Support of GPS setpoints in OFFBOARD mode

[mzahana]

Hi. I would like to know if I can send GPS setpoint to PX4 in offboard mode. One work around that I know is to to do some transofrmation to transform the difference between current gps point and target point to a local_ned position setpoint which px4 accepts. However, it would be more convenient to have this directly implemented in px4 firmware.

If not currently implemented, where should it be implemented ? Maybe I can give it a try. Also, a corresponding mavlink msg would be required, right?

Thanks.

[TSC21]

@mzahana PX4 is currently working torwards having navigation on the local frame only, meaning there is going to be always a correspondence/transformation between global and local frames on the Firmware side. If you are using MAVROS, maybe you will want to try fake_gps plugin, which transforms GPS into local coordinates already before sending the setpoint msg to the target FCU. It considers as the local origin the Home Position.

[TSC21]

In any case the support you are talking about is also possible by adding an handler for SET_POSITION_TARGET_GLOBAL_INT and then the respective usage on the the Firmware.

[mzahana]

Thanks for the response. The idea is to have the option to send GPS setpoints in outdoor setup with available GPS sensor. The fake_gps plugin in mavros, https://github.com/mavlink/mavros/blob/master/mavros_extras/src/plugins/fake_gps.cpp , does not send setpoints. It basically sends faked gps data out of mocap or vision estimates, hence the name fake_gps.

However, what you suggested in the second reply makes more sense.

There are two possible ways to solve this. 1) making a mavros plugin which takes gps setpoints and convert it to local frame setpoints. Then, sends it to px4. This is easy to do, but will only work with through mavros.

2) introducing a new setpoint type (e.g. setpoint_gps) with corresponding maks type and implementation on px4 firmware. This is more complex than first option, but not restricted to mavros.

On Jul 7, 2017 10:36 PM, "Nuno Marques" notifications@github.com wrote:

In any case the support you are talking about is also possible by adding an handler for SET_POSITION_TARGET_GLOBAL_INT http://mavlink.org/messages/common#SET_POSITION_TARGET_GLOBAL_INT and then the respective usage on the the Firmware.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/PX4/Firmware/issues/7552#issuecomment-313773820, or mute the thread https://github.com/notifications/unsubscribe-auth/AIZT6wzQOktDmR_qLrq-1dDd3E4F6onVks5sLoi_gaJpZM4ORT7D .

[TSC21]

You don't need to create a new msg as the one I told you is enough. fake_gps fits another purpose, you are right, I just wasn't sure what was the source of the data. But a new plugin called setpoint_global would make sense, considering that it receives lla data (geographic_msgs can handle data perfectly) and then do the conversion as it is done on fake_gps (LLA->ECEF->ENU->NED). You are welcomed to add the support and will gladly review it. The same thing if you bet on support global setpoint on the FCU side, but you should consider add that support for the global_to_local branch.

[mzahana]

I will start with the Mavros option as I had that implemented and tested in flight some time ago. Then, probably later I will look into the FCU implementation.

[TSC21]

I will start with the Mavros option as I had that implemented and tested in flight some time ago. Then, probably later I will look into the FCU implementation.

Great. Have a look at fake_gps so to know what functions you can use to apply the transform LLA->ECEF->ENU.

[TSC21]

@mzahana done any progress in this?

[mzahana]

Will send a PR over the next week.

On Jul 27, 2017 6:09 PM, "Nuno Marques" notifications@github.com wrote:

@mzahana https://github.com/mzahana done any progress in this?

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/PX4/Firmware/issues/7552#issuecomment-318391336, or mute the thread https://github.com/notifications/unsubscribe-auth/AIZT605pI8AYnh089XP3HizZ_lsWjN6Rks5sSKg6gaJpZM4ORT7D .

[mzahana]

I created a mavros plugin in https://github.com/mavlink/mavros/pull/764

[TSC21]

@mzahana we need an update on the PR so it can be merged. Thank you

[mzahana]

Now, using https://github.com/mavlink/mavros/pull/764 (already merged into mavros master), GPS setpoints can be sent via MAVROS.