Home        Store        Learn        Blog

Read, export and understand Telemetry data: COMPASS degree?

HI
i’m using qgroundcontrol for the Bluerov2, after each session I have a TLOG files with telemetry,

when I use qgroundcontrol or missionplanner to read the TLOG file I was able to see COMPASS degree (in this image 182°)
buss
when I try to export data from TLOG file using missionplanner I can save it as TXT and then I was able to read it.

but where are compass data??? I found only the value of compass_variation but I can’t understand it… this value is degree? radian?

for example:
Line 801: 02/02/2018 11:09:12 FE 16 0 0 F 1 1 C1 mavlink_ekf_status_report_t velocity_variance 0 pos_horiz_variance 0,01023314 pos_vert_variance 0,0003417233 compass_variance 0,02745412 terrain_alt_variance 0,0006562088 flags 485 sig Len 30
or
Line 802: 02/02/2018 11:09:13 FE 16 0 0 22 1 1 C1 mavlink_ekf_status_report_t velocity_variance 0 pos_horiz_variance 0,01017215 pos_vert_variance 0,008389785 compass_variance 0,02903016 terrain_alt_variance 0,0005503477 flags 485 sig Len 30

here the complete TLOG file (3MB) if someone could help me. download TLOG file 3MB
thanks
Mauro

QGC shows a clockwise positive angle (0 → 360º).
image

MavLink sends the angle between -pi and +pi, where the positive angle is the clockwise direction and zero is north.

+------------+-----------------------+----------------+----------------+------------------+--------------------+---------------------+-------------------+--+---------------------+--------------------+
|  timestamp | ATTITUDE.time_boot_ms |  ATTITUDE.roll | ATTITUDE.pitch | **ATTITUDE.yaw** | ATTITUDE.rollspeed | ATTITUDE.pitchspeed | ATTITUDE.yawspeed |  | yaw (grad -180|180) | yaw (grad 0 | 360) |
+------------+-----------------------+----------------+----------------+------------------+--------------------+---------------------+-------------------+--+---------------------+--------------------+
| 1517566176 |         292507        | -0.03405671939 | 0.09500097483  | **-3.108595848** | 0.002565450035     | -0.003794062883     | -0.02150129899    |  | -178.1146754        | 181.8853246        |
+------------+-----------------------+----------------+----------------+------------------+--------------------+---------------------+-------------------+--+---------------------+--------------------+

To generate a csv from tlog, you can check Mavgen.py to translate, but how?

thank you Patrick,
you say that MavLink sends angle

but I don’t understand where it is.

sorry I know that I’m very newby but:
I have to read the tlog file or I have to generate (or read) another type of file?

thank you so much
Mauro

The tlog data is stored in binary format, not for human read. You need to transform the tlog in something else, like a csv.

thank you Patrick,
of course I have used missionplanner to save it as TXT,
my question was,
in this TXT files txt file download
where are the compass information?

Looks like “yaw” first appears on line 724 of your text file:

1 Like

The messages, and their contents are documented in large part here and a few less common ones here. The message @paul-unterweiser shows gives you heading in radians, VFR_HUD gives you heading in degrees.

1 Like

thank you so much!!! now I can see it
:smiley::smiley::smiley::smiley::smiley: