Deciphering my dashcams gps log

Woden · 16 Jun 2020 at 12:36

So I installed a dashcam (Halfords HDC400, £119 front back and memory card, cant grumble), and got all excited when I saw the camera saves a gps log file every day with where i have been. But, it is in a really, really weird format I cant decipher, with no headers.

Code:

A20200615115214000,5332.074219,N,208.987991,W,4.3,8.4,115.4

Any ideas? I thought it could be a neat little python project tying that data into google maps or something. But I am stumped with how to pull my co-ordinates.

First bit is clearly date and time, but I don't recognsie the format
2nd bit is a coordinate, in a weird layout. That isn't where i live but close, and my house is at 53.33° N
Then its obviously the other coordinate, but I don't get it, +/- 0.20° is no where near where i have been.
No idea what the last three numbers are.

SupraWez · 16 Jun 2020 at 13:33

Its not far off an NMEA GPRMC message, maybe custom format, do they offer any software to process the log?

Mcnumpty2323 · 16 Jun 2020 at 13:42

should be a hdc app
that lets you show gps location on the videos
though no idea if like my nextbase cam you can also view
it on google maps

visibleman · 16 Jun 2020 at 18:45

It's a bit of an odd format but i believe for location work on the basis of dddmm.mmm (degrees and minutes; work right to left) and take note of the polarity, i.e - N & E are positive, S & W negative (IIRC). And to convert to decimal, use -

Code:

decimal = degrees + (minutes / 60)

So your latitude would be -

Code:

53 + (32.074219 / 60) = 53.5345703166667

And i'll let you work out the longitude, just note that it's a negative number.

Regarding the entire format (could be completely wrong on this) - no idea on initially character, probably GPS lock or tracking status; then it's date and time (YYYYMMDDHHMMSS???); lat and long with polarity; then it's probably speed in knots (typical in NAV/GPS data); and most likely acceleration (m/s²) in two directions.

A crude string manipulation lat/lon converter in PHP - http://sandbox.onlinephpfunctions.com/code/b83011a896f454ed484e3021e2e33362dc81552e

Woden · 17 Jun 2020 at 11:23

Mcnumpty2323 said:
should be a hdc app
that lets you show gps location on the videos
though no idea if like my nextbase cam you can also view
it on google maps

The myHDC app is pretty good really, especially for a budget camera. Does show me GPS location and shows a trace on Google maps.

visibleman said:
It's a bit of an odd format but i believe for location work on the basis of dddmm.mmm (degrees and minutes; work right to left) and take note of the polarity, i.e - N & E are positive, S & W negative (IIRC). And to convert to decimal, use -

Code:

decimal = degrees + (minutes / 60)

So your latitude would be -

Code:

53 + (32.074219 / 60) = 53.5345703166667

And i'll let you work out the longitude, just note that it's a negative number.

Regarding the entire format (could be completely wrong on this) - no idea on initially character, probably GPS lock or tracking status; then it's date and time (YYYYMMDDHHMMSS???); lat and long with polarity; then it's probably speed in knots (typical in NAV/GPS data); and most likely acceleration (m/s²) in two directions.

A crude string manipulation lat/lon converter in PHP - http://sandbox.onlinephpfunctions.com/code/b83011a896f454ed484e3021e2e33362dc81552e

This is amazing, thank you! Neat little project when things calm down at work and I can have my weekends back.