- 03-17-2011, 08:48 AM #51
- 03-17-2011, 10:19 AM #52iPhone Newbie
- 39 Posts
I've been busy with work, but have continued testing this. All I can conclude is that the only way I can get reliable GPS is when I'm in an area where cellular signal is non-existent or when I manually turn off the cellular data in the phone settings. Now, the big issue is tracking down the proper individual(s) to report this to, assuming they've not already discovered it and are (hopefully) working on a fix.
- 03-17-2011, 10:59 PM #53
Same here. Communicating with Apple and MotionX
Here is a reply email from me to MotionX. It explains most of what I'm dealing with. Same intermitent GPS signal. Not present with native app.
Thank you for your response. I am actually quite familiar with how the phone and GPS in general work. I'm a software engineer myself. The signal strength I am referring to on the iPhone is in the GPS Drive app on the "my position" screen there is a signal strength indicator which shows satellite reception, or "Triangulation" if the unit is using the assisted GPS function of the iPhone to collect location information from the cellular network. In the native maps app if I leave the device on for five minutes in a completely stationary position, with the auto screen lock setting turned off, the blue dot keeps "pinging" indicating it has GPS signal. If I do the same thing in your app at some point the GPS signal strength indicator will go all the way to nothing (and the spinning globe will turn red), and then almost immediately the signal strength will bounce back to full strength and the globe will turn blue. This is the signal strength on the "My Position" screen in the app, not the cellular signal strength indicated in the top status bar. I also think this happens less frequently when cellular data is turned off. This indicates to me there is some kind of unwanted behavior associated with the GPS antenna and the 3G data antenna. They are on the same chipset in the Verizon iPhone (as opposed to the GSM iPhone where they are discrete). I don't know if it is possible that Apple has designed there native Maps app slightly differently to address this different chip design. Also, it seems that it might be related to tower handoffs on the CDMA network. Again, I know you get the same information that the maps app does, but the native app does not have this problem. Also, you did issue an update to the GPS Drive app when the Verizon iPhone came out to address some compatibility issues so maybe this update did not fully patch the application for use on the Verizon network. Again, I know cellular and GPS are discrete signals, but in the Verizon iPhone they are received by the same chipset. It is possible that there are some different characteristics to the way the data is output from this chipset and therefore needs to be compensated for in the application. For example, maybe the device isn't in fact losing it's GPS signal but because the data footprint of the chipset might be interpreted by your application as a loss of signal when in fact there is still a signal. The GPS Drive app is very good at getting a signal even inside, which is why its loss of signal outside for very brief periods doesn't make sense.
Hope this helps a little. Here is a link to a blog that is currently active on this exact issue. Read through the posts (couple pages). It's not just your app but a lot of the third party navigation apps.
Update: I just went for a walk around my neighborhood loop. Open view of the sky the whole time. I turned the screen lock of and walked the loop first with the iPhone open to the native Maps application. The app tracked perfectly with the small blue circle pinging the entire time, no loss of signal. The loop is about 9 minutes. I did the same loop this time with the GPS-Drive app open to the my position screen so I could watch the GPS signal bars. Every minute or so the signal would spontaneously drop to nothing and the globe would turn red. About ten seconds later the the signal would return and go back to full strength, the globe would turn blue. This continued every minute or so for the duration of the loop. Both times around the loop the only app running on the device was either the Maps app or the GPS Drive app. All other apps were closed out in the app switcher drawer before beginning the test. After completing the loop the second time I end I opened the native app and then GPS Drive. As soon as GPS Drive would lose signal I would "fast app switch" to the native Maps app and it would be tracking (pinging). When I returned to the GPS Drive app it would return to normal shortly. I also own your other app, MotionX GPS. I opened GPS and tried this app next and did not have the same loss of signal I experienced with GPS Drive. This was the first time I have done this test with GPS so I can't say how accurate it was, but as of now it appears as though the problem may be isolated to GPS Drive and not GPS. Again, this was a quick test of GPS. The problems with GPS Drive are consistent and reproducible. They do not exist under the same conditions with the native maps app.
- 03-18-2011, 03:04 PM #54
- 03-18-2011, 03:12 PM #55
- 03-18-2011, 03:15 PM #56
More from MotionX today.
In this letter MotionX acknowledges that cellular or wifi location data can disrupt the GPS signal. However, this still doesn't explain why it loses reception after it has a lock.
Thanks for your patience as I know this issue can be very frustrating. After further investigation of your concern I have some helpful information with may shed some light on the situation.
Problems can arise if a cell tower is incorrectly mapped by your service provider. Let's say they incorrectly map a cell tower that's in Oregon to be in Texas. Now everyone is Oregon who's trying to acquire a GPS signal is either shown they are in Texas (based on the tower identifier) or they are unable to acquire a GPS signal because the iPhone is listening for the wrong satellites. This particular situation has happened and you can read about it here:
The short term fix was for users to turn off their 3G service. Then the GPS signal was acquired quickly. The same problem can arise if a WiFi access point is incorrectly mapped to the wrong location in Skyhook's database. If their database shows the access point is in Santa Cruz, but someone moves and takes the access point to Utah, they may have trouble acquiring a GPS signal while in proximity to the access point until the location is updated in Skyhook's database.
