First of all, I captured some packets while using Google Maps Mobile (currently version 3). As you might know there are a couple of techniques available to geolocate a phone. First of all, modern phones have GPS receivers. GPS is probably the most accurate location mechanism. Furthermore, information about nearby GSM/UMTS base stations can be used to localize a phone. This may be combined with triangulation on the phone itself.
Most surprising to me was the fact that the G1 also submits information about nearby Wifi base stations. Wifi cells are usually much smaller than GSM/UMTS cells and can provide more accurate results (and once location information is associated, it even provides localization in areas where GPS does not work such as in buildings or tunnels).
But, two important questions arise:
a) Why does the G1 send information about Wifi and GSM/UMTS base stations, even if GPS is available and enabled?
b) How does geolocation work with Wifi base stations? After all, one needs to have a database with all the base stations and their corresponding location in order to use it for localization.
I guess, there is one answer to both of them. It seems as if Google builds up its own localization database like so:
a) Make all users of Google Maps Mobile enable all "sensors", i.e. GPS, GSM/UMTS and Wifi
b) Submit information from all of the sensors to Google
c) If there is a user that can only provide e.g. Wifi base stations around, correlate this with known Wifi base stations in the database and use the GPS or GSM/UMTS information available which was submitted by other people beforehand
Here you can find a wireshark capture with some stuff highlighted.
Apart from that, it seems as if any device using Google Maps Mobile acts in the same way as described above for the G1.
My overall impression of the G1 is not very positive (it's a freak tool). The phone is heavy (my personal impression), however, the touchscreen works fine. All in all, I think it is not fully mature and would not recommend it. The version I tested had Android 1.0, I guess a lot could be improved by changes in the software.
