[Samsung Infuse 4G] DaMeatMan:
Hey guy's, i've also been having allot of issues with GPS just not being what it used to be, and it's pretty obvioius that this is an issue across the board for all JellyBean roms. I think those who mention that "GPS works flawlessly" don't quite understand the issue with AGPS (Assisted GPS), or they are not quite testing it thoroughly enough to see the problem.

To get an understanding of what AGPS is, and how it helps improve initial lock times, have a read here: http://en.wikipedia.org/wiki/Assisted_GPS

Also, to gain a better understanding of what I mean by "cold start" as you read below, and how it differs from a warm or hot start please read the following: http://m.gsmarena.com/glossary.php3?term=gps

That being said, i have been doing allot of digging in the hopes that someone out there has a solution to the problem with AGPS on the CM10 based ROMs on our phone.

To clarify the problem: AGPS does not seem to work and Initial lock times from a cold start can take several minutes, (this is not normal if AGPS is doing it's job). To clarify further, no one is saying that GPS does not work, it does in fact work, it just takes it's sweet time to lock and it seems to rely on pure GPS to download ephemeris data from the actual GPS birds for satelite lock acquisition, rather then downloading AGPS data over the network to speed things up.

After the initial lock though, GPS functions as it should

. After this point, if you do not use the phone again for several day's, it seems that upon first firing it up again you will experience the long delay in first lock.

This is especially true if you keep GPS services turned off ussually to conserve battery

.

Those who report GPS is fine are probably keeping GPS services on all the time

, and your GPS is probably working in the background at times and obviously will start up allot faster then it would from a cold start. (This is where i believe all the conflicting info comes from!)

The only info i have been able to find that did actually have an impact on my lock times was the thread below.

http://xdaforums.com/showthread.php?t=1881655

I just started testing this out yesterday and i have seen some positive results. But i would caution those of you out there, and say that this is probably not a "fix" per se, but it did help cut down lock times in my case and at the very least it is a very inoformative thread that everyone should read.

What i have realisticly been able to achieve from a cold start is about 75 seconds to lock at the fastest. i.e. GPS services were off, i turned them all on, and now i started up GPS Status or GPS Test to get a lock. After that, as long as I haven't rebooted my phone it takes only a few seconds to lock.

How i tested, i started GPS Status, I then went to Tools --> MANAGE A-GPS STATE -> RESET (This is important to ensure you are clearing previously cached data. We want to make sure your previous cached info does not skew the effects of your changes.

I then replaced the gps.conf with the one contained in that thread, and i also made the change that was suggested in the Notes section that suggested modifying or adding a line in your build.prop file to "ro.ril.def.agps.mode = 1". This change set's your gps to use AGPS in Mobile Station Based (MSB) mode. For reference, setting it to "2" would set your AGPS to function to Mobile Station Assisted (MSA) mode. (Mode 1 - gave me more accurate initial locks at the expense of a bit longer lock times, Mode 2 gave me slightly quicker initial lock times, but was rather flaky and my position drifted quite a bit until GPS was running for quite some time.)

If your curious what is the difference between the two modes, see here: http://en.wikipedia.org/wiki/Assisted_GPS#Modes_of_operation

After making the changes to gps.conf and build.prop i rebooted my phone. When phone reboots, i then go back into GPS Status app, select settings, Tools --> MANAGE A-GPS STATE -> RESET, and then back to settings, Tools --> MANAGE A-GPS STATE -> DOWNLOAD (This should force the phone to attempt an AGPS download, if it hasn't already done so upon launching the app).

I have seen this same gps.conf being used in the newer RemICS-JB build. However based on the lack of feedback in that thread, i don't know if this is the golden fix we have all been looking for.

Even though this may not fix all your issues, i hope at the very least it helps clear up what the actual problem is, and how AGPS is supposed to work.

** Important Notes: **

- The version of the config that i was using was the Download the Google Specific No-SSL v3.1

- If you use the SSL version, then it will also require that you download the certifcate file. It's best to just stick with NO SSL as is explained in the thread.

- You should also note that i have cleaned out all the live wall papers, face unlock, and allot of other crap that i don't use to free up space in the /SYSTEM partition. I now have aproximately 21MB free in this partition. I think at least part of the problem with certain ROM's is that they have the /SYSTEM partition filled to the max with virtually no free space at all. I'm no expert on the subject, but i'm guessing that the AGPS data get's downloaded to this partition some where. Obviously if there is no space, then that would cause issues. Several others have reported shortened initial lock times after making room in the /SYSTEM partition.

- Another mistake people are making when testing AGPS and reporting false info, is having their WIFI on when testing GPS. To isolate the issue guy's you need have wifi off and you need to use a tool like GPS Status or GPS Test that shows that actual lock to satelites. You cannot properly test this and see the issue by using WIFI and turning on Google maps. Google maps will look at your reported wifi position and to you it looks like bamm.. i just got a lock in 2 seconds to withing 50 meters, wow these guy's are nut's, my GPS is awesome. Guess what.. your wifi and google maps is awesome.. not your GPS.. lol

- If anyone is familiar with running log's, it would be great if you could do a comparison of before and after. Showing the log of a completely fresh JB build, that shows that the AGPS data is not being downloaded, and then another log after all the changes above (including freeing up space in /SYSTEM) and hopefully it will show that AGPS data is now being downloaded and utilized. I myself am not familiar with logging data on the infuse, so i cannot and will not call this a fix until someone can actually show with real log's that AGPS data is now being utilized after these mods.