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Developer
Posts: 403
Registered: ‎04-04-2012
My Device: BlackBerry Z30/Z10/Z10LE/Q10/PlayBook

Location / GPS Performance - Dev Alpha

Hi,

 

  I have terrible problems with Location/GPS performance on my Dev Alpha device. It may take 10-15 minutes or more before I get enough satellites to get a location. No matter what sample app I use, the results are the same. LocationDiagnostics is the one I test with the most, other than my own app. Before I submit my app which needs Location/GPS information, is the Dev Alpha B's or the latest phones any better in terms of Location/GPS performance. Are there any tricks you have found to get things to work better? Are there any settings that allow for just one satellite to be required?

 

Thanks

Developer
Posts: 6,473
Registered: ‎12-08-2010
My Device: PlayBook, Z10
My Carrier: none

Re: Location / GPS Performance - Dev Alpha

GPS is an interesting beast, and quite complex. You're likely not seeing anything the rest of us don't see as well, under the same conditions.

Probably the most important thing to know is that the final devices, with cellular connections, will have Assisted GPS capability which will provide near-instant locks to within a reasonable radius, and generally much faster locks to any radius.

Without the assisted GPS, and especially if you've configured it to use *only* satellite info, you're constrained by physics and the technical design of GPS. If you allow it to use any source, then even on the Dev Alphas it will attempt to use an online geolocation database of known WiFi hotspots, which can help get an earlier position.

With satellite-only, note the following:

1. If it has been a while (a day or three) since the last use, or if you've moved a long distance (some hundreds of kilometres?) since the last use, then any GPS needs to retrieve updated "ephemeris" and maybe "almanac" information from the satellites. This is broadcast very slowly, so it can take 10 minutes, or even 45 or more, depending on conditions, to get all the required info.

2. GPS signals are very weak, and easily blocked by things like brick walls, heavy leaf cover, and atmospheric moisture (e.g. heavy cloud cover or rain). Even your hand or body is more than enough to interfere, so depending on how you're holding it it's possible that's interfering. We don't know where the GPS antenna is located in the Dev Alphas so it's hard to advise how to hold it: consider putting it on a window sill or in a protected location outdoors, with a clear view of the sky (e.g. in a sealed Ziploc bag) if you are having real troubles.

3. You need a clear view of at least three satellites for any GPS positioning, and at least four to get altitude. The software may require more, depending on various other things, before it can provide what it thinks is an accurate reading.

There are problem other restrictions or cautions that aren't coming to mind right now... I'll update with them if anything more occurs to me.

Peter Hansen -- (BB10 and dev-related blog posts at http://peterhansen.ca.)
Author of White Noise and Battery Guru for BB10 and for PlayBook | Get more from your battery!
Developer
Posts: 403
Registered: ‎04-04-2012
My Device: BlackBerry Z30/Z10/Z10LE/Q10/PlayBook

Re: Location / GPS Performance - Dev Alpha

I hope this isn't indicitive of the performance of the final product. Even when I am standing outside in the middle of the backyard, it can be 15-20 minutes before I get a GPS signal. This would be an epic fail if GPS performance is that poor. People expect a smartphone to have quick access to GPS information. In the exact same location, my 9700 gets GPS information in less than a minute. 15 minutes later the Dev Alpha is still trying..

Developer
Posts: 6,473
Registered: ‎12-08-2010
My Device: PlayBook, Z10
My Carrier: none

Re: Location / GPS Performance - Dev Alpha


Bluenoser wrote:

I hope this isn't indicitive of the performance of the final product.


 

As I just said: Probably the most important thing to know is that the final devices, with cellular connections, will have Assisted GPS capability which will provide near-instant locks to within a reasonable radius, and generally much faster locks to any radius.


Peter Hansen -- (BB10 and dev-related blog posts at http://peterhansen.ca.)
Author of White Noise and Battery Guru for BB10 and for PlayBook | Get more from your battery!
Developer
Posts: 403
Registered: ‎04-04-2012
My Device: BlackBerry Z30/Z10/Z10LE/Q10/PlayBook

Re: Location / GPS Performance - Dev Alpha

Peter,

 

  I understand about the assist, the problem is that I was testing both the 9700 and the Dev Alpha with cellular connection turned off so they were on a level playing field.

Developer
Posts: 6,473
Registered: ‎12-08-2010
My Device: PlayBook, Z10
My Carrier: none

Re: Location / GPS Performance - Dev Alpha

There are roughly 30 (?) satellites up there, and I believe the device needs to get ephemeris data from each of them, as they come up. If you haven't done much with the GPS on the Dev Alpha before now, your device had none of that info. If you keep testing with it over a period of several hours (or however long it takes for all the satellites to appear at least once in your view of the sky) it should start locking on faster, even after a reboot. At least, until you stop using it again for a few days or a week.

Mine has in the past worked with very quick lock-on, like within 10s of starting my app. I haven't used it since January 4, but just launched a test app to check.

Noting that it's very overcast today, which could affect the results compared to other days, it took 14 minutes to report even one satellite reading. After one minute more, it is reporting only three satellites. If I were to stop it now, and restart the app in about an hour, I'd expect to have to wait a fairly long time again since a different subset of the satellites would be visible. Same thing if I did it a while after that. If I do that all day, however, and start it up again tomorrow, I'll expect to get a lock within well under one minute.

The 9700 likely has recent ephemeris data from when you last had the cellular connection on. Also, if all you've done is disable the data connection but not the actual radio, it could still be using yet another mechanism: cell tower triangulation. For all I know, it could do that even with the radio off (assuming that only turns off the transmitter and not the receiver... I have no idea about that).

Peter Hansen -- (BB10 and dev-related blog posts at http://peterhansen.ca.)
Author of White Noise and Battery Guru for BB10 and for PlayBook | Get more from your battery!