GPS Desired Accuracy
In general, the GPS receiver tries to achieve within 10 meters of accuracy, though that can vary based on the device's GPS chip, location and how long the device has been running (it can take between 5 and 60 seconds to get a signal from the 4 required satellites). Also, obstructions (buildings and trees) and access to cell towers can affect the results. If additional accuracy is required there special Android devices that can generate GPS values within 2 meters of accuracy.
Time to Lock Coordinates
It depends on the device and how easily it can communicate with the satellite. In both iOS and Android, the first coordinate location event takes a few seconds. The receiver does its best to achieve the requested accuracy (nearest 10 meters); however, the actual accuracy is not guaranteed.
When you first open the Location field, the location manager obtains an initial location fix (the first coordinate location event takes a few second). After that, the receiver generates update events primarily when a more accurate location is read. Once communicating with the satellite it tends to respond very quickly.
GPS Accuracy Confidence
The coordinate accuracy is broken down into the two following properties:
The location’s latitude and longitude identify the center of the circle, and this value indicates the radius of that circle. A negative value indicates that the location’s latitude and longitude are invalid.
Vertical Accuracy (IOS Only)
The value in the altitude property could be plus or minus the value indicated by this property. A negative value indicates that the altitude value is invalid.
We return both of these values in the JSON form submission.
If satellite GPS is unavailable, the device will also attempt to use Cell Tower Triangulation based coordinates if available.
Caching of Coordinates
The app takes uses the live GPS receiver coordinates as location events are triggered. However, the GPS will use the last cached location if within 5 seconds or until there is an actual location update event that has a higher degree of accuracy. Cached locations expire within 5 seconds.