
positioning and the measured position and the base station to be tested
having the next smallest difference are replaced with the two master base
stations.
5 [0087]
10
After replacing the master base stations, the DGPS correction value
in each of the master base stations is calculated, and the above-described
process is repeated.
[0088]
In the case where a failure occurs in a base station and observation
data includes an error, a DGPS correction value calculated based on the
observation data also includes an error. Consequently, for example, when
a failure occurs in the master base station A, CA as a DGPS correction
value by the master base station A also includes an error. In a positioning
15 position by C8 of the master base station A, an error included in
20
observation data from the master base station A is reflected. In a
positioning position by CA of the master base station B, an error included
in the DGPS correction value CA by the master base station A is reflected.
[0089]
Therefore, in the case where the master base station A fails the test,
the master base station A is replaced with one of base stations to be tested,
the test process is performed, and the master base station fails again the
test, the master base station A may be taken back, and the master base
station B may be replaced.
25 [0090]
Similarly, also in the case where both of the master base stations
fail, there is the possibility that a failure occurs only in one of the master
base stations, so that any one of the master base stations may be taken back
depending on a result of the test process after replacing the master base
27
stations.
[0091]
Subsequently, the difference between the DGPS positioning result
and the measured position in a base station to be tested is calculated as a
5 three-dimensional distance.
[0092]
The difference between positioning position by CA of the base
station X to be tested and measured position
LlctgpsXA = ~ ( (XdgpsXA -X3)2+(y dgpsXA -y3)2+( ZctgpsXA -z3)2
)
10 The difference between positioning position by C8 of the base station X to
be tested and measured position
LlctgpsXB = ~ ( (XctgpsXB-X3)2+(y dgpsXB-Y3) 2+( ZctgpsXB-Z3) 2
)
The difference between positioning position by CA of the base station Y to
be tested and measured position
15 LlctgpsYA = ~((XctgpsYA-XI) 2 +(ydgpsYA-yi) 2 +(ZdgpsYA-ZI) 2 )
20
The difference between positioning position by CA of the base station X to
be tested and measured position
LlctgpsYB = ~ ( (XdgpsYB-X I ) 2+(y dgps YB-Y I ) 2+(ZdgpsYB-Z 1) 2
)
[0093]
By using these differences, a test on a base station to be tested IS
executed.
[0094]
When (LlctgpsXA < THtest) and (LlctgpsXB < THtest) are satisfied, the base
station X to be tested fails. In the other case, the base station X to be
25 tested passes the test.
When (LlctgpsYA < THtest) and (LlctgpsYB <; THtest) are satisfied, the base
station Y to be tested fails. In the other case, the base station Y to be
tested passes the test.
[0095]
5
28
The threshold THtest. like THmaster, may be properly determined so
as to reflect the precision of the positioning. For example, it may be
determined on the basis of the PDOP (Position Dilution of Precision)
reflecting the disposition state of the GPS satellite and the number of GPS
satellites. It is assumed now that "r" is an amount which is made
non-dimensional by dividing a system for the three-dimensional error by
typical length. In this case, with reference to the Maxwell-Boltzmann
distribution as a probability distribution function on "r", the threshold
THtest may be determined on the basis of maximum allowable false-alarm
10 probability, maximum allowable detection failure probability, standard
deviation of an error at fault-free time, or the like.
[0096]
As a result of the process, correction value information transmitted
from the correction value processing device 401 to the broadcast
15 transmitting device 501 includes a DGPS correction value of a base station
which passed the test.
[0097]
According to the method of detecting the state of a base station in a
differential GPS according to the exemplary embodiment, a GPS signal is
20 received from a GPS satellite, and occurrence of an abnormal state of a
base station correcting the GPS signal on the basis of the position
information of itself can be detected with high precision. That is, by
testing the master base station itself, a base station referred to can be
trusted as a base station operating normally. Consequently, based on
25 observation data from the base station determined to operate normally, an
abnormal state of a base station having the possibility of occurrence of
abnormality can be det~cted. Therefore, even when abnormality occurs
in a plurality of base stations, the abnormal state can be detected with high
precision. There is also no possibility that occurrence of abnormality in
29
a base station which is operating normally is determined erroneously.
[0098]
By setting a threshold in consideration of the number and
disposition of GPS satellites, the state is abnormal or normal can be
5 determined with higher precision.
[0099]
Although an abnormal state of a base station is detected by usmg
correction value information in a differential GPS in the exemplary
embodiment of the invention, the invention is not limited to the case.
10 [0100]
The present invention is preferably applied, in a positioning system
of receiving a signal from a signal source which periodically generates
information of time and position of itself and estimating the position of the
system itself, to detection of an abnormal state of a fixed base station,
15 which is referred to in a process of generating correction information for
the signal.
[0101]
Although the example of mounting the rece1vmg device in an
aircraft was described in the exemplary embodiment, the invention is not
20 limited to the exemplary embodiment. The receiving device may be
mounted in a ship or held by a car or a pedestrian. Although correction
value information is provided as VHF airwaves to the receiving device in
the exemplary embodiment, the invention is not limited to the exemplary
embodiment. The correction value information may be transmitted by
25 radio waves in other frequency bands or by wire. Further, the present
invention can be also applied to a positioning system in water.
[0102]
An apparatus executing the processing operation may be configured
by storing a program for executing the processing operation in a
30
computer-readable recording medium, distributing it, and installing the
program into a computer. Examples of the computer-readable recording
medium include a flexible disk, a CD-ROM (Compact Disk Read-Only
Memory), and MO (Magneto-Optical disk).
5 [0103]
Second Exemplary Embodiment
A second exemplary embodiment of the present invention will be
described with reference to the drawings.
[0104]
10 The configuration of the differential GPS 101 in the second
exemplary embodiment of the present invention is simila.r to the example
of the configuration of the differential GPS 101 in the first exemplary
embodiment illustrated m Fig. 1. A configuration example of the
correction value processmg device 401 m the second exemplary
15 embodiment of the present invention is also similar to that of the
correction value processing device 401 in the first exemplary embodiment
illustrated in Fig. 3.
[0 1 05]
Fig. 4 is a diagram illustrating a configuration example of the data
20 processing unit 403 included in the correction value processing device 401
in the second exemplary embodiment of the invention.
[0 1 06]
The data processmg unit 403 includes a first positioning position
calculating unit 406, a master base station selecting unit 407, a master base
25 station correction value calculating unit 408, a second positioning position
calculating unit 409, and an abnormality determining unit 410.
[0 1 07]
The first positioning position calculating unit 406 obtains a first
positioning position of a base station on the basis of a signal received from
31
a satellite by the base station. The first positioning position calculating
unit 406 performs point positioning on the base stations 301 to 304. As
described in the first exemplary embodiment, the first positioning position
calculating unit 406 uses, as point positioning, GPS signals from the n
5 pieces of the GPS satellites 201 to 20n and obtains three-dimensional
coordinate values of the positioning positions of the base stations 301 to
304.
[0 1 08]
The master base station selecting unit 407 selects predetermined
10 number of master base stations in ascending order of the distance between
preliminarily given position information (measured position) of a base
station and a first positioning position obtained by the first positioning
position calculating unit 406. As described in the first exemplary
embodiment, the. master base station selecting unit 407 obtains, as a
15 three-dimensional distance, the difference between the positioning position
