# US 7,741,994 B2 · Ionospheric error prediction and correction in satellite positioning systems

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- Number: US 7,741,994 B2
- Document ID: US7741994B2
- Status: Granted
- Kind: B2
- Application number: 10/504,233
- Filed: 2003-02-13
- Published: 2005-07-07
- Granted: 2010-06-22
- Earliest claimed: 2002-02-13
- Assignees: SiRF Technology, Inc.
- Inventors: Ashutosh Pande; Junichi Suzuki
- Web page: https://patentgrep.com/patent/US7741994B2

## CPC

- G01S 19/072: {Ionosphere corrections}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

A GPS server capable of receiving information for use in determining ionospheric errors using mathematical formulas and sending ionospheric error correction information to GPS receivers that are in a location capable of receiving the ionospheric error correction information.

## Claims

### Claim 1

A method for correcting ionospheric errors in a satellite positioning system (“SPS”) having a SPS server with known positional coordinates and a mobile SPS receiver, the method comprising:
receiving SPS signals from SPS satellites at the SPS server;
calculating a position of the SPS server using the SPS signals from the SPS satellites;
comparing calculated positional coordinates of the calculated position of the SPS server with the known positional coordinates;
determining ionospheric errors in response to comparing the calculated positional coordinates of the calculated position of the SPS server with the known positional coordinates;
creating an ionospheric model of predicted ionospheric errors from the determined ionospheric errors, the ionospheric model having ionospheric model parameters; and
transmitting the ionospheric model parameters to the mobile SPS receiver, where the mobile SPS receiver uses the ionospheric model parameters to create an SPS receiver ionospheric model.

### Claim 2 (depends on 1)

The method of claim 1, wherein creating an ionospheric model includes utilizing a half cosine curve.

### Claim 3 (depends on 1)

The method of claim 1, wherein creating an ionospheric model includes utilizing a triangle shape curve.

### Claim 4 (depends on 1)

The method of claim 1, wherein creating an ionospheric model includes utilizing a lookup table.

### Claim 5 (depends on 1)

The method of claim 1, further including:
receiving new SPS signals at the SPS server;
determining new ionospheric errors in response to receiving the new SPS signals;
comparing the new determined ionospheric errors to the predicted ionospheric error from the ionospheric model;
adjusting the ionospheric model of predicted ionospheric errors in response to the comparison outside a predetermined threshold value, the adjusted ionospheric model having adjusted the ionospheric model parameters; and
transmitting the adjusted ionospheric model parameters to the mobile SPS receiver.

### Claim 6 (depends on 5)

The method of claim 5, wherein the predetermined threshold value corresponds to the changing points of the ionospheric model.

### Claim 7 (depends on 6)

The method of claim 6, wherein creating an ionospheric model includes utilizing a half cosine curve.

### Claim 8 (depends on 6)

The method of claim 6, wherein creating an ionospheric model includes utilizing a triangle shape curve.

### Claim 9 (depends on 6)

The method of claim 6, wherein creating an ionospheric model includes utilizing a lookup table.

### Claim 10 (depends on 5)

The method of claim 5, further including:
receiving the new SPS signals at the mobile SPS receiver;
receiving the transmitted ionospheric model parameters from the SPS server;
creating, at the SPS receiver, a mobile SPS receiver ionospheric model of predicted ionospheric errors from the received ionospheric model parameters;
determining the calculated positional coordinates with the mobile SPS receiver ionospheric model.

### Claim 11 (depends on 10)

The method of claim 10, wherein creating an ionospheric model includes utilizing a half cosine curve.

### Claim 12 (depends on 10)

The method of claim 10, wherein creating an ionospheric model includes utilizing a triangle shape curve.

### Claim 13 (depends on 10)

The method of claim 10, wherein creating an ionospheric model includes utilizing a lookup table.

### Claim 14

A satellite positioning system (“SPS”) comprising:
a SPS server configured to detect ionospheric errors in received SPS signals from SPS satellites, to create an ionospheric error model of predicted ionospheric errors, to determine ionospheric model parameters from the ionospheric error model, and to transmit the ionospheric model parameters via a communication link;
a mobile SPS receiver in signal communication with the SPS server via the communication link, the mobile SPS receiver configured to receive both the received SPS signals from the SPS satellites and the ionospheric model parameters transmitted from the SPS server and, in response to receiving both the received SPS signals and ionospheric model parameters the mobile SPS receiver is capable of creating the ionospheric error model using the ionospheric model parameters to compensate for the ionospheric errors in the received SPS signals.

