Processing of satellite positioning system signals
The invention provides a method of processing signals from a satellite positioning system in which a user inputs an approximate indication of current position, and this is used when processing satellite samples to reduce the processing required or increase the reliability. This approach avoids the need for an automated approximate location system (for example using cellular telephony). This represents a change in the way GPS (or other satellite systems) is used. Instead of relying on a GPS system to provide a location in entirely automated manner, the approach is for the user to give an approximate location (which will generally be known), and for the GPS system then to correct this and provide an accurate location. This approach can enable the GPS system to function in areas where it would normally be unreliable.
1. A method of processing signals from a satellite positioning system, the method comprising:
receiving an indication of approximate location which has been provided directly by a user;
receiving data samples broadcast from the satellite positioning system at a location corresponding to the received indication;
processing the received data samples using the received indication of approximate location to derive a more accurate position than the approximate location.
2. The method as in claim 1 , wherein receiving the indication of approximate location comprises:
receiving a geographical place name or a landmark name; and deriving corresponding position information using a database.
3. The method as in claim 1 , wherein receiving the indication of approximate location comprises:
receiving a user-selected place name; and
deriving corresponding position information using a database.
4. The method as in claim 1 , further comprising:
deriving from the approximate location a range of possible position values for use in processing the received data samples.
5. The method as in claim 1 , wherein the received data samples comprise intermediate frequency downconverted data samples.
6. The method as in claim 1 , wherein the satellite broadcast data comprise Code Divison Multiple Access (CDMA) data.
7. The method as in claim 1 , further comprising:
converting the indication of approximate location into longitude and latitude ranges for use when processing the samples.
8. The method as claimed in claim 1 , further comprising:
requesting from an external service conversion of the indication of approximate location into longitude and latitude ranges for use when processing the samples; and
receiving the longitude and latitude ranges.
9. The method as in claim 1 , wherein the processing of samples takes place when and where the data samples are received.
10. The method as in claim 1 , further comprising:
storing the data samples, and wherein the processing of samples takes place subsequently and not necessarily where the samples are received.
11. The method as in claim 10 , further comprising:
storing the indication of approximate location with the data samples.
12. The method as in claim 10 , wherein the indication of approximate location is provided after storing the data samples, and at or before the time when processing the samples.
13. The method as in claim 1 , wherein receiving directly from a user an indication of approximate location comprises:
receiving a user input as keystrokes or selections using a graphical user input of a portable Global Positioning System (GPS) receiver device.
14. A method of operating a satellite positioning system, the method comprising:
entering, by a user, an approximate indication of current position;
receiving data samples broadcast from the satellite positioning system; and
processing the received samples using the approximate indication of current position to derive a more accurate position than the approximate indication.
15. A system for collecting data from a satellite positioning system, the system comprising:
a user interface adapted to receive from a user an indication of approximate location;
a satellite receiver for receiving data samples broadcast from the satellite positioning system; and
processing means for processing the received data samples using the indication of approximate location to derive a more accurate position than the approximate indication.
16. The method of claim 1 , further comprising:
receiving different levels of accuracy from the user.
17. The method of claim 1 , further comprising:
using the more accurate position to deduce a Doppler shift of signals from the satellite positioning system.
18. The method of claim 1 , wherein a server performs the processing step and sends the more accurate position to the user.
19. The method of claim 1 , further comprising:
detecting whether signal quality from the satellite positioning system is poor.
20. The method of claim 1 , further comprising:
after determining that signal quality is poor, requesting assistance from the user.