How does AGPS reset work?

[M3Stang]

I was reading about gps reset apps just because it sounded interesting and I just wanted to know how they work? Like can a reset fail? What is it resetting? Can you remove a reset app after it does a reset? Or does the phone become completely dependent on the app to use gps? If it should fail, is the gps bricked?

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[worwig]

This is my understanding. I could be wrong......

For a GPS receiver to work, it must have a detailed 'catalog' of information in the actual satellites. When you first turn on a GPS receiver, or after the receiver has sat unused for a long time, or moved a long ways while off, it must acquire this catalog from the satellites that it can see clearly. As in, if you are indoors with a poor view of the sky, this may literally take hours, or never. Outdoors, it should be much faster.

Another way of looking at it is, the GPS has no clue where you are on planet earth, so it has no clue which satellites to look for. It initially takes a long time and a clear signal to even estimate where you are, to even know what satellites to acquire before it can triangulate and exact location.

So to get around this on phones, they came up with aGPS. The aGPS data tells the chip set roughly where you are, so that it quickly knows what satellites to try for. It just attempts to speed up the process.

When I first got my Note 4, I used GPS Status to reset the aGPS data. That didn't help much and my location was inaccurate, and whenever I started a GPS program, it took a while just to get a poor location. So I turned on my GPS app, plugged into external power, and sat the Note by a window for about 1/2 hour. Now it always gets an accurate GPS lock within a couple of seconds when I use it.

 

[sparksd]

Yeah, the "catalog" is the ephemeris data and downloading from the satellites can take a while. A simple description of AGPS here:

GPS vs. aGPS: A Quick Tutorial | Windows Central

 

[M3Stang]

This is my understanding. I could be wrong......

For a GPS receiver to work, it must have a detailed 'catalog' of information in the actual satellites. When you first turn on a GPS receiver, or after the receiver has sat unused for a long time, or moved a long ways while off, it must acquire this catalog from the satellites that it can see clearly. As in, if you are indoors with a poor view of the sky, this may literally take hours, or never. Outdoors, it should be much faster.

Another way of looking at it is, the GPS has no clue where you are on planet earth, so it has no clue which satellites to look for. It initially takes a long time and a clear signal to even estimate where you are, to even know what satellites to acquire before it can triangulate and exact location.

So to get around this on phones, they came up with aGPS. The aGPS data tells the chip set roughly where you are, so that it quickly knows what satellites to try for. It just attempts to speed up the process.

When I first got my Note 4, I used GPS Status to reset the aGPS data. That didn't help much and my location was inaccurate, and whenever I started a GPS program, it took a while just to get a poor location. So I turned on my GPS app, plugged into external power, and sat the Note by a window for about 1/2 hour. Now it always gets an accurate GPS lock within a couple of seconds when I use it.

Very interesting and detailed post thanks! So are you saying that your phone had bad signal until you reset it? Is the data that's currently on a phone that hasn't been messed with considered "stock" or is it constantly changing anyway? And then can you clear the data so that the phone automatically finds the correct information on its own?

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[worwig]

Very interesting and detailed post thanks! So are you saying that your phone had bad signal until you reset it? Is the data that's currently on a phone that hasn't been messed with considered "stock" or is it constantly changing anyway? And then can you clear the data so that the phone automatically finds the correct information on its own?

My phone was working poorly because it was new. Any new GPS device will not work, or will work poorly, until is has a full catalog. Doing the aGPS reset with the GPS STATUS software didn't help a bit if I recall. What helped was time and a clear view of the sky. The data does change, but I believe it is good for a few weeks. It should keep itself updated reasonably well unless you turn of the GPS for weeks.
Bring up GPS Status and you should get a fix in seconds IF you are by a window. If it doesn't, let it run for an hour, with a view of the sky. It should show a dozen or more satellites that it has a fix on (green).

 

[M3Stang]

My phone was working poorly because it was new. Any new GPS device will not work, or will work poorly, until is has a full catalog. Doing the aGPS reset with the GPS STATUS software didn't help a bit if I recall. What helped was time and a clear view of the sky. The data does change, but I believe it is good for a few weeks. It should keep itself updated reasonably well unless you turn of the GPS for weeks.
Bring up GPS Status and you should get a fix in seconds IF you are by a window. If it doesn't, let it run for an hour, with a view of the sky. It should show a dozen or more satellites that it has a fix on (green).

So the app forced it to catalog?

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[Bosbouer]

The easiest way for me to keep the gps almanac up to date and ready to aquire a fix quickly, is to keep location on BUT not the high accuracy mode. Only wifi and gsm is sufficient to tell the gps app of you choice where in the world the device is and in which quadrant to search for satellites to use on latch onto. My Favourite Gps app is Gps status. Just selecting the app from the drawer places the gps in active mode. Within a few seconds you will have 3 to 4 stats locked and a position fix.

 

[worwig]

So the app forced it to catalog?

Any GPS app, used for a LONG time with a CLEAR view of the sky will acquire a full catalog. Turn on Google maps, go outside for an hour. I know that actual GPS devices, they recommend that you not drive around for the initial acquisition.

How many satellites have a lock when you are near a window or outdoors?

 

[M3Stang]

Any GPS app, used for a LONG time with a CLEAR view of the sky will acquire a full catalog. Turn on Google maps, go outside for an hour. I know that actual GPS devices, they recommend that you not drive around for the initial acquisition.

How many satellites have a lock when you are near a window or outdoors?

Not sure. I'm using an app called "gps status" it's really simple with a sort of hemispherical map with a compass dial with the satellites and then a map below it to show my location.

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