Add UUID field to each gps_observation_points record

[edwardfward]

There's currently no way to identify the device that recorded the GNSS observation. Adding a UUID to each record would help identify potential biases present in different phone manufacturers and potentially allow for more accurate characterization of risk.

Recommend adding an imei [string] field to the gps_observation_points table and incorporating the Android API's TelephonyManager.getImei() method to collect and record the phone's International Mobile Equipment Identity (IMEI).

Android TelephonyManager getImei method

Perhaps all of the phone's information could be recorded in a separate table to eliminate redundant data and placing any additional computational burden on the phone?