This subject invention generally relates to estimating the directions w.r.t magnetic North
using real time magnetometer data on mobile device.
10 BACKGROUND OF THE INVENTION
The present invention is related to Estimate directions using magnetometer and earth
magnetic field specifically for Aircraft, Helicopter and for any navigation system. The idea
for the same is taken from magnetic compass.
15 A magnetic compass capable of measuring the azimuth of a line of magnetic force
generated by an external magnetic field such as earth magnetism is widely used as a
means for detecting the position of a vehicle, such as Aircraft, Helicopter and a vehiclemounted
compass and a navigation system. A compass functions as a pointer to
"magnetic north" because the magnetized needle at its heart aligns itself with the lines of
20 the Earth's magnetic field.
Such a magnetic compass is a device capable of detecting magnetism in two directions
such as the X and Y directions orthogonal to each other on a plane using a magnetic
sensor such as a flux gate magnetometer and a Hall element. The horizontal component
of the earth magnetism is detected by sensors of the X and Y axes to thus calculate the
25 directions from the magnitude of the detected horizontal component.
The magnetometer obtains a measure of the magnetic field that is present in the
immediate surroundings of the mobile device as a two or three-component vector using
2-axis or 3-axis magnetic sensors. A calibration procedure is required because the
sensed magnetic field can contain a contribution of the Earth's magnetic field and a
30 contribution by a local interference field. The local interference field is created by
sources in the local environment of the mobile device. This may include contributions
made by one or more magnetic components that are near the magnetic sensors, such
as the magnet of a loudspeaker that is built into the mobile device. In most cases, the
interference field is not negligible relative to the Earth's magnetic field. Therefore, a
Annexure‐II
calibration procedure is needed to reduce the adverse impact of the interference field
contribution from the sensors' measurements to allow the magnetometer to calculate a
more accurate direction.
5
SUMMARY OF PRESENT INVENTION
In accordance with one aspect of present invention, the accuracy of Magnetometer
sensors should be high.
10 In accordance with second aspect of present invention, the magnetometer casing should
be Non-magnetic and no external magnetic field sources should be present near to the
magnetometer sensors.
In accordance with third aspect of present invention, the base of magnetometer casing
should be perfectly smooth.
15 In accordance with another aspect of present invention, the magnetometer should be
placed on the part of mobile device (Aircraft or Helicopter) where interference magnetic
field components is minimum.
In accordance with yet another aspect of present invention, magnetometer is capable to
transmit captured data through communication channel.
20
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention will become more apparent and
25 descriptive in the description when considered together with figures/flow charts
presented:
FIG. 1A illustrates an exemplary Cartesian coordinate system describing the Earth's
geomagnetic field in accordance with some implementations.
FIG. 1B illustrates an exemplary 2-axis magnetometer in accordance with some
30 implementations.
FIG. 2 is a block diagram of exemplary calibration system of magnetometer data and
capturing of data using work station in accordance with some implementations.
Annexure‐II
Fig. 3A showing top view of casing of magnetometer.
Fig. 3B showing side view of casing of magnetometer.
Fig. 4 showing earth’s magnetic field and its component in x-axis and y-axis.
5
DETAILED DESCRIPTION
FIG. 1 illustrates an exemplary Cartesian coordinate system for describing the Earth's
geomagnetic field in accordance with some implementations. The Earth's geomagnetic field
10 vector, {right arrow over (F)}, can be described by the orthogonal components X (northerly
intensity), Y (easterly intensity) and Z (vertical intensity, positive downwards); total intensity F;
horizontal intensity H; inclination (or dip) I, and declination (or magnetic variation) D.
Declination, inclination and total intensity can be computed from the orthogonal components
using the equations
15 D = arc tan ( Y/X ) ------------------------- (1)
I = arc tan ( Z/H ) -------------------------- (2)
F2=(H2+Z2)------------------------------------(3)
H=√{square root over (X2+Y2)} -------(4)
The International System of Units (SI) unit of magnetic field intensity most commonly used is the
20 Tesla.
FIG. 1B illustrates an exemplary 2-axis magnetometer in accordance with some
implementations. Magnetometers can be 2-axis or 3-axis and the processes described here
apply to both types of sensors. In the interest of brevity, only a 2-axis magnetometer is
described.