and the measured position on each of the base stations 3 01 to 304 and
calculates the small/large relations on the differences. On the basis of
the calculated small/large relations, the master base station selecting unit
407 selects, as master base stations, for example, the base station having
20 the smallest difference and the base station having the next smallest
difference.
[0 1 09]
On the basis of a signal received from a satellite by a master base
station, the master base station correction value calculating unit 408
25 generates a correction value of the master base station. The correction
value of the master base station is, for example, a DGPS correction value
in the first exemplary embodiment.
[0110]
Base stations other than the master base stations correct the first
32
positioning position of the base stations other than the master base stations
by the correction value of the master base station, and the second
positioning position calculating unit 409 obtains a second positioning
position of a base station other than the master base station. The second
5 positioning position calculating unit 409 applies the correction value of
each of the master base stations to the first positioning position of the base
station other than the master base stations, thereby obtaining the second
positioning position. That is, the second positioning position calculating
unit 409 obtains second positioning positions only by the number of master
10 base stations.
[0111]
When the distance between the position according to preliminarily given
position information of a base station other than the master base stations
and the second positioning position is larger than the first threshold, the
15 abnormality determining unit 410 determines that the base station other
than the master base stations is in an abnormal state. The determination
by the abnormality determining unit 401 that a base station other than the
master base station is in an abnormal state is performed, for example, on
the basis of the pass/fail determination logic in Table 1 in the first
20 exemplary embodiment.
[0112]
Fig. 5 is a flowchart illustrating an operation example of the
correction value processing device 401 m the second exemplary
embodiment of the present invention.
25 [0 113]
The data receivmg unit 402 in the correction value processing
device 401 receives observation data from the base stations 301 to 304
which received the GPS signals generated from the GPS satellites 201 to
20n (step S501).
33
[0114]
Next, the data processmg unit 403 m the correction value
processing device 401 measures the position of each of the base stations
3 01 to 3 04 on the basis of the observation data (point positioning) to obtain
5 a first positioning distance (step S502).
[0115]
The data processmg unit 403 selects predetermined number of
master base stations in ascending order of the distance between position
information which is preliminarily given of the base station (measured
10 position) and the first positioning position (step S503).
[0116]
On the basis of the observation data obtained from the master base
station and the value of the measured position, the data processing unit 403
calculates the correction value of the master base station (step S504).
15 [0117]
Base stations other than the master base stations correct the first
positioning position of the base stations other than the master base stations
by the correction value of the master base station and, thereby obtaining a
second positioning position of a base station other than the master base
20 station by the data processing unit 403 (step S505).
[0118]
When the distance between the position according to preliminarily
gtven position information of a base station other than the master base
stations and the second positioning position is larger than the first
25 threshold, the data processing unit 403 determines that the base station
other than the master base stations is in an abnormal state (step S506).
[0119]
According to the method of detecting a state of a base station in a
differential GPS according to the exemplary embodiment, a GPS signal is
5
10
34
received from a GPS satellite and occurrence of an abnormal state of a base
station which corrects the GPS signal on the basis of position information
of itself can be detected.
[0 120]
In the state detecting method, by setting a threshold m
consideration of the number and disposition of GPS satellites, whether a
base station is abnormal or normal can be determined with high precision.
[0121]
Third Exemplary Embodiment
A third exemplary embodiment of the present invention will be
described with reference to the drawings.
[0122]
In the third exemplary embodiment of the present invention, a base
station is set as a master base station when the distance between
15 preliminarily given position information (measured position) of the base
station and a first positioning position of the base station lies m a
predetermined range. That is, in the third exemplary embodiment of the
invention, by using the absolute value of the distance between the
measured position of a base station and the first positioning position of the
20 base station, a master base station is selected.
[0 123]
25
The configuration of the differential GPS 101 m the third
exemplary embodiment of the present invention 1s similar to the example
of the configuration of the differential GPS 101 in the first exemplary
embodiment illustrated in Fig. 1. A configuration example of the
correction value processing device 401 in the third exemplary embodiment
of the present invention is also similar to that of the correction value
processing device 401 in the first exemplary embodiment illustrated in Fig.
3. Further, a configuration example of the correction value processing
5
35
device 401 in the third exemplary embodiment of the invention is similar to
that of the data processing unit 403 in the second exemplary embodiment
illustrated in Fig. 4.
[0124]
In the third exemplary embodiment of the present invention, the
master base station selecting unit 407 selects, as a master base station, a
base station when the distance between preliminarily given position
information (measured position) of the base station and a first positioning
position of the base station lies in a predetermined range.
10 [0125]
Three-dimensional coordinate values of the first positioning
position of a base station obtained by point positioning are described as
follows.
[0 126]
15 Base station 301: (Xsal, Ysal, Zsai)
Base station 302: (Xsa2, Ysa2, Zsa2)
Base station 303: (Xsa3, Ysa3, Zsa3)
Base station 304: (Xsa4, Ysa4, Zsa4)
[0127]
20 The three-dimensional coordinate values of the measured positions
for the base stations 301 to 304 are described as follows.
[0 128]
Base station 301: (x1, YI, z!)
Base station 302: (x2, y2, z2)
25 Base station 303: (x3, y3, z3)
Base station 304: (x4, y4, z4)
[0 129]
From the coordinate values, the master base station selecting unit
407 obtains, as the third-dimensional distance, the distance between the
36
first positioning position and the measured position on each of the base
stations 301 to 304.
[0130]
Base station 301: L1sal = v'(xsal-xi) 2+(ysal-yi) 2+(zsai-ZI)2)
5 Base station 302: L1sa2 = v'(xsa2-X2)2+(Ysa2-Y2)2+(zsa2-Z2) 2)
Base station 303: L1sa3 = v'(xsa3-X3)2+(Ysa3-Y3)2+(zsa3-Z3) 2)
Base station 304: L1sa4 = v'(xsa4-X4)2+(Ysa4-Y4)2+(zsa4-Z4) 2)
[0131]
After that, the master base station selecting unit 407 determines
10 whether each of the distances L1sal, L1sa2, L1sa3, and L1sa4 between the first
positioning position obtained and the measured position lies in a
predetermined threshold (predetermined range) or not.
[0132]
The master base station selecting unit 407 selects, as a master base
15 station, a base station corresponding to L1saJ, L1sa2, L1sa3, or L1sa4 which is
equal to or less than the predetermined threshold as a result of the
determination. For example, when L1sai as the distance of the base station
301 and L1sa2 as the distance ofthe base station 302 lie in the predetermined
range, the master base station selecting unit 407 selects the base stations
20 3 01 and 3 02 as master base stations.
[0133]
In the case where there is no "distance" equal to or less than the
predetermined threshold (predetermined range) in L1sal, L1sa2, L1sa3, and L1sa4
as a result of the determination, the master base station selecting unit 407
25 may increase the predetermined threshold (expand the predetermined
range) and perform the determination again. In this case, the master base
station selecting unit 407 may increase the predetermined threshold
(expand the predetermined range) each time the determination is performed
and repeatedly execute the determination until the master base station can
be selected.
[0134]
37
In the case where there is no "distance" equal to or less than the
predetermined threshold (predetermined range) in ~sal, ~sa2, ~sa3, and ~sa4
