DESCRIPTION
Technical Field
[OOOl]
This invention relates to a position calculation method
of calculating a position using signals from positioning
satellites etc.
Background Art
[0002]
As a position calculation system using positioning
signals frompositioning satellites, a GPS (Global Positioning
System) is widely known and built in a cell phone, a car
navigation system, or the like as a position calculation
apparatus. In the GPS, orbital information (ephemeris or
almanac) superimposed on GPS satellite signals is acquired,
the positions of the satellites are specified, and thereby,
the position of the apparatus itself is calculated based on
pseudo ranges.
[0003]
At the first position calculation, the GPS does not
retain the ephemerides, and it is necessary to acquire the
ephemerides first. This takes several tens of seconds and the
time to first fix (TTFF) increases.
[0004]
There is a method of capturing satellites using an
almanac, however, the almanac is only available for capturing
the satellites, but not available for positioning due to a
problem of accuracy. Nonetheless, if the almanac can be early
acquired, the satellites can be early captured. Accordingly,
in NPL 1, a technology of transmitting almanac information
using L1-SAIF signals of quasi-zenith satellites (QZS) is
proposed.
Citation List
Non Patent Literature
[0005]
NPL 1 : SAKAI Takayasu, Transmitting Orbital Parameters
to Reduce Time to First Fix (TTFF) of GPS, IEICE TRANSACTIONS
on Communications Vol. J91-B, No. 4, The Institute of
Electronics, Information and Communication Engineers, April,
2008, pp. 479-486
Summary of Invention
Technical Problems
[0006]
However, in the above described technology of NPL 1, in
order to reduce the amount of data transmitted from the
quasi-zenith satellites, difference information of the
almanac is transmitted. Accordingly, a mechanism for storing
a dedicated almanac as reference of difference at the terminal
device side in advance is necessary. Further, the orbital
information to be transmitted is an almanac, and only the time
taken for capturing the satellites is reduced.
[0007]
The invention has been made in view of the circumstances
described above, and an object of the invention is to reduce
the time to first fix in position calculation based on signals
from positioning satellites.
Solution to Problems
[0008]
Afirst aspect ofthe invention is directedto aposition
calculation method including receiving positioning support
information containing at least information of a position and
a velocity of a positioning satellite from an artificial
satellite that transmits the positioning support information,
calculating orbital information of the positioning satellite
using the positioning support information, and calculating a
position of a receiver using a signal from the positioning
satellite and the orbital information.
[OOOS]
As another aspect of the invention, the invention may
be configured as a position calculation apparatus including
a receivingunit that receives positioning support information
containing at least information of a position and a velocity
of a positioning satellite from an artificial satellite that
transmits the positioning support information, an orbital
information calculation unit that calculates orbital
information ofthe positioning satellite usingthepositioning
support information, and a position calculation unit that
calculates a position using a signal from the positioning
satellite and the orbital'information.
[OOlO]
As a second aspect of the invention, the invention may
be configured as a position calculation method including
receivingpositioning support information containing at least
information of a position and a velocity of a positioning
satellite from a ground communication device that transmits
the positioning support information, calculating orbital
information ofthe positioning satelliteusingthepositioning
support information, and calculating a position of a receiver
using a signal from the positioning satellite and the orbital
information.
[OOll]
As another aspect of the invention, the invention may
be configured as a position calculation apparatus including
a receivingunitthatreceives positioning support information
containing at least information of a position and a velocity
of a positioning satellite from a ground communication device
that transmit st he positioning support information, an orbital
information calculation unit that calculates orbital
informationofthe positioning satelliteusingthepositioning
support information, and a position calculation unit that
calculates a position using a signal from the positioning
satellite and the orbital information.
According to the first aspect of the invention and the
like, the positioning support information transmitted fromthe
artificial satellite or the ground communication device is
received, the orbital information ofthe positioning satellite
is calculated using the received positioning support
information, and the position is calculated using the signal
from the positioning satellite and the calculated orbital
information of the positioning satellite. That is, the
orbital information of the positioning satellite is obtained
by the positioning support information from the other
artificial satellite or ground communication device than the
positioning satellite, and thus, the time to first fix may be
reduced.
[0013]
As a third aspect of the invention, the invention may
be configured as the position calculation method according to
the first or second aspect of the inventioni wherein the
informationofthepositionandthevelocityofthepositioning
s a t e l l i t e c o n t a i n e d i n t h e p o s i t i o n i n g support information is
information o f t h e p o s i t i o n a n d t h e velocityofthepositioning
s a t e l l i t e a t a given time.
[0014]
According t o t h e t h i r d aspect of t h e invention, t h e
information contained i n t h e received p o s i t i o n i n g support
information i s information of s i n g l e p o s i t i o n and v e l o c i t y .
Accordingly, comparedtothe casewhere t h e o r b i t a l information
(ephemeris o r the l i k e ) is received from t h e p o s i t i o n i n g
s a t e l l i t e , f o r example, t h e amount of memory f o r s t o r a g e of
t h e received information may be reduced.
[0015]
As a f o u r t h aspect of t h e i n v e n t i o n , t h e i n v e n t i o n may
be configured as t h e p o s i t i o n c a l c u l a t i o n m e t h o d according t o
any one o f t h e f i r s t t o t h i r d aspects o f t h e invention, wherein
t h e c a l c u l a t i n g t h e o r b i t a l information includes c a l c u l a t i n g
t h e o r b i t a l i n f o r m a t i o n u s i n g an equation ofmotion expressing
motion of a s a t e l l i t e o r b i t i n g t h e e a r t h and t h e p o s i t i o n and
t h e v e l o c i t y of t h e p o s i t i o n i n g s a t e l l i t e contained i n t h e
p o s i t i o n i n g support information.
