Ambiguity windowing in communications among global navigation system satellite receivers
A method of communicating corrections for information related to satellite signals among global navigation satellite system (GNSS) receivers is described. The method includes at a first GNSS device determining a component of position of a satellite. The component is then divided by a first value to thereby obtain an integer value and a remainder value, and the only the remainder value is transmitted from the first GNSS device to the second GNSS device. Knowing the first value, the second GNSS device calculates the component of position.
1. A method of communicating satellite observable information from a global navigation satellite system (GNSS), the method comprising:
at a first GNSS device, determining a first value of a satellite observable for a satellite;
at the first GNSS device, dividing the first value by a window size to obtain a first quotient and a first remainder value, wherein the window size is dynamically determined by the first GNSS device according to an estimated error of the first value; and
transmitting the first remainder value and data indicative of the window size from the first GNSS device to a second GNSS device without transmitting the first quotient;
at the second GNSS device, determining a second value of the satellite observable for the satellite;
at the second GNSS device, dividing the second value by the window size to obtain a second quotient and a second remainder value; and
at the second GNSS device, multiplying the second quotient by the window size and adding the first remainder value received from the first GNSS device to obtain the first value determined by the first GNSS device.
2. A method as in claim 1 wherein the first value and the second value comprise orbit data from the satellite.
3. A method as in claim 1 wherein the first value and the second value comprise position data of the satellite.
4. A method as in claim 1 wherein the first value and the second value comprise clock data from the satellite.
5. A method as in claim 1 wherein the first value and the second value comprise carrier phase data.
6. A method as in claim 1 wherein the first value and the second value comprise code phase data.
7. A method as in claim 1 further comprising, at the second GNSS device prior to dividing the second value by the window size, determining the window size according to the data indicative of the window size using a look-up table.
8. A method as in claim 1 further comprising, at the first GNSS device prior to dividing the first value by the window size, removing data relating to at least one of ionospheric correction or tropospheric correction from the first value.
9. A method as in claim 1 wherein the first remainder value and the data indicative of the window size are included in a message, and the message also includes:
a first bit indicative of whether satellite position data is present in the message;
a second bit indicative of whether satellite clock data is present in the message; and
wherein the data indicative of the window size comprises a first set of bits defining the window size.
10. A method as in claim 9 wherein the message also includes a second set of bits defining a precision for the first value.
11. A method of communicating satellite observable information from a global navigation satellite system (GNSS), the method comprising, at a rover receiver:
receiving a first remainder value and data indicative of a window size from a reference receiver, wherein the first remainder value is obtained by the reference receiver by dividing a first value of a satellite observable for a satellite by the window size, the first value determined by the reference receiver;
determining a second value of the satellite observable for the satellite;
dividing the second value by the window size to obtain a quotient and a second remainder value; and
multiplying the quotient by the window size and adding the first remainder value to obtain the first value determined by the reference receiver.
12. A method as in claim 11 wherein the first value and the second value comprise orbit data from the satellite.
13. A method as in claim 11 wherein the first value and the second value comprise position data of the satellite.
14. A method as in claim 11 wherein the first value and the second value comprise clock data from the satellite.
15. A method as in claim 11 wherein the first value and the second value comprise carrier phase data.
16. A method as in claim 11 wherein the first value and the second value comprise code phase data.
17. A method as in claim 11 further comprising, prior to dividing the second value by the window size, determining the window size according to the data indicative of the window size using a look-up table.
18. A method as in claim 11 wherein data relating to at least one of ionospheric correction or tropospheric correction is removed from the first value prior to being divided by the window size.
19. A method as in claim 11 wherein the first remainder value and the data indicative of the window size are included in a message, and the message also includes:
a first bit indicative of whether satellite position data is present in the message;
a second bit indicative of whether satellite clock data is present in the message; and
wherein the data indicative of the window size comprises a first set of bits defining the window size.
20. A method as in claim 19 wherein the message also includes a second set of bits defining a precision for the first value.
21. A method as in claim 11 , wherein the window size is dynamically determined by the reference receiver according to an estimated error of the first value.