5 as a result of the determination, the master base station selecting unit 407
may select a master base station on the basis of the small/large relations of
the distance between the first positioning position and the measured
position in a manner similar to the first exemplary embodiment.
[0135]
10 In the case where there is no "distance" equal to or less than the
predetermined threshold (predetermined range) in ~sal, ~sa2, ~sa3, and ~sa4
as a result of the determination, the master base station selecting unit 407
may not select a master base station. In this case, without executing the
following process, the correction value processing device 401 may finish
15 the process.
[0136]
On the other hand, when all of ~sal, ~sa2, ~sa3, and ~sa4 are equal to
or less than the predetermined threshold (predetermined range) as a result
of the determination, the master base station selecting unit 407 may
20 decrease the predetermined threshold (narrow the predetermined range)
and perform the determination again. In this case, the master base station
selecting unit 407 may decrease the predetermined threshold (narrow the
predetermined range) each time the determination is performed and
repeatedly execute the determination until a base station other than the
25 master base station comes to exist.
[0 13 7]
In the case where all of ~sal, ~sa2, ~sa3, and ~sa4 are equal to or less
than the predetermined threshold (predetermined range) as a result of the
determination, the master base station selecting unit 407 may select a
38
master base station on the basis of the small/large relations of the distance
between the first positioning position and the measured position in a
manner similar to the first exemplary embodiment.
[0138]
5 In the case where all of L'lsa!, L'lsa2, L'lsa3, and L'lsa4 are equal to or less
than the predetermined threshold (predetermined range) as a result of the
determination, the master base station selecting unit 407 may select all of
the base stations as master base stations. In this case, the correction
value processing device 401 does not execute a process of determining
10 whether a base station other than the master base stations is in an abnormal
state or not.
[0139]
In the master base station selecting unit 407, the predetermined
range as a condition for selecting a base station as a master base station
15 can be changed according to, for example, a request of the user (such as an
administrator). In this case, the user (such as an administrator) can
adjust a condition of selecting a master base station by setting the
predetermined range in consideration of the number or disposition of base
stations. In the case where the predetermined range is set wide, even a
20 base station whose distance between the first positioning position and the
measured position is long to a certain extent is selected as a master base
station. In this case, a correction value of the master base station
becomes large and, as a result, a correction amount of the first positioning
position of a base station other than the master base station also becomes
25 large. The second positioning position of a base station other than the
master base station is a value obtained by correcting the first positioning
position of the base station other than the master base station by the
correction value of the master base station. That is, when the correction
value of the master base station is large, the second positioning position of
39
a base station other than the master base station becomes a value obtained
by largely correcting the first positioning position.
[0 140]
When the first positioning position Is corrected largely, the
5 correction amount of an error in DGPS positioning becomes large, so that
the first positioning position becomes close to the measured position.
Therefore, the possibility that the distance between the measured position
of a base station other than a master base station and the second
positioning position becomes larger than the first threshold decreases.
10 [0141]
The abnormality determining unit 410 performs determination , for
example, on the basis of the pass/fail determination logic of Table 1 in the
first exemplary embodiment. In this case, when a base station passes in
determination with a correction value in one master base station, the
15 abnormality determining unit 410 determines that the base station passes in
overall determination. Therefore, when a base station whose distance
between the first positioning position and the measured position is long to
a certain degree is selected as a master base station, the correction value
becomes large, and the case that the abnormality determining unit 410
20 determines that a base station other than the master base station passes
mcreases. As a result, the number of base stations other than master base
stations determined by the abnormality determining unit 410 that they are
in an abnormal state decreases. In other words, by widening the
predetermined range, when an error is small to a certain degree, the
25 abnormal state determining unit 410 determines that base stations other
than a master base station are normal.
[0 142]
On the other hand, in the case of setting the predetermined range
narrow, a base station whose distance between the first positioning
40
position and the measured position is short is selected as a master base
station. As a result, the number of base stations other than master base
stations determined by the abnormality determining unit 410 that they are
in an abnormal state increases. In other words, by narrowing the
5 predetermined range, even if an error is small, the abnormality determining
unit 410 determines that base stations other than a master base station are
abnormal.
[0143]
That is, in the third exemplary embodiment of the present invention,
10 by changing the predetermined range as a condition for selecting a base
station as a master base station, the precision of determination of whether a
base station other than a master base station is abnormal or normal can be
flexibly adjusted.
15
[0144]
Fig. 6 is a flowchart illustrating an operation example of the
correction value processing device 401 in the third exemplary embodiment
of the present invention.
[0 145]
The data receiving unit 402 in the correction value processing
20 device 401 receives observation data from the base stations 301 to 304
which received GPS signals generated from the GPS satellites 201 to 20n
(step S60 1 ).
[0 146]
On the basis of the observation data, the data processing unit 403 in
25 the correction value processing device 401 measures the position of each
of the base stations 301 to 304 (point positioning) to obtain a first
positioning distance (step S602).
[0 14 7]
Subsequently, the data processing unit 403 selects, as a master base
5
41
station, a base station when the distance between preliminarily given
position information (measured position) of the base station and the first
positioning position of the base station lies in a predetermined range from
the base stations 301 to 304 (step S603).
On the basis of the observation data and the value of the measured
position obtained from the master base station, the data processing unit
403 calculates the correction value of the master base station (step S604).
[0 148]
In the data processing unit 403, a base station other than a master
10 base station corrects the first positioning position of the base station other
than the master base station by the correction value of the master base
station, thereby obtaining a second positioning position of the base station
other than the master base station (step S605).
15
[0 149]
When the distance between the position by preliminarily given
position information of a base station other than a master base station and
the second positioning position is larger than a first threshold, the data
processing unit 403 determines that the base station other than the master
base station is in an abnormal state (step S606).
20 [0 15 0]
As described above, m the state detecting method of the third
exemplary embodiment of the present invention, a base station is
determined as a master base station when the distance between
preliminarily given position information (measured position) of the base
25 station and a first positioning position of the base station lies in a
predetermined range. In the state detecting method, by setting the
predetermined range in consideration of the number and disposition of base
stations, a condition of selecting a master base station can be adjusted.
As a result, in the state detecting method, the precision of determination of
42
whether a base station other than the master base station IS abnormal or
normal can be changed flexibly.
[0151]
Although a part or all of the foregoing exemplary embodiments can
5 be also described as the following supplementary notes, the present
invention is not limited to the below.
[0152]