[0016]
According t o t h e f o u r t h aspect of t h e i n v e n t i o n , t h e
o r b i t a l i n f o r m a t i o n o f t h e p o s i t i o n i n g s a t e l l i t e i s c a l c u l a t e d
u s i n g t h e e q u a t i o n o f m o t i o n e x p r e s s i n g m o t i o n o f t h e s a t e l l i t e
o r b i t i n g the e a r t h and t h e p o s i t i o n and t h e v e l o c i t y of t h e
p o s i t i o n i n g s a t e l l i t e contained i n t h e p o s i t i o n i n g support
information.
[0017]
As a f i f t h aspect of t h e invention, t h e i n v e n t i o n may
be configured as t h e p o s i t i o n c a l c u l a t i o n m e t h o d according t o
t h e f o u r t h aspect of t h e invention, wherein t h e p o ' s i t i o n i n g
s u p p o r t information f u r t h e r contains e a r t h o r i e n t a t i o n
information, t h e equation of motion is defined by an i n e r t i a l
coordinate system with r e f e r e n c e t o t h e e a r t h c e n t e r , t h e
p o s i t i o n a n d t h e v e l o c i t y c o n t a i n e d i n t h e p o s i t i o n i n g support
information a r e defined by a f i x e d coordinate system with
r e f e r e n c e t o t h e e a r t h center, and t h e c a l c u l a t i n g t h e o r b i t a l
information includes coordinate-transforming t h e p o s i t i o n a n d
t h e v e l o c i t y c o n t a i n e d i n t h e p o s i t i o n i n g s u p p o r t i n f o r m a t i o n
intoapositionandavelocityoftheinertialcoordinate system
using t h e e a r t h o r i e n t a t i o n information contained i n t h e
p o s i t i o n i n g support information.
[0018]
According t o t h e f i f t h aspect of t h e i n v e n t i o n , t h e
equation of motion expressing t h e s a t e l l i t e motion near t h e
e a r t h i s defined by t h e i n e r t i a l coordinate system with
r e f e r e n c e t o t h e e a r t h c e n t e r , t h e p o s i t i o n and t h e v e l o c i t y
contained i n t h e p o s i t i o n i n g support information a r e d e f i n e d
by t h e fixed coordinate system with r e f e r e n c e t o t h e e a r t h
center. Further, the artificial satellite or the ground
communication. device transmits the earth orientation
information containedinthe positioning support information.
Accordingly, the calculation ofthe orbital information ofthe
positioning satellite is performed after the coordinate
transformation of the position and the velocity contained in
the positioning support information into the position and the
velocity of the inertial coordinate system using the earth
orientation information contained in the positioning support
information.
[0019]
As a sixth aspect of the invention, the invention may
be configured as the position calculationmethod according to
any one ofthe first to fifth aspects ofthe invention, wherein
the calculating the orbital information includes obtaining a
parameter of an ephemeris of the positioning satellite.
[0020]
According to the sixth aspect of the invention, the
parameter of the ephemeris of the positioning satellite is
obtained as the orbital information.
[0021]
As a seventh aspect of the invention, the invention may
be configured as a position calculation method including
receivingpositioning support information containing at least
information -of a position and a velocity- of a positioning
satellite from an artificial satellite that transmits the
positioning support information, obtaining an orbital
function of the positioning satellite using an equation of
motion expressingmotion of a satellite orbiting the earth and
the position and the velocity of the positioning satellite
contained in the positioning support information, estimating
a satellite position of the positioning satellite using the
orbital function, and calculating a position of a receiver
using a signal fromthepositioning satellite andthe estimated
satellite position of the positioning satellite.
[0022]
As an eighth aspect of the invention, the invention may
be configured as a position calculation method including
receiving positioning support information containing at least
information of a position and a velocity of a positioning
satellite from a ground communication device that transmits
the positioning support information, obtaining an orbital
function of the positioning satellite using an equation of
motion expressing motion of a satellite orbiting the earth and
the position and the velocity of the positioning satellite
containedin the positioning support information, estimating
a satellite position of the positioning satellite using the
orbital function, and calculating a position of a receiver
usinga signalfromthepositioning satellite andthe estimated
satellite position of the positioning satellite.
LO0231
According to the seventh and eighth aspects of the
invention, the positioning support information transmitted
from the artificial satellite or the ground communication
device is received, the orbital function is obtained using the
equation of motion expressing the satellite motion near the
earth and the position and the velocity of the positioning
satellite contained in the received positioning support
information, the position of the positioning satellite is
estimatedusingtheobtainedorbitalfunction, andtheposition
is calculated using the signal fromthe positioning satellite
and the estimated satellite position of the positioning
satellite. That is, the satellite position ofthe positioning
satellite is obtained by the positioning support information
from the artificial satellite or the ground communication
device, and thus, the time to first fix may be reduced.
Brief Description of Drawings
[ 0 02 4 ]
[Fig. 11 Fig. 1 is a configuration diagram of a position
calculation apparatus.
[Fig. 21 Fig. 2 is a functional configuration diagram
of a baseband processing circuit part.