As for why the native maps app works, I can only speculate Apple doesn't show when a signal is lost immediately in the map app as we do.
I hope this information helped. Please contact me if I can assist you with anything else.
- 03-18-2011, 03:33 PM #57
- 03-18-2011, 04:09 PM #58
- 03-18-2011, 04:43 PM #59
Perfect GPS with cellular data off.
I just did a test drive in an area with open sky, but MotionX continually loses reception for brief moments. This time I turned off the 3G cellular data as suggested. The GPS reception didn't lose signal once and normally would have lost it every few minutes. I too have noticed that it seems to lose reception in the same places. I am convinced this has something to do with the location data being sent from the towers, or the way the phone handles that data. It seems like the phone receives updated tower location data each time it interacts with a different tower and this information is screwing with the GPS momentarily. Almost as if it resets and then quickly locks on again. Unfortunately when I call Apple all they do is say they haven't heard of this problem and to retire the phone and set up as new. I really don't think this has anything to do with the solution and with a few hundred apps, tons of music and pictures this is no small task. Just reorganizing my apps into the appropriate folders will take a significant amount of time. I've already read of people replacing their phone and having the same problem. Also, it definitely seems location based so perhaps some tower aren't causing these problems and therefore not everyone has the issue. That, or most people don't look that closely and just use the built in maps.
- 03-18-2011, 04:52 PM #60
- 03-18-2011, 05:18 PM #61
I got my iPhone 2 days ago and downloaded navigon and tried it out yesterday. It was a 52 mile trip that started at the base of mountains and ended near the beach
It took a few seconds to acquire the signal initially but after that it worked flawlessly. Not once did I lose the signal, even when driving through canyons in which I typically lose reception. When I veered off course the app rerouted me right away with no loading times. The speed it projected me to be driving was only 2 mph off of my actual speeds. I highly recommend this navigation app
- 03-18-2011, 05:20 PM #62
- 03-18-2011, 05:40 PM #63
- 03-18-2011, 05:49 PM #64
- 03-18-2011, 06:10 PM #65
Part of the issue may be the cellular assisted "AGPS" - which includes knowing where the tower your cell phone is connected to is located - if the database the 'AGPS' looks up the cell tower is in is wrong, as talked about above - it's going to confuse the (bleep) out of the app software if it's not written well. You may be in an area where one or more of the reference listings for towers in the database is seriously hosed. Here in my area, a few of the former Alltel towers would show a location of the switch they were connected to - because that's how they apparently got listed... and on the first HTC droid phones, the weather widgets were always confused as (bleep) because of it.
- 03-18-2011, 06:35 PM #66
- 03-18-2011, 06:37 PM #67
- 03-18-2011, 06:39 PM #68
- 03-18-2011, 06:42 PM #69
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- 03-18-2011, 06:45 PM #70
- 03-18-2011, 07:04 PM #71
- 03-18-2011, 07:19 PM #72
I just turned off my wifi and made sure I had a good connection to Verizon's 3G network. Then I did a look up of my IP Address at www.whatsmyip.org. According to my current IP information I'm located somewhere in Connecticut, but I am actually in Burlington, Vermont! I looked up some information about the cell towers in my area and found contact info for the caretaker of the Verizon antenna closest to where I'm having all of the problems. I sent a quick message with the towers details and my experience. Hope it does something.
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- 03-18-2011, 10:48 PM #73
I turned off Cellular Data, and Navigon is still acting screwy. TomTom seems to work fine. I have a question though. I thought turning off Cellular data prohibited any kind of communication. But with it off, I am able to make/receive calls and texts. Am I turning off the right thing?
- 03-18-2011, 11:24 PM #74iPhone Newbie
- 39 Posts
I'm not sure about that, Icyhot. I'm almost certain that it's a separate entity from the voice radio and I, too, have received calls with the cellular data turned off during my troubleshooting runs with a GPS app running. As a side-note, Waze continued to call out the turns through the speaker, right on cue, the whole time I was on the call, there again demonstrating how well it can work with other things going on in the back-ground (or in this case, the fore-ground) as long as the data radio is off.
Not sure about the text messages.
OK, I took a tip that the last guy from the Apple store who I spoke with gave me. I went to expresslane.apple.com, tonight, and promptly got a call back. I think I finally got the information into the right hands, this time (i.e. technical support, with emphasis on TECHNICAL, as opposed to customer service). He said he's giving it to the engineers to look at and he'll call me back in 2-3 days with their findings as of then.
I hope this will get resolved in one way or another. I'm just very frustrated that I gave up my other phone for this one and now this is happening.
- 03-18-2011, 11:25 PM #75