GPS affected by mobile/SIM

[Guest Searcher2]

I bought another San Francisco and received it today. The main use I have for the SF is GPS so I immediately went for a short walk with both my SFs to make sure the GPS was working fine on the new one. The tracking on it seemed to be worse so when I got home I checked them both out with "GPS Status". Both seemed fine. However, when I set them down next to one another with both running MM Tracker (which tracks your route) after 30 minutes the new one said I had done over a mile and the route was all over the place centred on my actual location - even though it hadn't moved. The old one was fine - 0 miles recorded. I was all set to return it when it occured to me that the old SF had no SIM in it whereas the new one did and was getting a signal from Orange. I removed the SIM from the new one and the GPS signal was fine!

I thought I would bring this to people's attention - I haven't seen this mentioned before and have tried to search for the issue I was having.

Anyway - I intend to use my SF for GPS and occasionally for internet (but unlikely for calls). Is there a way I can disable the SIM without removing the SIM from the SF so that I can just enable the SIM when I want internet?

EDIT : Answered my own question. Putting the SF into Airplane mode disables the wifi/mobile functionality but leaves the GPS working so it does the trick. I guess it's not that useful to most people who actually use the SF as a phone! :mellow:

Edited May 7, 2011 by Searcher2

[Guest Airazz]

I don't have OSF yet but I already did some searching and it seems like SIM assisted GPS navigation can be disabled, leaving just GPS. You'll need some maps app (TomTom, Garmin, etc.) as tracking without SIM assistance will not attempt to download maps from GoogleMaps.

[Guest Searcher2]

I don't have OSF yet but I already did some searching and it seems like SIM assisted GPS navigation can be disabled, leaving just GPS. You'll need some maps app (TomTom, Garmin, etc.) as tracking without SIM assistance will not attempt to download maps from GoogleMaps.

I was not using 'SIM assisted GPS navigation'. I was using MM Tracker which doesn't use the internet or wifi at all. I just downloaded a widget which toggles Airplane mode on and off so I could pop it on my home screen for easy use when I use MM Tracker. I tested it again yesterday and having the SIM active really does affect the GPS reception adversely. I got a lot smoother (accurate) routes when I had it in Airplane mode.

[Guest Roph]

Assisted GPS queries cell towers for their rough location. I believe this happens anyway. Even if you're not on any network or have an invalid SIM, there's still some communication with towers.

Perhaps it could also be cached location data playing a part?

Edited May 9, 2011 by Roph

[Guest Searcher2]

Assisted GPS queries cell towers for their rough location. I believe this happens anyway. Even if you're not on any network or have an invalid SIM, there's still some communication with towers.

Perhaps it could also be cached location data playing a part?

I doubt it could be cached location data as it was a brand new phone. The results were reproducable too. Go to Airplane mode and leave the phone static - no route is plotted on MM Tracker i.e. stable fix. Switch the SIM back on and a route is plotted i.e. signal 'dancing'. If it is clear open sky the problem is not so noticeable but with partial cover (which can happen a lot when walking) it really is an issue - the route tracked when walking down a straight road can resemble more of a drunk man's stagger. For most applications (e.g. car sat nav) it won't be an issue and it's not too bad even for walking but you will get a better fix without the SIM on.

[Guest sambartle]

Does MM Tracker keep the screen active (fully on) all the time?

If not then this is possibly the correct behaviour. (although I can see on the market it only asks for fine location permissions not coarse.. though im not sure what android does if fine isnt available in that case)

With my SF with the screen on and the sim active the GPS works 100% fine with no noticeable wobble.. Location does however almost always fall back to triangulation when the screen is off even though I have GPS on.

Edited May 9, 2011 by sambartle