RFC-0019 Precision Target MAV_SYS_STATUS extension

[dakejahl]

This would also support status reporting for PRECISION_HOLD
mavlink/mavlink#1858

[dakejahl]

Further thoughts on how the MAV_SYS_STATUS bitfields are populated

present
There are two cases

1. Flight controller precision targeting system (eg IRLock). The autopilot can determine if the driver is running and healthy.
2. Offboard companion computer solution via LANDING_TARGET. We should probably expect a HEARTBEAT message since the LANDING_TARGET protocol implies that the LANDING_TARGET message is only sent when a target is visible. This means we also probably need a component ID definition MAV_COMP_ID_PRECISION_TARGETING

enabled
The precision maneuver is actively engaged. This can be determined within the autopilot software from the mode/submode of the control and navigation implementation.

healthy
The precision targeting system can actively see a target. For the autopilot managed implementation, we can look at internal data (eg px4 uorb) and monitor with a timeout. For on offboard companion computer implementation we can monitor for the LANDING_TARGET message with a timeout.

[dakejahl]

@akkawimo

[hamishwillee]

I see what you're doing with MAV_SYS_STATUS_SENSOR_XY_POSITION_CONTROL below, but what's the proposal for MAV_SYS_STATUS_SENSOR_PRECISION_TARGETTING (I might be missing something obvious)

[hamishwillee]

@dakejahl Note, not sure how you want me to progress this. But I'll keep an eye out for your comments.

[dakejahl]

The proposal is to just add this new flag MAV_SYS_STATUS_SENSOR_PRECISION_TARGETTING since "XY position control" isn't really accurate -- to me "xy position control" makes me think of an optical flow or VIO system. There are already flags for vision and optical flow tho... just seems like a lot of these flags are unused and not well thought out in the first place. A flag that clearly says "precision targetting" in the name seems more appropriate, and would probably be acceptable (in terms of language) to both px4/ardu peeps