[Bug] Incorrect ADSB Heading

[qtweng]

Describe the bug

ADSB heading angle handling is incorrect. Transponder report message reference states heading is [-pi, pi] where 0 is north.
Currently, the driver code adds pi to the heading angle before wrapping to pi causing 0 heading to be south in the uorb message. This is reconciled in adsb conflict handling by adding 180 deg and in adsb vehicle mavlink msg by adding pi.

To Reproduce

1. Flash drone with transponder report enabled in dds_topics.yaml
2. Prepare drone with adsb receiver
3. Connect companion computer through uxrce
4. Observe angle difference between qgroundcontrol GUI and TransponderReport message

Expected behavior

When obtaining heading from ADSB, heading should be 0 when vehicle is pointing north.

Screenshot / Media

No response

Flight Log

No response

Software Version

1.15.2

Flight controller

Cube Orange Plus

Vehicle type

Fixed Wing

How are the different components wired up (including port information)

No response

Additional context

No response

[qtweng]

I can implement a quick fix once this is sanity checked and verified, and if no other use of ADSB heading angles other than the ones listed are present.

[dakejahl]

I wouldn't be surprised if there's a bug. Can you open a PR with a fix and share the relevant evidence of the error? Maybe you can share a screenshot of QGC, where the ADSB indicator is visible on the map view and the adsb.heading is visible in the Telemetry card, so we can clearly see the value doesn't match the position in the map view.

[slgrobotics]

@sfuhrer @dakejahl - I don't think there's a bug, but msg/TransponderReport.msg wrongly states that:

float32 heading 	# Course over ground in radians, -pi to +pi, 0 is north

It should be:

float32 heading 	# Course over ground in radians, 0 to 2pi, 0 is north

When filling this field, do something like this:

.heading = wrap_2pi(_location_metrics.gps_cog_rad), // Course over ground in radians, 0..2pi, 0 is north

My code here: https://github.com/slgrobotics/PX4-Autopilot/blob/dev/src/modules/rover_lawnmower/LawnmowerControls/Publish.cpp

build it like this: make px4_sitl gz_lawnmower

Here I use ADS-B to view GPS data in relation to EKF location which is reported to QGC:

Screencast.from.2025-06-26.13-36-21.mp4

Here is Discord discussion about it: https://discord.com/channels/1022170275984457759/1387464400352444597

[dakejahl]

@slgrobotics can you please open a PR to fix?

[slgrobotics]

I sure can, who's going to merge it?