[Fig. 31 Fig. 3 is a flowchart of baseband processing.
[Fig. 41 Fig. 4 is a flowchart of baseband processing
in a modified example.
[Fig. 51 Fig. 5 shows amodifiedexamplewhentheposition
calculation apparatus receives positioning support
information from a ground communication device.
Description of Embodiments
[0025]
As below, embodiments ofthe invention will be explained
with reference to the drawings. Note that the embodiments to
which the invention is applicable are not limited to those.
[0026]
[Outline]
Fig. 1 is a configuration diagram of a position
calculation apparatus 1 of the embodiment. The position
calculation apparatus 1is a receiver that receives satellite
signals from. GPS satellites 3 and a quasi-zenith satellite 5
and calculates the position of the apparatus based on the
received satellite signals.
[0027]
In the embodiment, for the quasi-zenith satellite 5 as
an artificial satellite, a satellite of the quasi-zenith
satellites system project known as a Japanese satellite
positioning system is used. Further, in the embodiment, the
quasi-zenith satellite 5 transmits positioning support
information as information for supporting GPS positioning as
one of messages superimposed on the L1-SAIF signal as a
reinforcement signal in the sub-meter order. The positioning
support information includes satellite position and velocity
information and earth orientation parameters (EOP). The
satellite position and velocity information includes
positions rO and velocities vO at a certain time to and clock
errors of the respective GPS satellites 3. The earth
orientation parameters as earth orientation information
include UT1-UTC, length of day (LOD) , X-polar motion, X-polar
motion velocity, Y-polar motion, and Y-polar motion velocity.
[0028]
At the first position calculation (first positioning),
the position calculation apparatus 1 estimates ephemerides
(orbital information) of the GPS satellites 3 using the
positioning support information received from the
quasi-zenith satellite 5, and performs position calculation
(positioning) using the estimated ephemerides. After the
first position calculation, the apparatus continuously
receives the GPS satellite signals from the GPS satellites 3
and, when the acquisition of the ephemerides contained in the
GPS satellite signals is completed, switches the operation to
position calculation usingthe acquired ephemerides. In this
manner, reduction of TTFF is realized using the positioning
support information from the quasi-zenith satellite 5.
[0029]
[Principle]
The estimation of the ephemeris of the GPS satellite 3
based on the positioning support information received fromthe
quasi-zenith satellite 5 is explained.
[0030]
First, regarding the GPS satellite 3, an equation of
motion of the following formula (1) holds.
[0031]
[Formula 11
In the formula (I), m is a mass of the GPS satellite 3,
F is a force acting on the GPS satellite 3, and r is a position
oftheGPS satellite 3 attime t. Further, a is anacceleration
force acting on the GPS satellite 3 and given by the following
formula (2).
[Formula 21
In the formula (2), a, is acceleration of gravity, a,
1 is the gravitational pull of the moon, a,,, is gravitational
pull of the sun, a,,, is solar radiation pressure. That is,
the equation of motion expressing the motion of the satellite
orbiting the earth in outer space is determined by the formula
(1) and the formula ( 2 ) .
[0033]
Further, t h e equation of motion of t h e formula (1) is
numerically i n t e g r a t e d with t h e p o s i t i o n r ( t 0 ) = r O and t h e
v e l o c i t y v ( t 0 ) =vO a t t h e t i m e t o a s i n i t i a l v a l u e s , andthereby,
t h e p o s i t i o n r ( t ) of t h e GPS s a t e l l i t e 3 a t t i m e t, i . e . , an
o r b i t a l function expressing t h e s a t e l l i t e o r b i t is obtained
as the following formula (3) .
[0034]
1
I
I [Formula 31
The i n i t i a l values given here are t h e p o s i t i o n rO and
t h e v e l o c i t y vO of the GPS s a t e l l i t e 3 a t time t o contained
i n the p o s i t i o n i n g support information. I f t h e s a t e l l i t e
o r b i t is obtained, an ephemeris a d a p t i n g t o t h e s a t e l l i t e o r b i t
may be estimated.
Now, t h e above described equation of motion expressing
t h e motion of t h e s a t e l l i t e (formula (1)) is defined i n t h e
I e a r t h c e n t e r e d i n e r t i a l ( E C I ) coordinate systemas an i n e r t i a l
coordinate system with r e f e r e n c e t o the e a r t h c e n t e r . On t h e
o t h e r h a n d , t h e p o s i t i o n c a l c u l a t e d i n t h e p o s i t i o n c a l c u l a t i o n
apparatus 1 and the p o s i t i o n and t h e v e l o c i t y of t h e GPS
s a t e l l i t e 3 contained i n the p o s i t i o n i n g support information
t r a n s m i t t e d b y t h e quasi-zenith s a t e l l i t e 5 are d e f i n e d i n t h e
e a r t h centered e a r t h fixed (ECEF) coordinate system as a
coordinate s y s t e m f i x e d t o t h e e a r t h w i t h r e f e r e n c e t o t h e e a r t h
c e n t e r .
[0036]
Accordingly, f o r estimation of the s a t e l l i t e o r b i t ,
coordinate transformationbetween t h e e a r t h c e n t e r e d i n e r t i a l
( E C I ) coordinate system and t h e e a r t h centered e a r t h fixed
(ECEF) coordinate system i s necessary. As well known, a
coordinate t r a n s f o r m a t i o n m a t r i x Q between the e a r t h centered
i n e r t i a l ( E C I ) coordinate system and t h e e a r t h centered e a r t h
f i x e d (ECEF) coordinate system is given by t h e following
formulae ( 4 ) .