A state detecting method of detecting an abnormal state of a base
10 station in a positioning system having a satellite and a base station,
including:
obtaining a first positioning position of the base station on the basis
of a signal received from the satellite by the base station;
selecting predetermined number of master base stations m
15 ascending order of a distance between preliminarily given position
information of the base station and the first positioning position of the
base station;
20
generating a correction value of the master base station on the basis
of a signal received from the satellite by the master base station;
obtaining a second positioning position of a base station other than
the master base station by correcting the first positioning position of the
base station other than the master base station with the correction value of
the master base station by the base station other than the master base
station; and
25 determining that the base station other than the master base station
IS m an abnormal state when the distance between a position by
preliminarily given position information of the base station other than the
master base station and the second positioning position is larger than a
first threshold.
43
[0153]

A state detecting method of detecting an abnormal state of a
plurality of base stations in a positioning system having a satellite and the
5 plurality of base stations, including
obtaining a first positioning position of the base station on the basis
of a signal received from the satellite by the base station;
selecting, as a master base station, a base station whose distance
between preliminarily given position information of the base station and
10 the first positioning position of the base station lies in a predetermined
range;
generating a correction value of the master base station on the basis
of a signal received from the satellite by the master base station;
obtaining a second positioning position of a base station other than
15 the master base station by correcting the first positioning position of the
base station other than the master base station with the correction value of
the master base station by the base station other than the master base
station; and
determining that the base station other than the master base station
20 IS m an abnormal state when the distance between a position by
preliminarily given position information of the base station other than the
master base station and the second positioning position is larger than a
first threshold.
[0154]
25
The state detecting method described in the supplementary note 1 or
2, wherein the correction value of the master base station includes an
ionosphere delay amount and a troposphere delay amount for the master
base station.
44
[0155]

