A-GPS SUPL library

RE: A-GPS SUPL library

pemar13 — Fri, 04 Sep 2020 07:29:44 GMT

Thanks for the clarification!

/per

RE: A-GPS SUPL library

Heidi — Thu, 03 Sep 2020 08:01:18 GMT

Hi, I just got a reply from one of our GPS experts. My answer to your second question was incorrect, I have now updated my previous comment to reflect the correct answer, which is that we don't support the user injecting their own data into the GPS.

RE: A-GPS SUPL library

pemar13 — Mon, 31 Aug 2020 16:21:29 GMT

Thank you Heidi!

Regarding Q2: Are you saying that the time to first fix (TTFF) is totally independent of the approximate location provided during the SUPL request, which means that TTFF is identical whether or not the cellular network provides any MCC/MNC and CellID (such that Q1 is basically irrelevant from an AGPS point of view)?

Best regards,

Per

RE: A-GPS SUPL library

Heidi — Mon, 31 Aug 2020 09:25:29 GMT

Hi!

1. Looks like you already got an answer.

2. Injecting alternative data into the GPS isn't something we have tried but it wouldn't gain anything. The position received from the SUPL server is just an alternative to the GPS having to download the same data from the satellites itself.

2. Unfortunately, we don't support the user injecting their own data into the GPS. It is something we are looking into, whether it would be beneficial to support this or not. Injecting accurate information into the GPS would indeed help shorten the TTFF.

3. Yes, I've seen this. This can happen when the SUPL session is running in the main thread resulting in the main thread not being available to read the GPS messages coming from the modem. This will fill up the memory shared between the application and the modem, so the IP packet from the SUPL server doesn't get read and the session times out.

Try running the SUPL session in a separate thread.

RE: A-GPS SUPL library

pemar13 — Thu, 27 Aug 2020 12:53:55 GMT

Hi!

Thanks a lot! I tought they were simple coordinates in degrees, but your values make perfect sense as well as explain why the A-GPS works considerably better than without, as I am not so far from the center of Sweden!

Thanks again,

Per

RE: A-GPS SUPL library

anicare-tero — Thu, 27 Aug 2020 07:28:06 GMT

Hi Per,

For your first question: I have wondered that earlier too. I was discussing about that with a Nordic employee and she told me how to calculate the coordinates from those values that SUPL returns.

Lat: 5851520 Lon: 780606
Latitude = 5851520 / (2^23/90) = 62.78
Longitude = 780606 / (2^24/360) = 16.75

So that location is the position the "center" of Sweden and this location is not a GPS location, but an input parameter from the SUPL client to the SUPL server.

For another questions, I don't have any knowledge that would help.