[0037]
[Formulae 41
In the formulae ( 4 ) , A i s a r o t a t i o n matrix of p o l a r motion,
B i s a r o t a t i o n matrix a t t h e s i d e r e a l time, C i s a r o t a t i o n
matrix of n u t a t i o n , and D is a r o t a t i o n matrix of precession.
These matrices A, B, C, D are determined by the time t and t h e
e a r t h o r i e n t a t i o n parameters (EOP) contained i n the
p o s i t i o n i n g support information. I n o t h e r words, t h e s e
matrices A, B, C, D are expressed by the e a r t h o r i e n t a t i o n
parameters and the coordinate transformation matrix Q is
determined.
[0038]
[Configuration of Positioning Apparatus]
The position calculation apparatus 1 includes a
satellite receiving antenna 10, a satellite signal receiving
unit 20, a host processing unit 30, an operation unit 31; a
display unit 32, a sound output unit 33, a clock unit 34, and
a memory unit 35.
[0039]
The satellite receiving antenna 10 is an antenna that
receives RF (Radio Frequency) signals containing the GPS
satellite signals transmitted from the GPS satellites 3 and
the quasi-zenith satellite signals (QZS satellite signals)
transmitted from the quasi-zenith satellite 5.
[0040]
The satellite signal receiving unit 20 has an RF
receiving circuit part 21 and a baseband processing circuit
part 22, and calculates the position of the position
c a l c u l a t i o n a p p a r a t u s 1 b a s e d o n t h e satellite signals received
by the satellite receiving antenna 10. Incidentally, the RF
receiving circuit part 21 and the baseband processing circuit
part 22 may be manufactured as separate LSIs (large scale
integrations) or as one chip.
[0041]
~ The RF receiving c i r c u i t p a r t 21 is a receiving c i r c u i t
f o r RF s i g n a l s . As a c i r c u i t configuration, f o r example, a
receiving c i r c u i t t h a t converts the RF s i g n a l s received by .the
s a t e l l i t e receiving antenna 10 i n t o d i g i t a l s i g n a l s using an
I
A/Dconverter andprocessesthedigitalsignalsmaybe employed,
o r t h e RF s i g n a l s received by the s a t e l l i t e receiving antenna
10 may be signal-processed as the analog s i g n a l s and f i n a l l y
A/D-converted, and thereby, the d i g i t a l s i g n a l s may be output
t o the baseband processing c i r c u i t p a r t 22.
[0042]
In t h e l a t t e r case, f o r example, t h e R F r e c e i v i n g c i r c u i t
p a r t 21 may have the following configuration. That is, a
~ predetermined o s c i l l a t i o n signal i s d i v i d e d o r m u l t i p l i e d , and
thereby, an o s c i l l a t i o n s i g n a l f o r RF s i g n a l m u l t i p l i c a t i o n
is generated. Then, t h e RF signal output from the s a t e l l i t e
receiving antenna 10 is m u l t i p l i e d by t h e generated o s c i l l a t i o n
signal, and thereby, t h e RF s i g n a l is down-converted t o an
intermediate frequency s i g n a l ( h e r e i n a f t e r , I F s i g n a l ) , the
I F s i g n a l is amplified, and then, converted i n t o a d i g i t a l
signal using the A/D converter and output t o the baseband
processing c i r c u i t p a r t 22.
[0043]
T h e b a s e b a n d p r o c e s s i n g c i r c u i t p a r t 2 2 performs c a r r i e r
removal, c o r r e l a t i o n processing, o r t h e l i k e on the s i g n a l
received i n the RF receiving c i r c u i t p a r t 2 1 and captures the
GPS s a t e l l i t e s i g n a l s and the quasi-zenith s a t e l l i t e s i g n a l s .
Then, the p a r t performs predetermined p o s i t i o n c a l c u l a t i o n
based on the ephemerides e x t r a c t e d from the captured GPS
s a t e l l i t e s i g n a l s and the positioning support information
e x t r a c t e d from the captured quasi-zenith s a t e l l i t e s i g n a l s ,
and c a l c u l a t e s the p o s i t i o n ( p o s i t i o n coordinates) of t h e
p o s i t i o n c a l c u l a t i o n apparatus 1 and the clock e r r o r s .
[0044]
The h o s t processing u n i t 30 is r e a l i z e d b y a c a l c u l a t i o n
device including a CPU, f o r example, and generally c o n t r o l s
t h e respective u n i t s of t h e p o s i t i o n c a l c u l a t i o n apparatus 1
accordingtovariousprogramsincludingasystemprogramstored
inthememoryunit35. For example, t h e u n i t a l l o w s t h e d i s p l a y
u n i t 32 t o d i s p l a y a map on which the current l o c a t i o n is
i n d i c a t e d based on t h e p o s i t i o n coordinates acquired f r o m t h e
baseband processing c i r c u i t p a r t 22, or uses the p o s i t i o n
coordinates f o r various kinds of a p p l i c a t i o n processing.
[0045]
T h e o p e r a t i o n u n i t 3 1 i s aninputdeviceincludingatouch
panel and a b u t t o n switch, and outputs an operation s i g n a l i n
response t o t h e operation t o the host processing u n i t 30.