The state detecting method described in any of the supplementary
notes 1 to 3, wherein a correction value of the master base station is a
5 value obtained by subtracting the first positioning position obtained by
executing a smoothing process on the pseudo range between the master
base station and the satellite from the preliminarily given position of the
master base station.
[0156]
10
The state detecting method described in any of the supplementary
notes 1 to 4, wherein the positioning system includes the plurality of
master base stations,
wherein the correction value used to correct the pseudo range of a
15 base station other than the mater base station is an average value of the
correction values generated by the plurality of master base stations.
[0157]

The state detecting method described in any of the supplementary
20 notes 1 to 5, wherein the positioning system has a first master base station
and a second master base station,
wherein a second positioning position of the first master base
station is obtained, which is derived by correcting a pseudo range between
the first master base station and the satellite obtained on the basis of a
25 signal received from the satellite by the first master base station with a
correction value of the second master base station;
when the distance between a position by preliminarily given
position information of the first master base station and the second
positioning position of the first master base station is larger than a second
45
threshold, it is determined that the first master base station IS In an
abnormal state; and
when it is determined that the first master base station is in an
abnormal state, one of base stations other than the plurality of master base
5 stations is selected as the first master base station.
[0158]

The state detecting method described in any of the supplementary
notes 1 to 6, wherein a satellite transmitting a signal to be received is
10 selected from the plurality of satellites.
[0159]

The state detecting method described in the supplementary note 7,
wherein as the satellite transmitting the signal to be received, a satellite
15 whose elevation angle is larger than a predetermined angle or a satellite
which can be seen ~~om all of base stations included in the positioning
system is selected from the plurality of satellites.
20
25
[0 160]

The state detecting method described in any of the supplementary
nodes 1 to 8, wherein the first threshold is determined with reference to a
predetermined probability distribution function.
[0161]

The state detecting method described in any of the supplementary
notes 1 to 9, wherein the first threshold is determined on the basis of the
number of the satellites and a disposition state of the satellites.
[0162]

46
A.correction value processing device including:
data receiving means receiving a signal received from a satellite by
a base station;
first positioning position calculating means calculating a first
5 positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting predetermined
number of master base stations in ascending order of a distance between
preliminarily given position information of the base station and the first
10 positioning position of the base station;
master base station correction value calculating means generating a
correction value of the master base station on the basis of a signal received
from the satellite by the master base station;
second positioning position calculating means calculating a second
15 positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
the base station other than the master base station; and
abnormality determining means determining that the base station
20 other than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
position is larger than a first threshold.
[0163]
25
A correction value processing device including:
data receiving means receiving a signal received from a satellite by
a base station;
first positioning position calculating means calculating a first
47
positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting, as a master base
station, a base station whose distance between preliminarily given position
5 information of the base station and the first positioning position of the
base station lies in a predetermined range;
10
15
master base station correction value calculating means generating a
correction value of the master base station on the basis of a signal received
from the satellite by the master base station;
second positioning position calculating means calculating a second
positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
the base station other than the master base station; and
abnormality determining means determining that the base station
other than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
position is larger than a first threshold.
20 [0164]

The correction value processmg device described m the
supplementary note 11 or 12, wherein the correction value of the master
base station includes an ionosphere delay amount and a troposphere delay
25 amount for the master base station.
[0 165]

The correction value processmg device described in any of the
supplementary notes 11 to 13, further including correction value
48
transmitting means transmitting the correction value generated by the data
processing means to a receiving device estimating the position of itself on
the basis of a signal received from the satellite.
[0 166]
5
A positioning system having a satellite, a base station, and a
correction value processing device, wherein the correction value
processing device includes:
first positioning position calculating means calculating a first
10 positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting predetermined
number of master base stations in ascending order of a distance between
preliminarily given position information of the base station and the first
15 positioning position of the base station;
master base station correction value calculating means generating a
correction value of the master base station on the basis of a signal received
from the satellite by the master base station;
second positioning position calculating means calculating a second
20 positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
the base station other than the master base station; and
abnormality determining means determining that the base station
25 other than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
position is larger than a first threshold.
[0167]
49

A positioning system having a satellite, a base station, and a
correction value processmg device, wherein the correction value
processing device includes:
5 first positioning position calculating means calculating a first
positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting, as a master base
station, a base station whose distance between preliminarily given position
10 information of the base station and the first positioning position of the
base station lies in a predetermined range;
15
20
master base station correction value calculating means generating a
correction value of the master base station on the basis of a signal received
from the satellite by the master base station;
second positioning position calculating means calculating a second
positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
the base station other than the master base station; and
abnormality determining means determining that the base station
other than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
position is larger than a first threshold.
25 [0 16 8]

The positioning system described in the supplementary note 15 or
16, wherein a correction value of the master base station includes an
ionosphere delay amount and a troposphere delay amount for the master
base station.
[0 169]

50
The positioning system described in any of the supplementary notes
5 15 to 17, further including a receiving device estimating position of itself
on the basis of a signal received from the satellite,
wherein the correction value processing device further includes
correction value transmitting means transmitting the correction value
generated by the data processing unit to the receiving device.
10 [0170]

A storage medium storing a program for detecting an abnormal state
of a base station in a positioning system having a satellite and the base
station, including:
15 a process of calculating a first positioning position of the base
station on the basis of the signal received by the data receiving means;
a process of selecting predetermined number of master base stations
m ascending order of a distance between preliminarily given position
information of the base station and the first positioning position of the
20 base station;
a process of generating a correction value of the master base station
on the basis of a signal received from the satellite by the master base
station;
a second positioning position calculating process of calculating a
25 second positioning position of a base station other than the master base
station by correcting the first positioning position of the base station other
than the master base station with the correction value of the master base
station by the base station other than the master base station; and
a process of determining that the base station other than the master
51
base station IS m an abnormal state when the distance between a position
by preliminarily given position information of the base station other than
the master base station and the second positioning position is larger than a
first threshold.
5 [0171]

A storage medium storing a program for detecting an abnormal state
of a base station in a positioning system having a satellite and the base
station, including:
10 a process of calculating a first positioning position of the base
station on the basis of the signal received by the data receiving means;
a process of selecting, as a master base station, a base station whose
distance between preliminarily given position information of the base
station and the first positioning position of the base station lies In a
15 predetermined range;
a process of generating a correction value of the master base station
on the basis of a signal received from the satellite by the master base
station;
a second positioning position calculating process of calculating a
20 second positioning position of a base station other than the master base
station by correcting the first positioning position of the base station other
than the master base station with the correction value of the master base
station by the base station other than the master base station; and
a process of determining that the base station other than the master
25 base station is in an abnormal state when the distance between a position
by preliminarily given position information of the base station other than
the master base station and the second positioning position is larger than a
first threshold.
[0 1 72]
52

