GPS and battery life on the G1
Update: some of the information we obtained is flat out wrong. Check out the update here: http://www.biggu.com/2009/02/10/updated…
Lots of users/developers assume that if you enable the GPS you will drain your battery more quickly than if you don’t. While this may be true on the iPhone, on the G1 it is actually not true.
Your GPS is simply a radio receiver (k L band). On some devices the radio needs to be enabled to get a ‘fix’, but on the G1 the radio is ALWAYS on. The G1 uses the radio for several phone features instead of using another band. As a result regardless of whether or not you have your GPS on the radio that receives the sat signals is on – the battery life of your phone won’t be different. This is great news for developers.
There is an open source project that provides a service that location dependent applications can use to ‘pre-fetch’ location data so that it is ALWAYS available regardless of whether or not you can get an immediate GPS fix. It also fixes another problem – the time it takes the GPS to obtain a fix (30-60 seconds). Whenever you use ShopSavvy to scan an item we need to figure out where you are to give you a local price. Even if you can get a GPS fix when you scan a barcode, we might not be able to get the GPS coordinates before we provide the pricing results – as a result you won’t get local results. By prefetching your location regularly we can use the last known result which is likely very close to your current location.
Anyway, turn on the GPS!
Thanks for the info, this is good to know! I would imagine that acquiring a current GPS location for the ShopSavvy application isn’t worth it anyway. The user is in a store and not in line of site, and the last know location is more valid…is this a correct assumption?
So what does turning of the “Enable GPS satellites” do if the K Band radio is always on?
“Your GPS is simply a radio receiver (k band). On some devices the radio needs to be enabled to get a ‘fix’, but on the G1 the k band radio is ALWAYS on. The G1 uses the radio for several phone features instead of using another band.”
Huh? This really doesn’t make any sense. I don’t think there is anything in the G1 that communicates on K band (18-27 GHz according to Wikipedia). GPS is all in the 1.xxx GHz range. Do you mean they are using somesort of Software Defined Radio (retunable to different frequencies?) Seems unlikely since that would likely preclude simultaneous operation of multiple radios…
You might recall that all of the original G1′s came with infomration suggesting we disable GPS to conserve battery power. Why would they distribute false information?
Anyway – Do you have any links? I’d love to see your original information source.
Makes sense. But why does the G1 itself state “requires more battery” when unchecked and “deselect to conserve battery” when checked?
Well, the K band is 20 ~ 40 GHz, but GPS (the non-military L1 frequency) is at 1575,42 MHz..
What is the name of the “open source project that provides a service that location dependent applications can use to ‘pre-fetch’ location data?”
The ‘enable GPS satellites’ is more of a privacy feature. If you don’t want anyone to know where you are you should turn it off. Of course the phone company ALWAYS knows where you are. Our Skyhook integration (coming in a few days) will increase the likelihood that we will know where you are in realtime.
I will check with the guys and report.
Thanks for the info. We have learned more:
http://www.biggu.com/2009/02/10/updated-gps-and-battery-life-on-g1/