By the operation of t h e operation u n i t 31, various kinds
of i n s t r u c t i o n i n p u t i n c l u d i n g a p o s i t i o n c a l c u l a t i o n request
is made.
[0046]
The display unit 32 is a display device including anLCD,
for example, and performs various kinds of display based on
display signals input from the host processing unit 30. The
sound output unit 33 is a sound output device including a
speaker, for example, and performs various kinds of sound
output based on sound signals input fromthe host processing
unit 30. The clock unit 34 is an internal clock and includes
an oscillator circuit such as a crystal oscillator.
[0047]
The memory unit 35 is realized by a memory device
including a ROM and a RAM, for example, and stores a system
program for general control of the position calculation
apparatusl, variousprogramsanddata for executionof various
kinds of application processing etc.
[0048]
Fig. 2 is a functional configuration diagram of the
baseband processing circuit part 22. The baseband processing
circuit part 22 includes a processing part 100 and a memory
part 200.
[0049]
The processing part 100 is realized by a calculation
device including a CPU and a DSP, for example, and performs
overall control of the baseband processing circuit part 22
based on the programs, data, etc. stored in the memory part
200. Further, the processing part 100 has a GPS- satellite
capturing p a r t 1 1 0 , a quasi-zenith s a t e l l i t e capturing p a r t
1 2 0 , a coordinate transformation matrix generation p a r t 130,
a f t e r t h e p o w e r i s t u r n e d o n andthe l a t e s t c a l c u l a t e d p o s i t i o n
a t t h e second and subsequent p o s i t i o n c a l c u l a t i o n .
[0051]
Then, t h e p a r t captures the GPS s a t e l l i t e s i g n a l s with
respect t o each s a t e l l i t e t o be captured. That i s , t h e p a r t
performs c o r r e l a t i o n c a l c u l a t i o n on t h e reception s i g n a l s
I
output from the RF receiving c i r c u i t p a r t 21 using r e p l i c a C/A
codes corresponding t o t h e s a t e l l i t e s t o be captured, and
thereby, captures the s a t e l l i t e s t o be captured. Then, the
p a r t removes c a r r i e r with respect t o t h e capturedGPS s a t e l l i t e
s i g n a l s , decodes navigation messages contained i n t h e GPS
an ephemeris estimation p a r t 140, a p o s i t i o n c a l c u l a t i o n p a r t
150.
[0050]
The GPS s a t e l l i t e capturing p a r t 110 captures the GPS
s a t e l l i t e s i g n a l s . F i r s t , the p a r t s e l e c t s GPS s a t e l l i t e s
( s a t e l l i t e s t o be captured) as t a r g e t s of capturing.
S p e c i f i c a l l y , a t the current time timed i n the clock u n i t 34,
the p a r t determines GPS s a t e l l i t e s l o c a t e d i n t h e s k y i n a given
reference p o s i t i o n using an almanac, long-term p r e d i c t i o n
o r b i t data, e t c . acquired i n advance as the s a t e l l i t e s t o be
captured. For example, t h e reference p o s i t i o n is a p o s i t i o n
acquired by server a s s i s t a t the f i r s t p o s i t i o n c a l c u l a t i o n
satellite signals, and acquires ephemerides contained in the
navigation messages. The acquired ephemerides are stored in
the memory part 200 as received ephemeris information 232 of
the GPS satellites.
[0052]
The quasi-zenith satellite capturing part 120 captures
the quasi-zenith satellite signals. That is, like the
capturing ofthe GPS satellites by the GPS satellite capturing
part 110, the part performs correlation calculation on the
reception signals output from the RF receiving circuit part
21 using replica C/A codes corresponding to the quasi-zenith
sa'tellite to be captured, and thereby, captures the
quasi-zenith satellite. Then, the part removes carrier with
respect to the captured quasi-zenith satellite signals and
decodes the positioning support information contained in the
quasi-zenith satellite signals. The acquired positioning
support information is stored as positioning support
information 220 in the memory part 200.
[0053]
Thecoordinatetransformationmatrixgenerationpart130
calculates a coordinate transformation matrix Q between the
earth centered inertial (ECI) coordinate system and the earth
centered earth fixed (ECEF) coordinate system defined by the
formulae (4) using the earth orientation parameters (EOP)
contained in the positioning support information 220.
[0054].
The ephemeris estimation part 1 4 0 estimates ' t h e
ephemerides of the respective GPS s a t e l l i t e s 3 based on t h e
p o s i t i o n i n g support information 220. S p e c i f i c a l l y , the p a r t
transforms the p o s i t i o n r O and the v e l o c i t y vO of t h e GPS
s a t e l l i t e containedinthepositioning support information 220
from t h e e a r t h centered e a r t h fixed (ECEF) coordinate system
t o t h e e a r t h centered i n e r t i a l ( E C I ) coordinate system using
the coordinate transformation matrix Q generated by the
coordinate transformation matrix generation p a r t 130. Then,
the p a r t performs numeric i n t e g r a t i o n on t h e o r b i t a l function
r ( t ) of the formula (3) with the p o s i t i o n r O and the v e l o c i t y
vO a f t e r coordinate transformation as i n i t i a l values, and
thereby, obtains t h e o r b i t a l function r ( t ) expressing t h e
s a t e l l i t e o r b i t . Then, the p a r t c a l c u l a t e s an ephemeris
adapted t o the s a t e l l i t e o r b i t expressed by the o r b i t a l
function r ( t ) . For example, t h e c a l c u l a t i o n of the ephemeris
may be obtained by numerical c a l c u l a t i o n ( e . g., l e a s t square
method) t h a t minimizes the d i f f e r e n c e between t h e s a t e l l i t e
o r b i t b a s e d o n t h e p a r a m e t e r v a l u e s oftheprescribedephemeris
a n d t h e s a t e l l i t e o r b i t e x p r e s s e d b y t h e o r b i t a l f u n c t i o n r ( t ) .
