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Read, export and understand Telemetry data: COMPASS degree?


(mauro saccone) #1

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


(Patrick José Pereira) #2

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?


(mauro saccone) #3

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


(Patrick José Pereira) #4

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


(mauro saccone) #5

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?


(undersearobotics.com) #6

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


(Jacob) #7

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.


(mauro saccone) #8

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