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Managing GPS failures

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jggimi
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(Last edited by jggimi; 10th February 2011 at 04:31 PM.) Reason: typo / clarity
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Default Managing GPS failures

A number of us, on a variety of ROMs, including stock, have had difficulty getting our GPS systems to acquire a location fix. This can be temporary, or may happen so often it can appear permanent.

Background

When there is satellite reception, it can take a GPS receiver as much as 12.5 minutes to acquire a fix, depending on the number of satellites being received and their relative positions in the sky. To speed this up, our phones use a technology called Assisted-GPS (A-GPS), using location information obtained via mobile data and/or WiFi connections to more accurately and quickly determine a position.

Sometimes, A-GPS data seems to be incorrect, leading to no location fix.

What can we do?

Option A

The GPS Status application, available from the Market, can show you the location, signal strength, and acquisition data from GPS satellites above. It can also flush and reload Assisted-GPS data. This will clear any existing A-GPS aberration, and reset the acquisition sequence.

Option B -- Root required

Google provides Assisted-GPS data to Android phones via an A-GPS standard called Secure User Plane Location (SUPL). Cyanogen's team has determined that for some CM ROM users, disabling Google's SUPL connection in the phone's GPS receiver configuration can improve fix speed. As I understand it, his team is not yet sure of the root cause.

I'm not on Cyanogen's team. Even so, I could guess at a root cause, but it is only a guess. Perhaps the data packet is never received, due to a problem at the server. Perhaps the data packet is received but is missed by the GPS software. Perhaps the data packet is invalid and rejected, but a new replacement packet is never received and the GPS software just waits ....

Whether those guesses are right or wrong doesn't matter. When Google's SUPL service is removed from the phone, other A-GPS location data is used, allowing a GPS fix to proceed. Reportedly, with good speed. From my own experience, also, it seems to work well without SUPL service configured.

1. Mount the /system partition read-write. This can be done from adb, from the Root Explorer application, or from a terminal emulator

2. Edit /system/etc/gps.conf, and remove the lines that begin with "SUPL". For CM7, as an example, this is lines 5 and 6, "SUPL_HOST=supl.google.com" and "SUPL_PORT 7276"

3. Reboot.
 
Lockeskidney
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i use gps status when i'm having issues. it works pretty well

is this pretty standard for most devices...gps issues?
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jggimi
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One resolution that seems to work consistantly for me when in a "no sats" situation is to flush A-GPS data and immediately reboot.

The cause seems to be multiple apps having requested location data (such as browser and map), and may be related to the ROM I use (CM7), but this fix works for me every time.
 
neidlinger
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Quote:
Originally Posted by Lockeskidney View Post
is this pretty standard for most devices...gps issues?
Nope, i've never had a problem with my GPS.
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burnz78
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had GPS issues when i was using CM7 nightlies prior to the RC1 release. but since flashing to RC1, GPS has been working flawlessly and barely takes 3-4 seconds to get a location fix.
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skeene85
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I want to try Option B on my Evo before I try flashing a new radio. I'm rooted and using CM7, so I thought this would be an easy first step.

Even after the mount system app says it has successfully mounted with R/W access, I cannot edit the file with a text editor like this.

I know Google is my friend but alas I give up, I cannot figure out how to edit that file. What am I doing wrong?
 
cevi
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Originally Posted by skeene85 View Post
I want to try Option B on my Evo before I try flashing a new radio. I'm rooted and using CM7, so I thought this would be an easy first step.

Even after the mount system app says it has successfully mounted with R/W access, I cannot edit the file with a text editor like this.

I know Google is my friend but alas I give up, I cannot figure out how to edit that file. What am I doing wrong?
Just install SQL Editor from market, and you are good to go.Other alternative is to copy the gps.conf file to your pc,make a backup of the original and then edit it with Notepad or some similar text editor and then bring back the file to the root of the phone.Just be careful to set the permissions as they were on the original conf file.
 
THEindian
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Originally Posted by cevi View Post
Just install SQL Editor from market, and you are good to go.Other alternative is to copy the gps.conf file to your pc,make a backup of the original and then edit it with Notepad or some similar text editor and then bring back the file to the root of the phone.Just be careful to set the permissions as they were on the original conf file.
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