The storage medium storing a program described m the
supplementary note 19 or 20, wherein a correction value of the master base
station includes at least an ionosphere delay amount and a troposphere
5 delay amount for the master base station.
[0173]

A state detecting method of detecting an abnormal state of a base
station in a positioning system having a satellite and a base station,
10 including:
obtaining a first positioning position of the base station on the basis
of a pseudo range between the base station and the satellite obtained on the
basis of a signal received from the satellite by the base station;
selecting predetermined number of master base stations m
15 ascending order of a distance between a position by preliminarily given
position information of the base station and the first positioning position
of the base station;
20
generating a correction value of the master base station on the basis
of the signal received from the satellite by the master base station;
obtaining a second positioning position of a base station other than
the master base station by correcting the pseudo range of the base station
other than the master base station with the correction value of the master
base station; and
determining that the base station other than the master base station
25 IS m an abnormal state when the distance between a position by
preliminarily given position information of the base station other than the
master base station and the second positioning position of the base station
other than the master base station is larger than a first threshold.
[0174]
53

The state detecting method described in the supplementary note 22,
wherein the correction value of the master base station includes an
ionosphere delay amount and a troposphere delay amount for the master
5 base station.
[0175]

The state detecting method described in the supplementary note 22
or 23, wherein a correction value of the master base station is a value
10 obtained by subtracting the first positioning position obtained by executing
a smoothing process on the pseudo range between the master base station
and the satellite from the preliminarily given position of the master base
station.
[0176]
15
The state detecting method described in any of the supplementary
notes 22 to 24, wherein the positioning system includes the plurality of
master base stations,
wherein the correction value used to correct the pseudo range of a
20 base station other than the mater base station is an average value of the
correction values generated by the plurality of master base stations.
[ 01 7 7]

The state detecting method described in any of the supplementary
25 notes 22 to 25, wherein the positioning system has a first master base
station and a second master base station,
wherein a second positioning position of the first master base
station is obtained, which is derived by correcting a pseudo range between
the first master base station and the satellite obtained on the basis of a
54
signal received from the satellite by the first master base station with a
correction value of the second master base station;
when the distance between a position by preliminarily g1ven
position information of the first master base station and the second
5 positioning position of the first master base station is larger than a second
threshold, it is determined that the first master base station is in an
abnormal state; and
when it is determined that the first master base station is in an
abnormal state, one of base stations other than the plurality of master base
10 stations is selected as the first master base station.
[0 1 78]

The state detecting method described in any of the supplementary
notes 22 to 26, wherein at the time of obtaining a first positioning position
15 of the base station, a satellite transmitting a signal to be received is
selected from the plurality of satellites.
[0 179]

The state detecting method described in the supplementary note 27,
20 wherein as the satellite transmitting the signal to be received, a satellite
whose elevation angle is larger than a predetermined angle or a satellite
which can be seen from all of base stations included in the positioning
system is selected from the plurality of satellites.
[0 180]
25
The state detecting method described in any of the supplementary
nodes 22 to 28, wherein the first threshold is determined with reference to
a predetermined probability distribution function.
[0181]
55

The state detecting method described in any of the supplementary
notes 22 to 29, wherein the first threshold is determined on the basis of the
number of the satellites and a disposition state of the satellites.
5 [0182]

A correction value processing device including:
data receiving means receiving a signal received from a satellite by
a base station; and
10 data processing means obtaining a first positioning position of the
base station on the basis of a pseudo range between the base station the
satellite derived on the basis of the signal received by the data receiving
means, selecting predetermined number of master base stations in
ascending order of a distance between a position by preliminarily given
15 position information of the base station and the first positioning position
of the base station, generating a correction value of the master base station
on the basis of a signal received from the satellite by the master base
station, obtaining a second positioning position of a base station other than
the master base station by correcting the pseudo range of the base station
20 other than the master base station with the correction value of the master
base station, and determining that the base station other than the master
base station is in an abnormal state when the distance between a position
by preliminarily given position information of the base station other than
the master base station and the second positioning position of the base
25 station other than the master base station is larger than a first threshold.
[0183]

The correction value processmg device described m the
supplementary note 31, wherein the correction value of the master base
5
56
station includes an ionosphere delay amount and a troposphere delay
amount for the master base station.
[0184]

The correction value
supplementary note 31 or
processing
32, further
device
including
described m the
correction value
transmitting means transmitting the correction value generated by the data
processing means to a receiving device estimating the position of itself on
the basis of a signal received from the satellite.
10 [0185]
15

A positioning system having a satellite, a base station, and a
correction value processing device, wherein the correction value
processing device includes:
data processing means obtaining a first positioning position of the
base station on the basis of a pseudo range between the base station and the
satellite derived on the basis of a signal received from the satellite by the
base station, selecting predetermined number of master base stations in
ascending order of a distance between a position by preliminarily given
20 position information of the base station and the first positioning position
of the base station, generating a correction value of the master base station
on the basis of a signal received from the satellite by the master base
station, obtaining a second positioning position of a base station other than
the master base station by correcting the pseudo range of the base station
25 other than the master base station with the correction value of the master
base station, and determining that the base station other than the master
base station is in an abnormal state when the distance between a position
by preliminarily given position information of the base station other than
the master base station and the second positioning position of the base
57
station other than the master base station is larger than a first threshold.
[0 186]

The positioning system described in the supplementary note 34,
5 wherein the correction value of the master base station includes an
ionosphere delay amount and a troposphere delay amount for the master
base station.
10
[0187]

