Crap GPS-Signal detection

[falumas]

When I had bad GPS reception during the recording the overlay goes bananas (not a fault by this software).

Would it be possible to add a min and max speed and if the speed is outside those limits skip adding the overlay for those frames.

I am not the worst person who ever went down a slalom slope, but the 30'000kmh that I sometimes get on the overlay might be a bit exaggerated. My experience after that I have processed 40-50 videos, where maybe 10 had crap telementary, is that once the speed comes below 100kmh it fairly quickly after that starts to be good. Or it just stays at 0 if no signal was picked up.

[armanddp]

There's a precision (or rather lack of) score in the GoPro (gpmd) metadata. Which should be quite useful to filter out the bad readings. While I couldn't find a reference to it quickly scanning I was pretty sure it might already be in use on this great project.

GPSP | GPS Precision - Dilution of Precision (DOP x100) | 1 | n/a | Within the GPS stream, under 500 is good - https://github.com/gopro/gpmf-parser

GPSP (or DOP) see https://en.wikipedia.org/wiki/Dilution_of_precision_(navigation)

[falumas]

If possible the solution suggested by @armanddp looks much better and that will allow the people on ISS to still use this awesome software as well.

Parameters that allow to set limits on these two values would be much better, if the data quality of those values are high.
GPSF | GPS Fix | 1 | n/a | Within the GPS stream: 0 - no lock, 2 or 3 - 2D or 3D Lock
GPSP | GPS Precision - Dilution of Precision (DOP x100) | 1 | n/a | Within the GPS stream, under 500 is good

I will send you a file later that contains a really bad signal the first half of the movie, but gets good enough GPS signal second half to create a feasible overlay.

[KyleGW]

I like the options presented above a lot. At one point for a video I really wanted to get right, that had bad GPS data, I exported it to a GPX, did some analysis in excel to see what the right values were for "not reasonable distance to have traveled based on the points around it", and then used that to iterate through using python and throw all the unreasonable values out. Having the max DOP used would be great. Even just a constant in the code somewhere that can be changed by advanced users would be a good start. (But then if going that far, not much more work to make it another command line option to change it)

[time4tea]

Good to know! If something is annoying, please do raise an issue to let me know... then I can do something about it.
It might not be possible to address every single thing... but at least I can think about it :-)

[falumas]

I have sent you an email to a slightly modified adress of gopro-overlay [at] time4tea.net with download Links for the file that has a mix of data quality of the GPS Signal. Please give me a notification once you have downloaded them so that I can remove them.

[time4tea]

@falumas hiya - thank you - yes got your email - downloading them... will take a while as my internet is not that fast..

[time4tea]

@falumas @armanddp @KyleGW - you should find some changes in latest version 0.77.0 that improve the situation a bit. please let me know if they are useful for you.

[time4tea]

Hiya. Great! For the altitude, yes. For the route... well its a bit more difficult, as I'm already removing all the points that are "not locked" and also using a mechanism to try to determine which other points, that are marked as locked, are actually not. It's a bit.of a guessing game. I can see if there is something obvious about the data, so I can filter it out, but I'm not sure right now.

I'll see what I can come up with.

To see the actual data, by the way, you can use gopro-to-gpx and then load the gpx file into a gpx map on the Web... you.can see that a lot of bad data is already filtered...

[time4tea]

@falumas maybe the changes in the latest version will make a difference? 0.79.0... please let me know if the changes in that release were useful for you.

There are now a number of controls to clip gps points that fail certain tests - e.g. too fast, high DOP, or outside bounding box.

The chart component or a metric field can show the DOP as an overlay on the movie, or you can use gopro-to-csv to see this in a csv file.

[falumas]

I am trying it out, some of my video seems though to have so crappy data that nothing will help. A GoPro 11 is heading my way, hopefully that one will produce better GPS data. These changed did though help me for plenty of videos.
Once again a big thanks for your help.

[falumas]

I have now testet it quite a bit and it is working fine. The new parameters are very helpful
--gps-speed-max --gps-speed-max-units --gps-dop-max

The only thing I would change is the default value for max speed which seems to be 70kmh at the moment. 500kmh (which is enough for most landbased stuff) or so is probably a better default value. Both for skiing and bicycling 70kmh is too low, atleast here in Switzerland where you either go 5kmh upwards or 80kmh downward if you are using something that glides or rolls.

By crappy GPS-data I mainly get over 10000kmh.

[time4tea]

thanks for letting me know - that is really useful! - I'll raise the limit... I'm glad to know that the new options are working as they should.

If you have a frame with an overlay that I could add to the examples that would be amazing - if you are able, please send to gopro-overlay [at] time4tea.net and I'll add it. Of course, please don't feel obliged.