GPS cache bug workaround, tested, working

**Aero** · 09-18-2010, 08:39 PM

The following procedure is for Eclair only. To fix GPS on Froyo, please see this thread.

Note: thanks to user "boomerbubba" for working on this as well

I have three epics and have been testing GPS functionality for two weeks with quite a number of controlled tests.

As we know there is a problem with old "assistance" (the "a" in aGPS) ephemeris and almanac data in cache. this data can start expiring in a few hours and ephemeris will fully expire in about 8 hours.

The result is that sometimes users will experience the following symptoms in a GPS fail: the Epic will "see" sufficient satellites (4 to 11) but doesn't "use" them (expired ephemeris) or will see no satellites while under clear skies (expired almanac, rarer).

Although some user actions or program identified (eg reboot),and unidentified, can apparently flush the old data out of cache so that the network renews it with valid data, this isn't programmed by Samsung correctly and users intermittently are stuck with bad data in cache preventing lock. I have tested a workaround and it works

TESTED AND FUNCTIONING WORKAROUND:
Enter GPS debug/settings application by typing *#1472365#
click "Setup" tab
click "position mode"
Click "starting mode
Enable "Cold Start"
Back out.

Epic GPS will now call on data network for fresh valid ephemeris and almanac at every programing invocation of GPS, and aGPS fixes will be very fast (usually less than 10 seconds).

There one downside. while cold start will be effectively warm start in aGPS mode (good). That is it will work very nicely in the presence of a 3G or 4g data connection. But absent data connection, ie in Standalone GPS mode, you will be always cold starting (starting with empty cache), meaning fixes will be 5 to 14 minutes if you are not on the network. If you are going to be off the network for a while you can simply set to warm start from same menu.

**caliskimmer** · 09-18-2010, 09:59 PM

Aero, your wish has been granted. Stickying right now.

**tromano#CB** · 09-19-2010, 03:02 AM

I had an interestingconvo w sprint tech support today. My gps was hunting most of the time. I was using google navs and it would take foreeeeeevvvvvver to start. On the phone w sprint, he quickly said we don't support that app, tell me how sprint navigation works, and sure enough it worked perfectly, and has since I've checked it again, so i s the gps problem related to the app or the gps overall.... he also made me do a factory reset and my capacitive buttons now work perfectly.

**Aero** · 09-19-2010, 05:18 AM

Originally Posted by tromano

he also made me do a factory reset and my capacitive buttons now work perfectly.

This is what got your GPS working temporarily.
Please read my post. It has nothign to do with the program using the app, it is a gps driver and or stack issue.. Use of Sprint nav has zero positive or negative affect on whether you actually get a lock.

**jimmyz** · 09-19-2010, 09:57 AM

The capacitive buttons is clearly a hardware problem- I have the stupid back button problem which no number of hard resets or for that matter reloading the stock rom fixes

**murso74** · 09-19-2010, 10:59 AM

"absent a data connection"

does this include wifi? i'm usually home when i start using gps and on my wifi network

**grant3d** · 09-19-2010, 01:11 PM

So, on top of these settings you have "use wireless networks" and "use my location" on? Do those debug settings stick or reset with reboot? Thanks for taking the time to test and post a workaround!

**Aero** · 09-19-2010, 04:08 PM

Originally Posted by murso74

"absent a data connection"
does this include wifi? i'm usually home when i start using gps and on my wifi network

What I mean by absent a data connection is if you out of the country, on a cruise ship or in a rural location with no CDMA or wifi data connection.
It is just a caveat noting that in that circumstance, which is a standalone GPS mode, as opposed to aGPS mode, clearing the cache on every gps use though forced cold start would make for longer times before satellite fix. In short, if you are going out of the country or up to Alaska you probably want to temporarily put it on warm start.

Originally Posted by grant3d

So, on top of these settings you have "use wireless networks" and "use my location" on? Do those debug settings stick or reset with reboot? Thanks for taking the time to test and post a workaround!

a) the settings change sticks with reboot. You can changed it back to factory easily though through the same steps above

b) no, you do not have to enable "use wireless networks". "Use Wireless networks" is a totally different system of obtaining location, which uses tower triangulation. Having this enabled is good for situations where devices such as smartphones do not have a view of the sky. It gives you a less accurate location, does not work well while moving at speed, but will work as as long as you are getting a sprint or verizon signal of any kind, even just a voice signal.

There maybe some confusion on this among some readers as the 'Use GPS" toggle, which is the GPS and aGPS system, does use some data if able. But this is NOT changed by, enabled, disabled or in the least bit affected by the "use wireless networks" system which is a different, secondary and separate location system.

**Aero** · 09-28-2010, 12:26 PM

I am over the next few days testing eclipsims "GPS Staus" 9/27 update for same effect. GPS Status now will attempt to discern gps assistance age, and may better force clearing and upload of cache. I am testing it on one device with warm start without using gps status, one with warm start with using gps status, and one set at cold start.

**boomerbubba** · 09-28-2010, 02:17 PM

Originally Posted by Aero

I am over the next few days testing eclipsims "GPS Staus" 9/27 update for same effect. GPS Status now will attempt to discern gps assistance age, and may better force clearing and upload of cache. I am testing it on one device with warm start without using gps status, one with warm start with using gps status, and one set at cold start.

