SkyDemon Forums

Assisted GPS (AGPS) and Android

http://forums.skydemon.aero/Topic27564.aspx

By duncans - 12/20/2018 5:50:15 PM

Currently using an iPad mini2 with a Dual150 external GPS.
I would like to reduce my battery stress and go to a tablet with built in GPS.
Cheaper options appear to be Android, but this is all new to me!.
Looking for advice on which 8" android tablet SD users would suggest. In particular I don't want to make the mistake of going sub £100 but finding the version of Android is useless and/or there is no GPS chip. One concern is the 'Assisted GPS chip'. Looks like many tablets might have this and this relies on cell mast triangulation to support the GPS posistion. This doesn't sound great..
By Daniel_KDF - 12/30/2018 12:14:33 PM

duncans - 12/20/2018 5:50:15 PM
One concern is the 'Assisted GPS chip'. Looks like many tablets might have this and this relies on cell mast triangulation to support the GPS posistion. This doesn't sound great..

Assisted GPS means that your device is able to aquire the Almanac (https://en.wikipedia.org/wiki/GPS_signals#Almanac) via a server on your mobile network, that just takes a second to download. This means you can have a very fast first fix after a cold start.
Without assisted GPS, your device needs uninterrupted GPS reception for 12 minutes to receive the Almanac from the GPS data stream directly from the satellites, thus increasing time-to-first-fix significantly.
Of course, a GPS receiver will always fall back to this method when there is no cell coverage, so assisted GPS is no disadvantage.