| Excerpt |
|---|
CommCare has several geospatial features that allow for calculating distances between geographic coordinates, sorting case lists by distance from you, and displaying case location data in a map view. |
| Table of Contents | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
GPS
CommCare supports a feature called Automatic GPS Capture to help you automatically capture GPS locations.
...
A cold start happens when the device was off for more than 4 hours and new ephemeris data needs to be downloaded. A warm start happens when the ephemeris data is still valid and the device simply needs to get a lock on satellites. A device is "hot" if it has that lock. To accelerate the "time to first fix" (time from turning on the device to getting coordinates), a variety of techniques get used: (http://en.wikipedia.org/wiki/Assisted_GPS).
A-GPS or assisted GPS
The phone downloads ephemeris data from the cell tower (MSB)
The phone sends its captured GPS data to the cell tower, letting the tower perform the calculations (MSA)
The phone uses cell tower triangulation, totally ignoring the phone's GPS functionality - accuracy is usually reported as being more than 1000m.
...