Obviously, theothermethodsmaybeused. Then, t h e c a l c u l a t e d
ephemeris is s t o r e d as estimated ephemeris information 233 of
the corresponding GPS s a t e l l i t e i n the memory p a r t . 200.
[0055]
The position calculation part 150 calculates the
position of the position calculation apparatus 1.
Specifically, after the power is turned on, the part performs
position calculation using the estimated ephemeris
information 233 of the respective GPS satellites 3 to be
capturedasthefirstpositioncalculation. Subsequently, the
GPS satellite signals are continuously received fromthe GPS
satellites 3 and the acquisition of the ephemerides of the
respective GPS satellite signals to be captured is completed,
and the part performs position calculation usingthe received
ephemeris information 232. The calculated positions are
accumulated and stored as calculated position data 240 in
correspondence with the calculation times, for example, in the
memory unit 35.
[0056]
The memory part 200 is realized by a memory device
including a ROM and a RAM, for.example, and stores a.system
program for general control ofthe basebandprocessing circuit
part 22 using the processing part 100, programs and data for
realizing various kinds of functions etc. and is used as a work
area of the processing part 100 in which calculation results
by the execution of the processing part 100 according to the
various programs are temporarily stored. In the embodiment,
a baseband processing program 210, the positioning support
information220, individualsatelliteinformation230, andthe
! calculated p o s i t i o n data 240 are s t o r e d .
[0057]
The i n d i v i d u a l s a t e l l i t e information 230 is generated
with respect t o each GPS s a t e l l i t e 3, and includes a s a t e l l i t e
I D 231 f o r i d e n t i f i c a t i o n of the corresponding GPS s a t e l l i t e
3, the received ephemeris information 232, the estimated
ephemeris information 233, and measurement information 234.
[0058]
I i [Flow of Processing]
Fig. 3 i s a f l o w c h a r t f o r e x p l a n a t i o n o f a f l o w o f b a s e b a n d
processing. T h e p r o c e s s i n g i s realizedbytheprocessingpart
100 executing the baseband processing program 2 1 0 .
[0059]
F i r s t , t h e quasi-zenith s a t e l l i t e capturing p a r t 120
captures the quasi-zenith s a t e l l i t e s i g n a l and acquires the
p o s i t i o n i n g support information contained i n the captured
quasi-zenith s a t e l l i t e s i g n a l ( s t e p A 1 ) . Then, t h e coordinate
transformation matrix generation p a r t 130 generates the
coordinate t r a n s f o r m a t i o n m a t r i x Q between the e a r t h centered
i n e r t i a l ( E C I ) coordinate system and t h e e a r t h centered e a r t h
fixed (ECEF) coordinate system using t h e acquired e a r t h
orientationparameters (EOP) ( s t e p A 3 ) . Subsequently, theGPS
s a t e l l i t e capturing p a r t 110 s e l e c t s t h e GPS s a t e l l i t e s t o be
captured ( s t e p A5).
Then, the ephemeris estimation part 140 performs orbit
estimation processing on the respective selected satellites
tobe capturedinparallel. Inthe orbitestimationprocessing,
first, the position rO andthevelocityv0 ofthe corresponding
GPS satellite contained in the acquired capture support
information is coordinate-transformed using the coordinate
transformation matrix Q (step A7). Then, the equation of
motion with respect to the GPS satellite is generated (step
A9), the equation of motion is numerically integrated with the
position rO and the velocity vO after the coordinate
transformation as initial values, and thereby, a predicted
satellite orbit of the GPS satellite is calculated (step All).
Then, an estimated ephemeris is calculated from the predicted
satellite orbit (step A13).
[0061]
If the calculation of the estimated ephemeris is
completed with respect to all satellites to be captured (step
A15: YES), position calculation using the estimated
ephemerides is performed and the position of the position
calculation apparatus 1 is calculated (step A17).
Specifically, the positions of the GPS satellites 3 to be
captured are specified using the estimated ephemerides, and
the current position of the position calculation apparatus 1
is calculated from the satellite positions and the pseudo
ranges basedon the received GPS satellite signals. Then, the
calculated position is output for display on the display unit
32, for example (step A19).
[0062]
Subsequently, capturing processing on the respective
satellites to be captured is performed in parallel. In the
capturingprocessing, the corresponding GPS satellite signals
are captured (step A21). Then, the measurement information
(code phases and reception frequencies) of the captured GPS
satellites are acquired (step A23), and then, decoding of the
navigation messages is performed (step A25).
[0063]
If the acquisition of the navigation messages is
completed with respect to the satellites to be captured (step
A27: YES), position calculation using the ephemerides
contained in the acquired navigation messages is performed,
a n d t h e r e b y , t h e p o s i t i o n o f t h e p o s i t i o n c a l c u l a t i o n a p p a r a t u s
1 is calculated (step A29). On the other hand, if the
acquisition of the navigation messages is not completed (step
A27: NO), positioncalculationusingtheestimatedephemerides
is performed (step A31). Then, the calculated position is
output for display on the display unit 32, for example (step
A33).
