Guys, I did a survey using a camera without GPS and an external Garmin GPS, which generated a GPX file. However, I can’t get it to sync properly. I think the GPS date and time were incorrect at the time of recording.
When I upload it to Mapillary, there’s a huge mismatch between the track and the images.
Does anyone with experience know how to fix this? I need to extract frames (I use vid2jpg) and upload them to Mapillary, or at least align the MP4 with the GPX for submission. I’d also like to use the data in QGIS. I’ve tried several solutions, but nothing has worked so far. Any tips? I’m desperate to find a way to fix this!
@jaderbavaresco - if you were recording with a camera without GPS as you mentioned, then in order for the .mp4 video and the .gpx to be in sync you would have needed to start each one at the exact same time. If there is an offset (like you started recording one a little bit earlier than the other) you’ll need to edit either the .mp4 file (for example to trim it) or the .gpx (with a text editor).
The problem begins when a vehicle comes to a stop at a traffic light or due to slow traffic. Mapillary omits moving images of a stationary vehicle. Unfortunately, an artificially generated GPS track continues to run. The images and track then diverge dramatically. It is therefore of little help to start video and a GPS tracker at the same time when recording on separate devices. It is probably not for nothing that Insta first combines the GPS signal and the video signal in the camera and then separates them again when creating the mp4 file. How Mapillary finds the right entry into the GPX track again after removing images from a traffic light break is still a mystery to me.
It would be very helpful if you could optionally turn off this function. This would allow a video and an independently generated GPX track to reach the end of the recording at the same time.
I have already created a GPS track from an ODB-II car scanner recording as a test. However, I ultimately had to give up on this plan because the Mapillary function in question thwarted my plans by omitting downtime. The ODBII recording also enables a usable GPX track through tunnels. ODBII software packages are quite sufficient, as they are used for travel expense accounting and a lot of money is involved. It’s a shame that we do without this sufficient technology from motor vehicle traffic and instead have to contend with inadequate GPS recordings.
@osmplus_org - are you talking about using the Mapillary mobile apps in conjunction with an external GPS receiver? Or are you talking about using an external camera? Could you share on exactly the workflow you’re doing so we can replicate it?
Hi, i have developed a nice tool to sync video with gpx, normally we use it for Kinomap to sync the routes, but i think its a good tool for Mapillary too:
Very cool, thank you for sharing @ridewithoutstomach - so the main use case for your tool is when you’re recorded video with one device and .gpx with another device, and now you want to sync them together, is that right?
Yes, the main feture is syncing a video with a extern recorded gpx. but it can much more:
We cut “Red Light Stops” from the Video and the GPX with “one” click and safe the Vide in ffmpeg copy mode or re-encode it with a xfade.
There is a older Tutorial ( not actual) and in the meantime we added a lot more stuff. Its supported by Kinomal and they add a Mapillary-Feature to rebuild missing gpx parts.
i think it can help your users too.
There is acual the dev_3.29 on github which runs on linux and windows.
