Just some info for you all
How CDMA GPS Works in Blackberry
Different modes of operation are chosen automatically or specified by software, In the A-GPS modes, gpsOne technology utilizes assistance data from a location server in the wireless network in combination with A-GPS circuitry and software in the wireless device.
Standalone (Autonomous) GPS: The GPS receiver calculates a position without using any assistance data and without a connection to the wireless network. Note:
Verizon does not support the Standalone mode. For BlackBerry Device Software 4.7 and later (ie 9530 Storm), Standalone mode is open to applications that are signed by RIM.
MS-Based: The GPS receiver calculates the position using assistance data from a location server to increase cold-start sensitivity and reduce the start time for an initial position calculation.
MS-Assisted: The GPS receiver uses assistance data from a location server to make measurements related to its distance from the GPS satellites, then sends this information to the location server where the position is calculated. This mode also increases cold start sensitivity and reduces the start time for an initial position calculation.Note:
Verizon requires third-party applications to have a valid Client ID and Password for access to their Location Proxy Server (LPS).
There are three more modes that use a combination of MS-Based and MS-Assisted to achieve a location fix.
MS-based position calculation is preferred Accuracy optimal
PDE-based fix/MS-assisted mode is done only if MS-based position calculation fix fails
Ephemeris download from PDE is preferred as compared with data demodulation
PDE-based position calculation/MS-assisted mode is a preferred option MS-based position calculation only if PDE-based fix failsEphemeris download from PDE is preferred as compared with data demodulationData optimal
Standalone mode is the preferred option and minimum PDE/network access is allowed
Data demodulation is preferred as compared with ephemeris download from PDE
MS-assisted position fix if MS-based position calculation fails to generate a fix
Data optimal mode disables SA download
Finally, another mode that simply returns the location of the cellular transmission site in contact with the BlackBerry smartphone is known as CellSite
. This mode is not part of Qualcomm gpsOne but is worth mentioning. Accuracy of this mode is obviously low: 400m to 2500m in urban areas and will vary by location. CellSite is recommended when accuracy is of least concern.
The different types of fixes are:
Cellsite: Which is the least accurate but the fastest location mode, uses cellsite towers that attempt to provide triangulated GPS information. Note:
Assisted: Which is more accurate than the Cellsite fix but not as fast, uses the network in an assisted search.
Autonomous (Standalone): Which yields the most accurate fix but provides the first fix the slowest, uses the on-board GPS chip.
All Qualcomm gpsOne modes, except Standalone and Cellsite, require a connection to a PDE server. To enable a connection to a PDE server, the IP address and the port of the server must be configured.
Resetting the LocationProvider
A LocationProvider may stop returning fixes when network coverage deteriorates or the BlackBerry is in an environment that is not suitable for receiving GPS data (for example, indoors). In these scenarios, the GPS chip will go completely cold to preserve battery power. If this event is triggered, an application can reset the provider to restore the GPS chip.
After a reset, the application can try to get a fix again; however, if the GPS chip fails to get a fix (if the network coverage or environment has not improved), it will again go cold and will stop getting fixes. It is strongly recommended not to reset the provider at an interval less than three minutes since it can take up to three minutes to get a fix from a cold start.
Keeping the GPS chip hot
The GPS chip is considered hot when it has an active connection with the satellites. A fix can be obtained almost instantly when the chip is hot. To preserve battery power, the chip is configured to go cold if the application does not ask for fixes for some time. From a cold start it may take much longer to get a fix. For applications that require frequent fixes, it is recommended that the application queries for fixes every 10 seconds.