Author Topic: Inverse geotagging from NextBase dashcam footage  (Read 3404 times)

Phil Harvey

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #15 on: October 09, 2018, 09:32:56 AM »
North should be 0 if this is compass data.  I thought about direction, but it didn't make sense because you made some 90 degree turns and I don't see changes in this number that reflect this.

Also, is this local time or UTC?

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

zubairlk

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #16 on: October 09, 2018, 09:42:11 AM »

Also, does the video start at 06:42 local time, or UTC?

This is from the UK so local time is the same as UTC.
The actual time of footage was 07:42 cause of daylight saving.
But the camera hasn't picked that from the GPS and remains at GMT +0.

Regards
ZubairLK

Phil Harvey

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #17 on: October 09, 2018, 09:43:54 AM »
Thanks.  I'll just assume UTC and add "Z" to the date/time values like I do with the NextBase 512GW (although the 512G format is VERY different!).

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

Phil Harvey

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #18 on: October 09, 2018, 09:56:13 AM »
Actually, I think you are right about the compass data.  Could the signed value be degrees * 100?  (in the range -180 to 180 degrees?)

- Phil

Edit: So is the the direction of the camera, or direction of travel?  (ie. GPSTrack, or GPSImgDirection?)
« Last Edit: October 09, 2018, 10:06:44 AM by Phil Harvey »
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

Phil Harvey

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #19 on: October 09, 2018, 12:28:21 PM »
I've just released ExifTool 11.13 with the assumption that the direction should be extracted as GPSTrack -- please let me know if you discover otherwise.  It should be GPSTrack for the 512GW because it was stored as an NMEA RMC sentence, and the NMEA specification states that this is the track direction.  I'm hoping the 512G is the same (even though it isn't stored as NMEA).

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

zubairlk

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #20 on: October 10, 2018, 03:44:23 AM »
Thank-you so much! I'll check it out over the weekend and let you know.

Regards
ZubairLK

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #21 on: November 12, 2018, 07:53:59 AM »
I just happen to be looking at extracting GPS data from nextbase MOV files.
We have a few threads open on this topic at the dashcamtalk forum, for
example https://dashcamtalk.com/forum/threads/next-base-312-gps-format.29175/#post-440026.

The sggps program mentioned there will decode video written by older firmware,
but Nextbase have changed the way they record GPS under more recent firmware.
It now seems to be straight forward  NMEA. I am exploring the go language which is new to me before writing a version to handle, at least, the Nextbase 312GW output. It looks straightforward.

If you compare the old and new versions of the GPS data with the NMEA spec, it ought to be possible to identify all the fields.

Hope this helps.

Phil Harvey

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #22 on: November 12, 2018, 07:55:50 AM »
As I mentioned earlier, my 512GW sample stores GPS in NMEA format, and ExifTool can decode that.  If you have any samples that don't work with ExifTool, please send them to me.

Thanks.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

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Re: Inverse geotagging from NextBase dashcam footage
« Reply #23 on: March 30, 2019, 05:22:22 PM »
I have at last put my program "mov2gpx" onto github at
github.com/clarified/mov2gps.

It works with Nextbase 312GW and similar cameras. But not (yet) with the other Nextbase models. After it was written, Nextbase sent me samples from their other models that generate MOV rather than mp4. I was surprised that the way that the gps information was recorded was different enough to stop Version1 working. But except for one outlier, it seems to be easy to modify mov2gpx to handle them. That will be Version 2 - but it will have to wait until I have some spare time.

exiftool was useful when writing mov2gpx.