[0064]
Then, the processing part 100 determines whether or not
to end the processing. If the part does not end the processing
( s t e p A35: N O ) , the p a r t r e t u r n s t o s t e p A21. I f t h e p a r t ends
the processing ( s t e p A35: YES), t h e p a r t ends t h e baseband
processing.
[0065]
[Advantages]
As described above, the p o s i t i o n c a l c u l a t i o n apparatus
1 of t h e embodiment receives t h e p o s i t i o n i n g support
information superimposedon the quasi-zenith s a t e l l i t e s i g n a l
t r a n s m i t t e d by t h e quasi-zenith s a t e l l i t e 5 a t t h e f i r s t
p o s i t i o n c a l c u l a t i o n without ephemerides, p r e d i c t s t h e
s a t e l l i t e o r b i t s o f t h e GPS s a t e l l i t e s 3 b a s e d o n t h e p o s i t i o n s
and v e l o c i t i e s of t h e GPS s a t e l l i t e s 3 contained i n t h e
p o s i t i o n i n g support information, and performs p o s i t i o n
c a l c u l a t i o n u s i n g t h e ephemerides estimatedfromthepredicted
s a t e l l i t e o r b i t s . Thereby, thepositioncalculationusingthe
p o s i t i o n i n g support information received from t h e
quasi-zenith s a t e l l i t e 5 may be performed without waiting f o r
the a c q u i s i t i o n of t h e ephemerides from the GPS s a t e l l i t e
s i g n a l s t r a n s m i t t e d b y t h e GPS s a t e l l i t e s 3, a n d t h u s , t h e time
t o f i r s t f i x (TTFF) may be reduced.
[0066]
[Modified Examples]
The embodiments t o w h i c h t h e ' i n v e n t i o n i s a p p l i c a b l e are
not l i m i t e d t o the above described embodiment and, obviously,
changes may be a p p r o p r i a t e l y made without departing from t h e
scope of t h e invention.
LO0671
(A) Position Calculation of GPS S a t e l l i t e s
In t h e above described embodiment, the s a t e l l i t e o r b i t s
( o r b i t a l functions r ( t ) ) of the GPS s a t e l l i t e s a r e obtained
from the p o s i t i o n i n g support information and the ephemerides
r e p r e s e n t i n g t h e s a t e l l i t e o r b i t s are estimated. However, the
p o s i t i o n s o f t h e GPS s a t e l l i t e s 3 maybe d i r e c t l y obtained from
the s a t e l l i t e o r b i t s ( o r b i t a l functions r (t)) and the p o s i t i o n
c a l c u l a t i o n may be performed using the s a t e l l i t e p o s i t i o n s .
[0068]
S p e c i f i c a l l y , as shown i n Fig. 4, regarding the
s a t e l l i t e s t o b e captured, whenthepredictedsatellite o r b i t s
( i - e . , the o r b i t a l functions r ( t ) expressing the s a t e l l i t e
o r b i t s ) a r e c a l c u l a t e d ( s t e p A l l ) , the p o s i t i o n s of the GPS
s a t e l l i t e s a t a given time t are c a l c u l a t e d from the predicted
o r b i t s ( s t e p B13). I f t h e s a t e l l i t e p o s i t i o n is c a l c u l a t e d
with respect t o a l l s a t e l l i t e s t o be captured ( s t e p B15: YES),
p o s i t i o n c a l c u l a t i o n using the s a t e l l i t e p o s i t i o n s i s
performed, and thereby, t h e p o s i t i o n of the p o s i t i o n
c a l c u l a t i o n apparatus l a t t h e given t i m e t i s c a l c u l a t e d ( s t e p
B 1 7 ) . Then, the c a l c u l a t e d p o s i t i o n is output f o r d i s p l a y on
the d i s p l a y u n i t 32, f o r example ( s t e p B19). Then, the
processing p a r t 100 determines whether or not t o end the
processing. I f the p a r t doesnot endthe processing (stepA35:
NO), the part returns to step B13. If the part ends the
processing (step A35: YES), the part ends the baseband
processing.
[0069]
According to the modified example, it is not necessary
to calculate the estimated ephemerides from the predicted
orbits or continuously receive the GPS satellite signals to
acquire the ephemerides.
[0070]
(B) Positioning Support Information
Further, in the above described embodiment, the example
in which the positioning support information contains a single
piece of position information and a single piece of velocity
information of the position rO and the velocity vO at a certain
time tO is explained, however, the information may contain
position information and velocity information at a plurality
of times.
[0071]
(C) Satellite Positioning System
Furthermore, in the above described embodiment, the
example of the position calculation apparatus that acquires
the ephemerides of the GPS satellites to perform position
calculation is explained, however, the other satellite
positioning systems including WAAS (Wide Area Augmentation
System), GLONASS (GLObal Navigation Satellite System), and
GALILEO may be employed.
[0072]
(D) Artificial Satellite
In addition, in the above described embodiment, the
artificial satellite is the quasi-zenith satellite, however,
the satellite may be a geostationary satellite. When the area
where the position calculation apparatus 1 is used is an area
near the equator, the geostationary satellite is preferable.