Thanks. Are you just clearing the cache using the GPS Status interface, or also reloading it? (As you know, these are distinct steps.)

**Aero** · 09-29-2010, 11:41 AM

Originally Posted by boomerbubba

Thanks. Are you just clearing the cache using the GPS Status interface, or also reloading it? (As you know, these are distinct steps.)

I am first attempting with their new cache timer function from the latest update. have you got the latest update of app?

Since we expect a baseline update to deal with 150 cap the test wont be valid until some time after that since gps fails cant ake a while.

**boomerbubba** · 09-29-2010, 11:55 AM

Originally Posted by Aero

I am first attempting with their new cache timer function from the latest update. have you got the latest update of app?

Since we expect a baseline update to deal with 150 cap the test wont be valid until some time after that since gps fails cant ake a while.

Thanks. I did not have, or even know about, the most recent GPS Status version with the feature for autoload of assistance data on startup. Updating my version now.

**phantomevo77** · 09-29-2010, 01:25 PM

I am still searching for GPS after 5 minutes =/. Doesn't work for me and I am in an area with 4 bars of 3G service... *sigh*. Tested outdoors and indoors and nothing =/

**boomerbubba** · 09-29-2010, 01:36 PM

Originally Posted by Aero

I am first attempting with their new cache timer function from the latest update. have you got the latest update of app?

It does seem to me, just intuitively, that if the GPS Status cache refresh works and is run first, that the right startup setting for the GPS would then be Hot Start because the cache is fresh. Does that make sense?

**murso74** · 09-29-2010, 04:44 PM

this gps fix doesn't seem to be helping my problems.... :: sigh ::

**Aero** · 09-29-2010, 08:40 PM

Originally Posted by boomerbubba

It does seem to me, just intuitively, that if the GPS Status cache refresh works and is run first, that the right startup setting for the GPS would then be Hot Start because the cache is fresh. Does that make sense?

Yes, thanks, your assessment does make sense and I will test that way.

It would be great if gps status could handle it because that means absent atimely fix from spt/sam some routine could be written that possibly does this better than gpsstatus, especially more efficiently. eg refreshing cache without an invocation of aGPS or an invocation and full time running of the full gpstatus program which is liable to be a battery drain

There are some odd things showing up. I cannot see the gps status latest version's feature for "cache age" indication moving off of "0". can you?

**Aero** · 09-29-2010, 08:50 PM

Originally Posted by murso74

this gps fix doesn't seem to be helping my problems.... :: sigh ::

murso, sorry to hear that. what are you seeing with GPS status when you invoke in clear view of sky with 3g connection live and good?

Also here is something different about wifi which you mentioned you are using. That is the one case where location by use wireless networks" fix might help. Those of us doing the testing are so adamant about leaving it off for gps testing, because it is a craven red herring by samsung for most users just pitching users to a less accurate systerm

Sprints agps system determines your proper local assistance data to send to you by the tower you are connected location. ephemris and almanac are localized at the tower. but with wifi it is possible the assistance servers have no idea if you are in LA, the florida keys or kalamazoo.

what are following setups doing for you?:
1) clear view of sky, 3g on and active, wifi off, and cold start set?
2) clear view on, 3g off, wifi on, use wireless networking on with rough ('coarse") fix established and then attempt to use agps.

**murso74** · 09-30-2010, 02:51 AM

unfortunalty i dropped my phone in the toilet last night after i posted that. doody phone is going back to sprint and a new one is coming in courtesy of TEP. i'll be testing with my "new" phone for sure

**capitaltpt** · 10-03-2010, 11:04 AM

GPS Status really helped out my GPS. It's not quick and snappy with fixes. I've only had it on for a couple hours since I ran the app, but I'll report back in a day or two and let you know if it's still working

**DaleP** · 10-03-2010, 06:38 PM

Thank you! I have had GPS not work about twice per week exactly as described in the first post, but my wife who is in real estate was getting this problem all the time.

I executed the fix setting both Epics to "cold start" and that problem disappeared on both Epics.

**dragonol2** · 10-07-2010, 07:00 PM

Originally Posted by Aero

TESTED AND FUNCTIONING WORKAROUND:
Enter GPS debug/settings application by typing *#1472365#
click "Setup" tab
click "position mode"
Click "starting mode
Enable "Cold Start"
Back out.
.

Works like a charm and has (so far) solved my GPS problems! Thanx a bunch!!!

**capitaltpt** · 10-07-2010, 07:11 PM

As stated earlier, GPS Status has been my saving grace with it's aGPS download. I've e-mailed the developer about creating a widget or allowing for download of aGPS without opening GPS Status. He was very open to the idea and said he was putting it on his "To Do" list. Good to know the devs can help where Samsung has failed us.

**Aero** · 10-08-2010, 12:44 PM

Originally Posted by capitaltpt

As stated earlier, GPS Status has been my saving grace with it's aGPS download. I've e-mailed the developer about creating a widget or allowing for download of aGPS without opening GPS Status. He was very open to the idea and said he was putting it on his "To Do" list. Good to know the devs can help where Samsung has failed us.

that wont do any more than setting cold start.