GPS data issue: exiftool gives wrong values

[cjfontec]

Hi, I am working with a Transcend Dashcam DrivePro 250.
I tried to extract the gps data from a MOV file in order to have a json to work with.
exciftool successfully extracts the data, but the resulting GPS is wrong. Using DrivePro Toolbox (an app from transcend) I see the correct GPS (which also is shown in the video itself).
as an example, exiftool gives the following:

Code Select Expand

Type='gps ', Sample 106 of 106 (32768 bytes)
17dc8750: 00 00 80 00 66 72 65 65 47 50 53 20 a0 00 00 00 [....freeGPS ....]
17dc8760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [................]
17dc8770: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [................]
17dc8780: 15 00 00 00 0c 00 00 00 2e 00 00 00 15 00 00 00 [................]
17dc8790: 07 00 00 00 02 00 00 00 41 53 57 00 9e ae 81 45 [........ASW....E]
    [snip 32688 bytes]
GPSLatitude = 40.1695475260417
GPSLongitude = 72.4883138020833

while in the frame it says W73 30.07 S41 49.82.

Any idea how to solve this?
thanks!

[StarGeek]

Can you make a short sample available so Phil can take a look and possibly add it.

[cjfontec]

how can I trim a video without losing the metadata? vlc and ffmpeg remove the gps info. the smaller video I have is 50 MB in size.

EDIT: i uploaded a video to s3 and generated a link that last for two days, will that be enough? https://bit.ly/3Jwih2c

[Phil Harvey]

Code Select Expand

> exiftool ~/Desktop/test_video.mp4 -ee -warning
Warning                         : GPSLatitude/Longitude encryption is not yet known, so these will be wrong


[azimrahd]

Hi, I am also trying to extract gps data from Transcend drivepro dashcam, and the data is totally different from what's displayed in the video.

[StarGeek]

From the post directly above yours

Warning                         : GPSLatitude/Longitude encryption is not yet known, so these will be wrong

[RodneyGobbler]

I'm having the same issue with a Campark dashcam, video maybe found at https://img.gg/T8ZSd9d.

Its saying GPSLatitude/Longitude encryption is not yet known, so these will be wrong
Campark dashcam not able to understand GPS data something with Docxx: framenumber not defined.

Any idea to fix this?

[Phil Harvey]

Hi Rodney,

Unfortunately I haven't yet been able to determine the algorithm that is being used to obfuscate the GPS coordinates in these types of files.  I'm hoping that someone else will be able to solve this puzzle and post a solution because I don't have the time needed to be able to do this myself.

- Phil