GPS fix bug on Fenix 7 and some other newer models

A bunch of users concated me with an issue that I was eventually able to reproduce myself:

At the start of the app I start the session and GPS (using Position.enableLocationEvents, regardless of the particular method). Position.enableLocationEvents returns no exceptions, all good. However, most of the time the watch does not acquire the GPS fix after that. onPosition is not called and session's GPS accuracy is null. Ocasionally it does connect though, so the issue is random.

If I restart the GPS (again using Position.enableLocationEvents) manually (through UI in my app), it finds the fix fairly quickly.

This affects Fenix 7 and Epix 2 watches, but not Crossover for example. Not sure what oter models are affected.

Did anyone have similar issues? Is there a fix for it (other than restarting GPS a few times)?

jim_m_58 over 2 years ago

For me, what I do in my apps with GPS, is just wait for a QUALITY_USABLE accuracy in "onPosition" before the user can start recording. It's not just newer devices as this can happen on any device. The length of time to get "usable" vaires based on things like if the epo/cpe data is current, where you are (inside a building for example).

So I start GPS and wait for QUALITY_USABLE before creating the session.

for things that aren't even recording, I do something similar, as you'll often get QUALITY_LAST_KNOWN at the start, which could be old and incorrect (for things where I use GPS to get things like weather data). I never use LOCATION_ONE_SHOT, but use LOCATION_CONTINUOUS, and when I get useable, call Position.enableLocationEvents(Position.LOCATION_DISABLE, null); to turn off GPS

MobileDriveway over 2 years ago in reply to jim_m_58

You misunderstood the question. I start the GPS, but "onPosition" is never called, no mater how long I wait.

MobileDriveway over 2 years ago in reply to jim_m_58

It is actually not related to the session at all - I just tested the app without creating a session, still the same result - "onPosition" is never called intill I stop and restart GPS manualy.

jim_m_58 over 2 years ago in reply to MobileDriveway

What version of FW is involved? I'm using 11.15 on an f7x and this is working fine.

MobileDriveway over 2 years ago in reply to jim_m_58

10.44 on F7. I don't use Alpha or Beta - I got enough issues as it is.

MobileDriveway over 2 years ago in reply to jim_m_58

Can you try this app and see if you get GPS fix after the start?

https://apps.garmin.com/en-US/apps/fc9bc58c-aced-400a-961a-e5e6d5a2bbb2

If it doesn't, you can press MENU and select a different GPS mode - that forces GPS restart.

jim_m_58 over 2 years ago in reply to MobileDriveway

I always install beta (often alpha) FW if I'm looking for a FW fix. In the case of 11.15, that was because it's got System 6 and the new stuff like complications.

MobileDriveway over 2 years ago

I found a possible cause for the issue. Before enabling GPS, I do a series of tests to check supported GPS constelations and configurations. I do it by enabling GPS with all configurations as explained here:

https://forums.garmin.com/beta-program/fenix-7-series/public-beta-reports/i/public-beta-v10-xx/bug-apps-with-gps-crashes-at-start-10-39-epix2?CommentId=9f93e382-2d31-4ec0-bfff-ac685abfb5ad

Right after that (in the same Init()) I disable GPS and re-enable it with the option pre-selected by user. That is when it doesn't start. If I delay the restart of GPS for 1 second, it actually works. Perhaps there is some kind of race condition? Maybe some work is still done in background when GPS is I rapidly enable-disable GPS several times?

jim_m_58 over 2 years ago in reply to MobileDriveway

I do it a bit differently. I start with two variable:

		hasNewGPS1=(Position has :CONSTELLATION_GLONASS);
		if(Position has :hasConfigurationSupport) {
			hasNewGPS2=Position.hasConfigurationSupport(Position.CONFIGURATION_GPS);
		}

There are 3 cases.

-Both are false, meaning neither constellations or configuration. Don't try to set anything

-hasNewGPS1 is true and hasNewGPS2 is false. Do as has worked in the past with constellations

-Both are true. You want to use configurations, and this is were hasConfigurationSupport is actually called. You want to check the CONFIGURATION_GPS_* to see if it's valid on the device, and this is also where the sim is kind of out of sync. On the f7x. it says CONFIGURATION_GPS.CONFIGURATION_GPS_GLONASS, and CONFIGURATION_GPS_GALILEO are valid, while on the actual device, I see CONFIGURATION_GPS, CONFIGURATION_GPS_GLONASS_GALILEO_BEIDOU_L1, and CONFIGURATION_GPS_GLONASS_GALILEO_BEIDOU_L1_L5 are valid

MobileDriveway over 2 years ago in reply to jim_m_58

Garmin made a real mess out of GPS config. I'm using the code provided by Travis.ConnectIQ, so they should either fix the code or firmware.

Just so you are aware, the race condition is manifested even if you change GPS modes by rapidly pressing a button on the watch, so even with your method you still might need to introduce a delay in GPS restart.