Faild to request location via GNSS

[Mustafa]

Hello, 

I've tried to request the location via AGPS/PGPS via Location sample in SDK 1.8 but it seems that location is only working with the Cellular method. 

I've tried to re-provision the device again as it is described here https://docs.nrfcloud.com/Guides/GettingStarted/Devices/#securely-generating-credentials-on-the-nrf9160

The current modem version is 1.3.1
DKnrf9160,
SDK = 1.8,
Location sample ( west build -p -b nrf9160dk_nrf9160_ns -- -DOVERLAY_CONFIG=overlay-pgps.conf )

the output of the Location sample is

Connecting to LTE...
Connected to LTE
Waiting for current time
Requesting location with short GNSS timeout to trigger fallback to cellular...
[00:00:02.264,404] <inf> nrf_cloud_pgps: Checking P-GPS header: Schema version:1, type:10, num:1, count:42
[00:00:02.264,953] <inf> nrf_cloud_pgps:   size:2006, period (minutes):240, GPS day:15372, GPS time:57600
[00:00:02.265,502] <inf> nrf_cloud_pgps: Checking stored P-GPS data; count:42, period_min:240
[00:00:02.266,418] <inf> nrf_cloud_pgps: num blocks:42, size:2048, first_free:-1
[00:00:02.266,876] <inf> nrf_cloud_pgps: map:111111111111111111111111111111111111111111
[00:00:02.267,303] <inf> nrf_cloud_pgps: Checking if P-GPS data is expired...
[00:00:02.267,730] <inf> nrf_cloud_pgps: Looking for prediction for: GPS sec:1330013602, day:15393, time of day:58402, week:2199, day of week:0, time of week:58402, toe:3650
[00:00:02.268,524] <inf> nrf_cloud_pgps: First stored prediction: GPS sec:1328198400, day:15372, time of day:57600, week:2196, day of week:0, time of week:57600, toe:3600
[00:00:02.269,317] <inf> nrf_cloud_pgps: current offset into prediction set, sec:1815202
[00:00:02.269,775] <wrn> nrf_cloud_pgps: data expired!
[00:00:02.270,111] <wrn> nrf_cloud_pgps: Predictions expired. Requesting predictions...
[00:00:29.068,939] <wrn> location: Timeout occurred
[00:00:29.069,549] <wrn> location: Failed to acquire location using 'GNSS', trying with 'Cellular' next

Could you please tell me how I can get GNSS method working?

Thanks in advance!

Mustafa 

[JONATHAN LL]

Hi,

The purpose of AGPS and PGPS is to provide ephemerides/almanac and other GPS related data directly into the GPS, for a quicker fix. It does this by downloading data from the cloud, and piping that data directly into the GPS.

You are "location: Timeout occurred" her so might not be anything wrong, maybe it is just not getting enough satellites to get a fix. Are you testing this inside or outside with a open view of the sky?


Note: see you commented on this case:https://devzone.nordicsemi.com/f/nordic-q-a/84721/failed-to-generate-jwt did you follow the instructions also?

Regards,
Jonathan

[Mustafa]

Thanks Jonathan for your response, 

JONATHAN LL said:

Note: see you commented on this case:https://devzone.nordicsemi.com/f/nordic-q-a/84721/failed-to-generate-jwt did you follow the instructions also?

Do you mean the instructions for building the project?. it is only about adding -DOVERLAY_CONFIG=overlay-pgps.conf to the CMake command. and for generating JWT I've followed the instructions but I'm not sure if I did all steps correctly, I assume it is fine because the Location Cellular method works fine. 

JONATHAN LL said:

Are you testing this inside or outside with a open view of the sky?

I'm testing it next window to the outside with an open view of the sky. But now is almost winter time so maybe there are some clouds and the sky is not totally clear but I assume that AGPS/PGPS are made for this kind of condition right?

How many satellites does PGPS/AGPS service need to download the exact GPS-related data to the modem?

 

[JONATHAN LL]

Could you try the GPS sample(GNSS), simpel one without the AGPS enabled, se how many satellites you are picking up. 

Mustafa said:

How many satellites does PGPS/AGPS service need to download the exact GPS-related data to the modem?

A-GPS is not using GPS/satellites to download the data, it is using LTE. So trough the internet it is downloading some of the info needed to get a GPS fix. And GPS will always need at minimum 3 satellites in "view" to be able to get a fix. 

Regards,
Jonathan