GPS cache bug workaround, tested, working
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"
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.
Last edited by ragnarokx; 12-07-2010 at 09:36 AM. Reason: added link to GPS Froyo fix
- 09-18-2010, 09:59 PM #2
- 09-19-2010, 03:02 AM #3
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.
- 09-19-2010, 09:57 AM #5
- 09-19-2010, 10:59 AM #6
- 09-19-2010, 01:11 PM #7
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.
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.
now testing eclipsims "GPS Staus" 9/27 update for same effect
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.
- 09-28-2010, 02:17 PM #10
- 09-29-2010, 11:55 AM #12
- 09-29-2010, 01:25 PM #13
- 09-29-2010, 01:36 PM #14
- 09-29-2010, 04:44 PM #15
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?
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.
- 09-30-2010, 02:51 AM #18
- 10-03-2010, 11:04 AM #19
- 10-03-2010, 06:38 PM #20
- 10-07-2010, 07:00 PM #21"It’s only after we have lost everything that we are free to do anything…"
HTC Touch --> Samsung Instinct --> HTC Touch Pro --> Palm Pre --> Epic 4G
- 10-07-2010, 07:11 PM #22
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.
- 10-08-2010, 01:17 PM #24
- 10-21-2010, 03:59 PM #25