The positioning system described in the supplementary note 34 or
35, further including a receiving device estimating position of itself on the
basis of a signal received from the satellite,
wherein the correction value processing device further includes
correction value transmitting means transmitting the correction value
15 generated by the data processing unit to the receiving device.
[0188]

A storage medium storing a program for detecting an abnormal state
of a base station in a positioning system having a satellite and the base
20 station, including:
a process of obtaining a first positioning position of the base
station on the basis of a pseudo range between the base station and the
satellite derived on the basis of a signal received from the satellite by the
base station;
25 a process of selecting predetermined number of master base stations
in ascending order of a distance between a position by preliminarily given
position information of the base station and the first positioning position
of the base station;
a process of generating a correction value of the master base station
58
on the basis of a signal received from the satellite by the master base
station;
a process of obtaining a second positioning position of a base
station other than the master base station by correcting the pseudo range of
5 the base station other than the master base station with the correction value
of the master base station; and
a process of determining that the base station other than the master
base station is in an abnormal state when the distance between a position
by preliminarily given position information of the base station other than
10 the master base station and the second positioning position of the base
station other than the master base station is larger than a first threshold.
[0189]

The storage medium storing a program described m the
15 supplementary note 3 7, wherein a correction value of the master base
station includes at least an ionosphere delay amount and a troposphere
delay amount for the master base station.
[0 190]
Although the state detecting method and the like of the present
20 invention have been described on the basis of the exemplary embodiments,
obviously, the invention is not limited to the exemplary embodiments and
can include various modifications, changes, and improvements in the
exemplary embodiments within the scope of the present invention and on
the basis of the fundamental technical idea of the present invention.
25 Within the scope of claims of the present invention, vanous disclosure
elements can be variously combined, replaced, or selected. Further
problems, objects, and expansion modes of the present invention will
become apparent also from the entire disclosure articles of the present
invention including the scope of claims.
5
59
[0191]
The present application claims priority based on Japanese Patent
Application No. 2013-035783 filed on February 26, 2013, the entire
disclosure of which is incorporated herein.
Industrial Applicability
[0192]
The present invention is not limited to the foregoing exemplary
embodiments but can be preferably applied to a positioning system using a
10 plurality of base stations.
Reference signs List
[0193]
101 differential GPS
15 201, 20n GPS satellite
301, 302, 303, 304 base station
401 correction value processing device
402 data receiving unit
403
20 404
data processing unit
data holding unit
405 correction value transmitting unit
406 first positioning position calculating unit
407
408
25 409
master base station selecting unit
master base station correction value calculating unit
second positioning position calculating unit
410 abnormality determining unit
501 broadcast transmitting device
601 receiving device

