split dat files from Mavic

marklyn · Nov 30, 2018

I regularly download my flight dat files from my Mavic so they can be uploaded to Airdata in order to have accurate flight info, particularly when RC is lost during the flight.
I've had a couple occasions where a lengthy flight resulted in creating two dat files.
Does anyone know why this happens? Is it because the Mavic reaches a certain file size threshold?
In the past AirData will join the two files together if I ask them but wondering what is causing this and if anyone knows of a utility that can join them.
I don't think AirData will always want to do this forever, they're doing it because they're nice folks but I'd like to find a reason and alternative to join them myself if possible.

DanMan32 · Nov 30, 2018

Quite possibly, particularly if the dat files are at or nearing 4GB.
Fat32 has a file size limit of 4GB.

sar104 · Nov 30, 2018

DanMan32 said:
Quite possibly, particularly if the dat files are at or nearing 4GB.
Fat32 has a file size limit of 4GB.

I've never seen a DAT file over 1 GB, so I doubt that's the cause.

BudWalker · Nov 30, 2018

marklyn said:
I regularly download my flight dat files from my Mavic so they can be uploaded to Airdata in order to have accurate flight info, particularly when RC is lost during the flight.
I've had a couple occasions where a lengthy flight resulted in creating two dat files.
Does anyone know why this happens? Is it because the Mavic reaches a certain file size threshold?
In the past AirData will join the two files together if I ask them but wondering what is causing this and if anyone knows of a utility that can join them.
I don't think AirData will always want to do this forever, they're doing it because they're nice folks but I'd like to find a reason and alternative to join them myself if possible.

AFAIK all the DJI platforms will start a new .DAT when the present .DAT size exceeds a threshold. The threshold is different depending on the platform - it's 300 MB for the P3. I forgot which but for one of the platforms the threshold is 450 MB.

I merge .DATs by using the linux cat (for concatenate) command like this
%cat FLY001.DAT FLY002.DAT > FLYmerge.DAT

I haven't tried it but you might try the method shown here
Concatenate multiple files with Windows command line

DanMan32 · Dec 2, 2018

Anyone notice that the DAT file naming scheme on the mobile device has a screwy timestamp? Instead of 24 hour format, it uses 12 hour format but without indicating AM or PM so if you start in the early afternoon, it will go from 12 to 01 rather than from 12 to 13. This causes a sort problem when the file date is messed up due to copying, and you have to sort by filename.

For example, my session on 11/25 generated 7 DAT files, FLY suffix numbers 051-054. 054 shows first because it has the file name 18-11-25-01-02-46_FLY054.DAT
The next one is 18-25-12-11-12_FLY051.DAT.

Also has anyone noticed that the latest GO app version doesn't properly play flight logs (which I believe uses the TXT files) if the app crashed mid-flight? The TXT files are there for the beginning and end of the flight, but the player and log list seems to ignore the TXT files generated before the crash. It used to be that it would still show the entire flight path. It would just interpolate the flight track between the time the app crashed and when it was restarted.