Further, though the reception range is limited, obviously, an
apparatus on the earth (ground) may be substituted for the
satellite. For example, as shown in Fig. 5, a ground
communication device 6 including an IMES (Indoor MEssaging
System), a server device internally or externally having a
transmission function, and a base station for cell phone and
data communications may be employed. In this case, it is
preferable that the ground communication device 6 may be
adaptedtoperformtransmissioninthe sametransmission system
as that of the above described artificial satellite
(transmission protocol, transmission frequency, modulation
system, or the like). If the transmission is performed in
different transmission system, it is necessary that the
position calculation apparatus 1 has a receiving function
compliant to the transmission system.
Reference Signs List
[0073]
1 position calculation apparatus, 3 GPS satellite, 5
quasi-zenith satellite, 10 satellite receiving antenna, 20
satellite signal receiving unit, 30 host processing unit, 31
operation unit, 32 display unit, 33 sound output unit, 34 clock
unit, 35 memory unit.
WE CLAIM
[Claim 11
A position calculation method comprising:
receivingpositioning support information containing at
least information of aposition and avelocityof apositioning
satellite from an artificial satellite that transmits the
positioning support information;
calculating orbital information of the positioning
sat,ellite using the positioning support information; and
calculating a position of a receiver using a signal from
the positioning satellite and the orbital information.
[Claim 21
A position calculation method comprising:
receivingpositioning support information containing at
least information of a position and avelocity of apositioning
satellite from a ground communication device that transmits
the positioning support information;
calculating orbital information of the positioning
satellite using the positioning support information; and
calculating a position'of a receiver using a signal from
the positioning satellite and the orbital information.
[Claim 31
The position calculation method according to claim 1 or
2, wherein the information of the position and the velocity
of the positioning satellite contained in the positioning
support information is information of the position and the
velocity of the positioning satellite at a given time.
[Claim 41
The position calculation method according to any one of
claims 1 to 3, wherein the calculating the orbital information
includes calculatingthe orbitalinformationusinganequation
of motion expressing motion of a satellite orbiting the earth
and the position and the velocity ofthe positioning satellite
contained the positioning support information.
[Claim 51
The position calculation method according to claims 4,
wherein the positioning support information further contains
earth orientation information,
the equation of motion is defined by an inertial
coordinate system with reference to the earth center,
the position and the velocity contained in the
positioning support information are defined by a fixed
coordinate system with reference to the earth center, and
the calculating the orbital information includes
coordinate-transforming the position and the velocity
contained i n the p o s i t i o n i n g support information i n t o a
positionandavelocityoftheinertialcoordinate systemusing
t h e e a r t h o r i e n t a t i o n i n f o r m a t i o n containedinthepositioning
support information.
[Claim 61
The p o s i t i o n c a l c u l a t i o n method according t o any one of
claims 1 t o 5, wherein the c a l c u l a t i n g the o r b i t a l information
i n c l u d e s o b t a i n i n g a parameter of an ephemeris of t h e
p o s i t i o n i n g s a t e l l i t e .
[Claim 71
A p o s i t i o n c a l c u l a t i o n method comprising:
r e c e i v i n g p o s i t i o n i n g support informationcontaining a t
l e a s t information of a p o s i t i o n a n d a v e l o c i t y o f a p o s i t i o n i n g
s a t e l l i t e from an a r t i f i c i a l s a t e l l i t e t h a t t r a n s m i t s t h e
p o s i t i o n i n g support information;
obtaining ' an o r b i t a l function of the p o s i t i o n i n g
s a t e l l i t e using an equation of motion expressing motion of a
s a t e l l i t e o r b i t i n g the e a r t h and t h e p o s i t i o n a n d t h e v e l o c i t y
of the p o s i t i o n i n g s a t e l l i t e contained i n the p o s i t i o n i n g
support information;
e s t i m a t i n g a s a t e l l i t e p o s i t i o n of t h e p o s i t i o n i n g
s a t e l l i t e using the o r b i t a l function; and
c a l c u l a t i n g a p o s i t i o n of a r e c e i v e r using a s i g n a l from
the positioning satellite andthe estimated satellite position
of the positioning satellite.
[Claim 81
A position calculation method comprising:
receivingpositioning support information containing at
least information of aposition and avelocity of apositioning
satellite from a ground communication device that transmits
the positioning support information;
I obtaining an orbital function of the positioning
I
I satellite using an equation of motion expressing motion of a
I satellite orbiting the earth and the position and the velocity
of the positioning satellite contained in I the positioning
support information;
estimating a satellite position of the positioning
satellite using the orbital function; and
calculating a position of a receiver using a signal from
the positioning satellite andthe estimatedsatelliteposition
of the positioning satellite.
[Claim 91
A position calculation apparatus comprising:
a receiving unit that receives positioning support
information containing at least information of a position and
a velocity of a positioning satellite from an artificial
satellite that transmits the positioning support information;
an orbital information calculation unit that calculates
orbital information of the positioning satellite using the
positioning support information; and
a position calculation unit that calculates a position
using a signal from the positioning satellite and the orbital
information.
[Claim 101
A position calculation apparatus comprising:
a receiving unit that receives positioning support
information containing at least information of a position and
1 a velocity of a positioning satellite from a ground
communication device that transmits the positioning support
information;
an orbital information calculation unit that calculates
orbital information of the. positioning satellite using the
positioning support information; and
a position calculation unit that calculates a position
I
using a signal from the positioning satellite and the orbital
- information.