25 In some implementations, 2-axis magnetometer sensor configuration 100 can be used to
calculate a heading for a variety of applications, including applications running on a mobile
device. Sensor configuration 100 can include two magnetic field sensors 102, 104 mounted
orthogonally on a board, substrate or other mounting surface. Magnetic sensors 102, 104 can
be included in an integrated circuit (IC) package with or without other sensors, such as
30 accelerometers and gyros.
Annexure‐II
Sensor configuration 100 can be deployed in a host system environment that contains
interfering magnetic fields. Since the Earth's magnetic field is a weak field (~ 0.5 Gauss), nearby
magnetic objects can interfere with the accurate measurements of sensors 102, 104. A
calibration procedure can be deployed to isolate and remove the local magnetic interf5 erence.
Since Magnetometer sensors are very sensitive toward magnetic field they captures both the
earth’s magnetic field as well as interference (unwanted) magnetic field. The later one might be
greater or less than the earth’s magnetic field so the results would be different from expectation.
Unwanted magnetic field components can be minimise or remove by using Non-magnetic
10 casing material as shown in Fig. 3A and Fig. 3B and by calibration procedure.
Fig. 2 illustrates the Block diagram of how to prepare a set up to estimate directions. 201 is a
magnetometer that can capture the magnetic field (earth’s and unwanted magnetic field), 200 is
a Power supply to power up magnetometer which usually operated at 12 Volt. 202 is the
calibration system to calibrate magnetometer data or to remove the component of unwanted
15 magnetic field. 203 is communication channel that carries only earth’s magnetic field that is
communicated to work station to estimate direction with respect to magnetic North.
Mathematical calculations to estimate direction w.r.t magnetic North:The earth magnetic field’s
direction is constant i.e from magnetic south to magnetic north.
Suppose H is the magnetic field at any point on the earth, Hxy (400) is the xy-plane component
20 of the calibrated H, Hx (402) is the X component of Hxy (400) and also the x-axis of the
magnetometer, Hy (401) is the Y component of Hxy (400) and also the y-axis of the
magnetometer, Hz is the Z component of H. Angle ø (403) is the angle between xy-plane
component of H, which is constant, and Hx. Angle ø can be calculated as:
Angle ø = arc tan (Hy/Hx)
25 For magnetic north angle ø = 0 degree.
For magnetic south angle ø = 180 degree.

WE CLAIMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. We Claim

1. The said system, comprising:
- Metallic casing of system specifically used to house the complete arrangement for sensing magnetic related field and interfacing with outside systems via suitable interfaces. Further, the casing is useful in clamping the system with the vehicle of interest.
- Metallic screws used for tightening of atleast one component of the said system with casing.
- Interface ports for enabling communication to & fro wrt at least one type of data and atleast one type of power supply.
2. The said system as per claim 1, further comprises of a mobile generic computing device with display capability and atleast one interface port compatible with the system for exchange of atleast one type of data.
3. The said system as per claim 1, offers one of the lightest solution.
4. The system as per claim 1 & 2, capable of interfacing with each other such that atleast one type of data can be obtained from the said system either via command or without command.
5. The system as per claim 2, capable of interacting with the said system to cross verify health of the system as per claim 1, decoding it and displaying it for further analysis.
6. The system as per claim 1 & 2, capable of interfacing with each other without any distance limitation.
7. The system as per claim 1 & 2, capable to capture earth’s magnetic field components in 3-axis, estimate direction and display to the user in atleast one form say using dial arrangement.
8. The system as per claim 1 & 2, is capable of estimating atleast magnetic North.
9. The system as per claim 1 & 2, is capable of displaying atleast one result in real-time.
10. The system as per claim 1, wherein the said system is configured to withstand extreme operating environments including temperature (High & Low), altitude, vibration, pressure (Low & High), low temperature storage, humidity, rain, fungus, salt fog, dust, sand, functional shock, bench handling, gunfire vibration, EMI/EMC, Transit drop, Combined Altitude Temperature & Humidity (CATH), Dew & Icing, Linear Acceleration. ,TagSPECI:As per Annexure-II