First fix, A-GPS data, enabled network location, "Use Wi-Fi Networks / Cell towers", "High accuracy"

Arpad Orfi shared this question 11 months ago
Answered

Dear All,

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?

Thanks,

Arpad

Comments (6)

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The use for me is I do not always have a cell signal.

If you want to try a test put your cell phone into airplane mode and launch locus.

See how long it takes to get a fix.

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Good day Arpad,

I do not know exact algorithms that are on background of this process, but I'll try to give answers based on my years knowledge of work with Android devices.

1) I think that enabled/disabled "Network location" has zero effect on speed of GPS fix. Using of this inaccurate location is suggested only to provide "some" location, before more precise GPS location is available, or for some cases, where you do not need to know precise location.

What should have big impact, are A-GPS data downloaded from internet (not directly from device manufactures). This A-GPS data contains some fresh parameters that allows to faster compute complicated computations of your location based on received GPS data.

2) I believe that "Network" location and "GPS" location are not connected. Database of cell towers is needed to compute triangulation on earth, Almanach is used to faster compute equations from received satellite information.

3) First paragraph - it's true. As a developer, I may send request to system to download A-GPS data, but I have no known method, how to check if they were really downloaded. Anyway when they are downloaded, this should be handled by system automatically.

That's my two cents. Most of other questions should be deducted from my answers above. Hope this helps.

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Thanks Menion,

Your answers help, but some questions remain.

So I may conclude that my device (Sony Xperia SP) works flawlessly in terms of GPS device and A-GPS data, regardless of any hocus-pocus of ‘GPS Status & Toolbox’ background process and its alleged data download.

This is the reason I have started to think about these questions, since I didn’t understand what the use of ‘GPS Status & Toolbox’ is.

Especially if the seamless background process of downloading A-GPS data is handled by the Android operating system.

Then why the hack would anyone need 'GPS Status & Toolbox' on an Android device that has let’s say Android 4.1 or higher?

And the big bonus question is, if 'GPS Status & Toolbox' is allegedly capable of downloading A-GPS data, then why wouldn’t any soundly written navigation app be able to download that same data when needed?

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2

You are welcome.

Well ... and who say that this app, "GPS status" is "needed"? This app is nice tool that display current state of received satellites, some sensor values and well ... magic button "reload A-GPS data". I discussed this problematic, with app developer few years ago. What he do in his app, is exactly same what Locus do in "Settings > GPS > Reset A-GPS data" :). And it's not an magic ... read here: http://stackoverflow.com/a/4971275/836138

From my point of view, "GPS Status & Toolbox" is nice tool that display current state, but nothing special. Anyway people share glory feedbacks about it, so why not ... sometimes information that this app helps is good enough to help (even if nothing changes) :). And maybe author after all these years added some more "magic" into this app, only he knows. For this answers is a lot better to ask directly author of this app then me. I remember he was a nice responsive guy.

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I have suspicion the GPS Status application stood behind my long term troubles with frequent freezing of GPS in my Sony Xperia M dual. After unistalling GPS Status my GPS in Locus works very good, and rare loses of GPS are often autocorrected or I set GPS OFF/ON in Locus.

Major issue was probably using Sony specific super saving mode Stamina, as it was easy not being aware it is activated. I had set Locus as an exception for Stamine activation. Android often reports these exceptions deny Stamina activation. But this report never happened for Locus before.

I have realized GPS works fine if Stamina mode is not active. But I have also realized, that, after GPS status uninstall, Locus denies Stamina activation as well, if it was left activated by mistake. But this did not happen before even if it should happen.

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Hello Libor,

I have experienced problems with Stamina from the get-go, hence I disabled it after a few days of usage and realizing that it is me who wants to control what happens in the background not Stamina.

The user still can set various things in Android settings (or in Low battery mode in my Sony Xperia SP), and if that is not sufficient, then one might try Greenify on a rooted phone.

Thanks for your comments – I always enjoy your insightful comments.

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