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Dataflash log of BlueROV2

I am currently trying to process the BlueROV2’s data flash logs in a proper way. I use QGroundControl as ground station and thanks to mavlogdump.py, logs can be put in .csv format.
The problem is there are many messages I don’t get (FMT, PARM, IMU, IMU2, NKF1, …) and this link Downloading and Analyzing Data Logs in Mission Planner — Dev documentation explicits a few of them.
I’d like to keep only the useful recorded data (velocities, accelerations, pitches, rolls, battery info, etc…) but I can’t manage to find a documentation which lists all of these.

My question is What to keep? What to delete?
I saw there were “IMU” and “IMU2” for example, this means there are several IMU in the BlueROV2 ? Where are they ?
Some parameters won’t show any information, for example “BAR2” without any description of what it is
There are several parameters in which I can find Roll, Pitch, Yaw but which one is trustworthy ?
The timestamp in the log is said to be in microseconds following the unix epoch, I was wondering, why is this time reference chosen ? (Simple curiosity)

My apologies for any poor phrasing, I am still a student and new to this field


There’s a better explanation of what each messages logs here.

Yes, most flight controllers have multiple IMUs for redundancy.

That depends a bit on what you are interested in…
IMU is likely not relevant unless you care about gyro/accelerometer/vibrations, for example.

I’m just guessing here, but I think it was because it is a standard, and one easy enough to implement and use.

Hi @Nathan_R07, welcome to the forum :slight_smile:

Willian has mostly answered the questions you asked, but it may also be useful to discuss what you’re actually trying to achieve. Our documentation (and the discussion on this forum) tend to be more focused around MAVLink messages and the tlog files they’re recorded in by QGroundControl.

If you’re trying to visualise data over time then both dataflash logs and telemetry logs should work fine in programs like the Log Viewer.

If you’re doing some kind of data alignment and/or programmatic analysis it may be easiest to use the telemetry logs, with something like this Python code. I don’t have much experience with dataflash logs, although I believe they store more frequent measurements than tlogs, but that can be more information than is desired/useful.