Methods and systems for stationary user detection in a hybrid positioning system
This disclosure describes methods and systems for stationary user detection in a hybrid location system. In some embodiments, the method for determining whether a satellite enabled device is stationary by measuring the Doppler frequency of received satellite signals can include acquiring satellite measurements from at least two satellites, wherein the satellite measurements include Doppler frequency measurements, acquiring a rough estimate of location of the satellite enabled device and calculating an internal frequency offset of satellite enabled device.
1. A method for determining whether a satellite enabled device is stationary by measuring the Doppler frequency of received satellite signals comprising:
acquiring satellite measurements from two or three satellites, wherein the satellite measurements include Doppler frequency measurements;
acquiring a rough estimate of location of the satellite enabled device;
calculating an internal frequency offset of the satellite enabled device;
adjusting the Doppler frequency measurements to account for satellite movement and the internal frequency offset to provide a device Doppler frequency; and
determining that the device is stationary if the device Doppler frequency is small.
2. The method of claim 1 comprising determining that the device is stationary if the internal frequency offset for each satellite are substantially the same value.
3. The method of claim 1 , wherein a small Doppler frequency comprises a Doppler frequency corresponding to movement of the satellite enabled device of less than one mile per hour.
4. The method of claim 1 , further comprising if the device is determined to be stationary, implementing power saving features into a WLAN positioning system, located in the satellite enabled device.
5. The method of claim 4 , wherein power saving features comprise updating the device location less often by the WLAN positioning system.
6. The method of claim 5 , wherein updating the location of the devices less often comprises updating the location once a minute by the WLAN positioning system.
7. The method of claim 1 , wherein the rough estimate comprises an location estimate within about 2000 meters of the actual location of the device.
8. The method of claim 1 , wherein the rough estimate is provided by a WLAN positioning system.
9. A system for determining whether a satellite enabled device is stationary by measuring the Doppler frequency of received satellite signals comprising:
a positioning module comprising:
a satellite positioning module for obtaining satellite information from two or three different satellites, wherein the satellite measurements include Doppler frequency measurements;
logic located in the satellite positioning module for adjusting the Doppler frequency measurements to account for satellite movement and frequency offset of satellite enabled device to provide a device Doppler frequency and determining that the device is stationary if the device Doppler frequency is small.
10. The system of claim 9 , wherein the device is stationary if the internal frequency offset for each satellite are substantially the same value.
11. The system of claim 9 , wherein a small Doppler frequency comprises a Doppler frequency corresponding to movement of the satellite enabled device of less than one mile per hour.
12. The system of claim 9 , wherein if the device is determined to be stationary, power saving features are implemented into a WLAN positioning system located on the satellite enabled device.
13. The system of claim 12 , wherein power saving features comprise updating the device location less often by the WLAN positioning system.
14. The system of claim 13 , wherein updating the location of the devices less often comprises updating the location once a minute by the WLAN positioning system.