Today I used the GPS Status & Toolbox application from Eclipsim to reset the cache so that I could start from square one with new Almanac data.
It was raining heavy so I could not go outside to get a fix so I left it in the window. It took around 40 mins to get a lock.
After 30 mins whilst waiting for a lock, I did a power off on reset as it looked like the GPS test program was not working. It was just showing the same 2 Satellites all the time. Once the power returned it was still showing the same two Satellites.
The two satellites were both showing up on the horizon due north using this program. After another ten minutes we had a lock and seven satellites all popped up. So if I am correct the Almanac was downloading taking a long time as Iconia was located in a window facing North.
I turned the GPS Status application off and waited 30 minutes. Again locating in same position I started up the application. The first lock took 26 seconds with 4 satellites and error of 50 Meters . Lock was lost 10 seconds later and came and went every 10 – 20- seconds for around 3.5 minutes, when a continues lock was obtained with error of 5 Meters.
Conclusions
It seems that the GPS is only operational when an application is active. So lock is lost when you close application or bring another Android application active.
Lock takes about 20 seconds if you return to the test application in a short period of time. But after a few minutes it may lock for a few seconds but then take around 4 minutes to fully lock as described above.
I have a GPS in my in car radio this always locks in approximately 20 seconds. I think the GPS must always be active. However I had to disconnect the battery to do some wiring and it took a few minutes to lock next time.
To conserver battery the GPS is not powered on in the Iconia unless an application needs to use it. Hence the 4 minutes to get a full lock. If you change physical location (a few Km ) then it can take longer.
When the GPS is receiving satellite data but has no Almanac data it placed all satellites at same point in sky (due North on horizon) once Almanac data download completes the satellites appear in correct place in sky and lock can proceed.
If the Almanac data is out of date or corrupted when you first acquire your Acer Iconia A500 it may be worth clearing the cache first.
Oldtimer.