### Claim 15 (depends on 14)

The SPS of claim 14, wherein the SPS server further includes:
a server position calculation module in the SPS server;
a server ionospheric error modeling module in signal communication with the SPS receiver; and
a server processor in signal communication with the server position calculation module, server ionospheric error modeling module and server communication module, the processor capable of creating the ionospheric error model.

### Claim 16 (depends on 14)

The SPS of claim 14, further including a server storage module in signal communication with the server position calculation module, server ionospheric error modeling module, server processor and server communication module.

### Claim 17 (depends on 16)

The SPS of claim 16, wherein the SPS server is capable of receiving and processing both L1 and L2 carrier frequencies.

### Claim 18 (depends on 14)

The SPS of claim 14, wherein the mobile SPS receiver further includes:
a mobile position calculation module in the mobile SPS receiver;
a mobile ionospheric error modeling module in signal communication with the mobile position calculation module; and
a mobile processor in signal communication with both the server position calculation module and server ionospheric error modeling module, the processor capable of compensating for ionospheric errors in the received SPS signals utilizing ionospheric model parameters.

### Claim 19 (depends on 18)

The SPS of claim 18, further including a mobile storage module in signal communication with the mobile position calculation module, mobile ionospheric error modeling module, mobile processor and mobile communication module.

### Claim 20

A satellite positioning system (“SPS”) comprising:
means for detecting ionospheric errors in received SPS signals transmitted from SPS satellites at a SPS server;
means for creating an ionospheric error model of predicted ionospheric errors and determining ionospheric error model parameters from the ionospheric error model in response to detecting the ionospheric errors with the detecting means; and
a mobile SPS receiver in signal communication with the detecting means and creating means via a communication link, the mobile SPS receiver capable of receiving both the received SPS signals and the ionospheric model parameters, the mobile SPS receiver is capable of creating the ionospheric error model using the ionospheric model parameters to compensate for ionospheric errors in the receiver SPS signals.

### Claim 21 (depends on 20)

The SPS of claim 20, wherein the SPS server further includes:
means for calculating the position of the SPS server from the received SPS signals;
means for modeling the ionospheric error from the received SPS signals;
means for communicating to the mobile SPS receiver; and
means for controlling the calculating means, modeling means and communication means.

### Claim 22

The SPS claim of 20, wherein the mobile SPS receiver further includes:
means for calculating the position of the mobile SPS receiver;
means for communicating to the SPS server; and
means for modeling the ionospheric error from the received SPS signals at the SPS server.

### Claim 23

A computer-readable storage medium having instructions encoded thereon executable by a computer, the instructions when executed on a computer perform the steps of:
correcting ionospheric errors in an satellite positioning system (“SPS”) having a SPS server with known positional coordinates and a SPS receiver,
receiving SPS signals at the SPS server;
creating an ionospheric model of predicted ionospheric errors from the determined ionospheric errors, the ionospheric model having ionospheric model parameters; and
transmitting the ionospheric model parameters to the SPS receiver.

### Claim 24 (depends on 23)

The computer-readable storage medium of claim 23, further including the steps of:
determining calculated positional coordinates of the SPS server from the received SPS signals;
comparing the calculated positional coordinates of the SPS server to the known positional coordinates; and
determining the ionospheric error in response to comparing the calculated positional coordinates to the known positional coordinates.

### Claim 25 (depends on 24)

The computer-readable storage storage medium of claim 24, wherein the ionospheric model includes a half cosine curve.

### Claim 26 (depends on 24)

The computer-readable storage medium of claim 24, wherein the ionospheric model includes utilizing a triangle shape curve.

### Claim 27 (depends on 24)

The computer-readable storage medium of claim 24, wherein the ionospheric model includes a lookup table.

### Claim 28 (depends on 23)

The computer-readable storage medium of claim 23, further including the steps of:
receiving new SPS signals at the SPS server;
determining new ionospheric errors in response to receiving the new SPS signals;
comparing the new determined ionospheric errors to the predicted ionospheric error from the ionospheric model;
adjusting the ionospheric model of predicted ionospheric errors in response to the comparison outside a predetermined threshold value, the adjusted ionospheric model having adjusted ionospheric model parameters and
transmitting the adjusted ionospheric model parameters of the SPS receiver.