CLAIMS
1. A state detecting method of detecting an abnormal state of a base
station in a positioning system having a satellite and a base station,
5 compnsmg:
obtaining a first positioning P?Sition of the base station on the basis
of a signal received from the satellite by the base station;
selecting predetermined number of master base stations m
ascending order of a distance between preliminarily given position
10 information of the base station and the first positioning position of the
base station;
generating a correction value of the master base station on the basis
of a signal received from the satellite by the master base station;
obtaining a second positioning position of a base station other than
15 the master base station by correcting the first positioning position of the
base station other than the master base station with the correction value of
the master base station by the base station other than the master base
station; and
determining that the base station other than the master base station
20 IS m an abnormal state when the distance between a position by
preliminarily given position information of the base station other than the
master base station and the second positioning position is larger than a
first threshold.
25 2. A state detecting method of detecting an abnormal state of a
plurality of base stations in a positioning system having a satellite and the
plurality of base stations, comprising:
obtaining a first positioning position of the base station on the basis
of a signal received from the satellite by the base station;
61
selecting, as a master base station, a base station whose distance
between preliminarily given position information of the base station and
the first positioning position of the base station lies in a predetermined
range;
5 generating a correction value of the master base station on the basis
of a signal received from the satellite by the master base station;
obtaining a second positioning position of a base station other than
the master base station by correcting the first positioning position of the
base station other than the master base station with the correction value of
10 the master base station by the base station other than the master base
station; and
determining that the base station other than the master base station
IS In an abnormal state when the distance between a position by
preliminarily given position information of the base station other than the
15 master base station and the second positioning position is larger than a
first threshold.
3. The state detecting method according to claim 1 or 2, wherein the
correction value of the master base station includes an ionosphere delay
20 amount and a troposphere delay amount for the master base station.
4. The state detecting method according to any of claims 1 to 3,
wherein a correction value of the master base station is a value obtained by
subtracting the first positioning position obtained by executing a
25 smoothing process on the pseudo range between the master base station and
the satellite from the preliminarily given position of the master base
station.
5. The state detecting method according to any of claims 1 to 4,
62
wherein the positioning system includes the plurality of master base
stations,
wherein the correction value used to correct the pseudo range of a
base station other than the mater base station is an average value of the
5 correction values generated by the plurality of master base stations.
6. The state detecting method according to any of claims 1 to 5,
wherein the positioning system has a first master base station and a second
master base station,
10 wherein a second positioning position of the first master base
station is obtained, which is derived by correcting a pseudo range between
the first master base station and the satellite obtained on the basis of a
signal received from the satellite by the first master base station with a
correction value of the second master base station;
15 when the distance between a position by preliminarily g1ven
position information of the first master base station and the second
positioning position of the first master base station is larger than a second
threshold, it is determined that the first master base station is in an
abnormal state; and
20 when it is determined that the first master base station IS m an
abnormal state, one of base stations other than the plurality of master base
stations is selected as the first master base station.
7. The state detecting method according to any of claims 1 to 6,
25 wherein a satellite transmitting a signal to be received is selected from the
plurality of satellites.
8. The state detecting method according to claim 7, wherein as the
satellite transmitting the signal to be received, a satellite whose elevation
5
63
angle is larger than a predetermined angle or a satellite which can be seen
from all of base stations included in the positioning system is selected
from the plurality of satellites.
9. The state detecting method according to any of claims 1 to 8,
wherein the first threshold is determined with reference to a predetermined
probability distribution function.
10. The state detecting method according to any of claims 1 to 9,
10 wherein the first threshold is determined on the basis of the number of the
satellites and a disposition state of the satellites.
11. A correction value processing device comprising:
data receiving means receiving a signal received from a satellite by
15 a base station;
first positioning position calculating means calculating a first
positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting predetermined
20 number of master base stations in ascending order of a distance between
preliminarily given position information of the base station and the first
positioning position of the base station;
master base station correction value calculating means generating a
correction value of the master base station on the basis of a signal received
25 from the satellite by the master base station;
second positioning position calculating means calculating a second
positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
64
the base station other than the master base station; and
abnormality determining means determining that the base station
other than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
5 station other than the master base station and the second positioning
position is larger than a first threshold.
12. A correction value processing device comprising:
data receiving means receiving a signal received from a satellite by
10 a base station;
first positioning position calculating means calculating a first
,positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting, as a master base
15 station, a base station whose distance between preliminarily given position
information of the base station and the first positioning position of the
base station lies in a predetermined range;
master base station correction value calculating means generating a
correction value of the master base station on the basis of a signal received
20 from the satellite by the master base station;
second positioning position calculating means calculating a second
positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
master base station with the correction value of the master base station by
25 the base station other than the master base station; and
abnormality determining means determining that the base station
other than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
65
position is larger than a first threshold.
13. The correction value processing device according to claim 11 or 12,
wherein the correction value of the master base station includes an
5 ionosphere delay amount and a troposphere delay amount for the master
base station.
14. The correction value processmg device according to any of claims
11 to 13, further compnsmg correction value transmitting means
10 transmitting the correction value generated by the data processing means to
a receiving device estimating the position of itself on the basis of a signal
received from the satellite.
15. A positioning system having a satellite, a base station, and a
15 correction value processmg device, wherein the correction value
processing device comprises:
20
first positioning position calculating means calculating a first
positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting predetermined
number of master base stations in ascending order of a distance between
preliminarily given position information of the base station and the first
positioning position of the base station;
master base station correction value calculating means generating a
25 correction value of the master base station on the basis of a signal received
from the satellite by the master base station;
second positioning position calculating means calculating a second
positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
66
master base station with the correction value of the master base station by
the base station other than the master base station; and
abnormality determining means determining that the base station
other than the master base station is in an abnormal state when the distance
5 between a position by preliminarily given position information of the base
station other than the master base station and the second positioning
position is larger than a first threshold.
16. A positioning system having a satellite, a base station, and a
10 correction value processmg device, wherein the correction value
processing device comprises:
15
first positioning position calculating means calculating a first
positioning position of the base station on the basis of the signal received
by the data receiving means;
master base station selecting means selecting, as a master base
station, a base station whose distance between preliminarily given position
information of the base station and the first positioning position of the
base station lies in a predetermined range;
master base station correction value calculating means generating a
20 correction value of the master base station on the basis of a signal received
from the satellite by the master base station;
second positioning position calculating means calculating a second
positioning position of a base station other than the master base station by
correcting the first positioning position of the base station other than the
25 master base station with the correction, value of the master base station by
the base station other than the master base station; and
abnormality determining means determining that the base station
other than the master base station is in an abnormal state when the distance
between a position by preliminarily given position information of the base
67
station other than the master base station and the second positioning
position is larger than a first threshold.
17. The positioning system according to claim 15 or 16, wherein a
5 correction value of the master base station includes an ionosphere delay
amount and a troposphere delay amount for the master base station.
18. The positioning system according to any of claims 15 to 17, further
comprising a receiving device estimating position of itself on the basis of a
10 signal received from the satellite,
15
20
wherein the correction value processmg device further compnses
correction value transmitting means transmitting the correction value
generated by the data processing unit to the receiving device.
19. A storage medium storing a program for detecting an abnormal state
of a base station in a positioning system having a satellite and the base
station, comprising:
a process of calculating a first positioning position of the base
station on the basis of the signal received by the data receiving means;
a process of selecting predetermined number of master base stations
In ascending order of a distance between preliminarily given position
information of the base station and the first positioning position of the
base station;
a process of generating a correction value of the master base station
25 on the basis of a signal received from the satellite by the master base
station;
a second positioning position calculating process of calculating a
second positioning position of a base station other than the master base
station by correcting the first positioning position of the base station other
68
than the master base station with the correction value of the master base
station by the base station other than the master base station; and
a process of determining that the base station other than the master
base station is in an abnormal state when the distance between a position
5 by preliminarily given position information of the base station other than
the master base station and the second positioning position is larger than a
first threshold.
20. A storage medium storing a program for detecting an abnormal state
10 of a base station in a positioning system having a satellite and the base
station, comprising:
a process of calculating a first positioning position of the base
station on the basis of the signal received by the data receiving means;
a process of selecting, as a master base station, a base station whose
15 distance between preliminarily given position information of the base
station and the first positioning position of the base station lies m a
predetermined range;
a process of generating a correction value of the master base station
on the basis of a signal received from the satellite by the master base
20 station;
a second positioning position calculating process of calculating a
second positioning position of a base station other than the master base
station by correcting the first positioning position of the base station other
than the master base station with the correction value of the master base
25 station by the base station other than the master base station; and
a process of determining that the base station other than the master
base station is in an abnormal state when the distance between a position
by preliminarily given position information of the base station other than
the master base station and the second positioning position is larger than a
69
first threshold.
21. The storage medium storing a program according to claim 19 or 20,
wherein a correction value of the master base station includes at least an
5 ionosphere delay amount and a troposphere delay amount for the master
base station.