First fix, A-GPS data, enabled network location, "Use Wi-Fi Networks / Cell towers", "High accuracy"
I have some question not just to the developers, but for anybody who understands this subject.
I have GPS Status & Toolbox installed on my phone, but it is not straightforward for me whether this has any advantages from the standpoint of quickness of first fix.
(On my phone the first fix is always remarkably fast, around 3 seconds, even if I start a navigation app several days after the last usage. This quickness of first fix is independent of whether GPS Status & Toolbox is installed or not.)
I have 3 questions to any competent person:
1) Instant first fix is because of enabled network location or A-GPS data
I’m curious whether a quick first fix (not more than 3-5 seconds) is attainable solely by enabling “Use Wireless Networks / Cell tower info” or “High accuracy” in Android settings – regardless of the fact that the phone and the mobile network provides A-GPS service or not.
So does my Sony Xperia SP Android phone give me a 3 seconds first fix because it has A-GPS built-in and the mobile network I use also provides this service (A-GPS data download);
or the quick 3 seconds first fix is not because of A-GPS but instead because I enabled everything in Android settings that pertains to getting location: cell tower, Wi-Fi, high accuracy.
2) Network location vs. A-GPS data
Given that Google’s massive cell tower database is complete, (i.e. it contains all the existing cell towers on Earth, I suppose) and if the user enables using network location (cell tower, Wi-Fi) then acquiring approximate location is instantaneous, then this raises the question whether downloading almanac and ephemerides data https://en.wikipedia.org/wiki/GPS_signals#Navigation_message is advantageous to any degree.
In my interpretation getting network location works even if A-GPS is not available or not working.
3) Is failing to download A-GPS data necessarily a bad thing?
I’ve heard that aGPS capability means that if an application wants the A-GPS data, then it may ask the Android operating system to download that data, but there is no guarantee that the op.system will actually download the data. I don’t know if this is true or not.
Furthermore, I don’t know if the above uncertainty of downloading the A-GPS data is also pertaining if a navigation app explicitly asks for this data when it starts.
Is it possible that because this would happen through the Android operating system, downloading A-GPS data is unsuccessful?
We have to look back again to questions 1 and 2, i.e. does this matter anyway? Android and Google can fix approximate location instantly based upon cell tower (and Wi-Fi) info.
Isn’t this enough to get an instantaneous (3-5 seconds) first fix?
So in the end, what is the use of GPS Status & Toolbox?