We need a TRIGGER command for fixed wing aerial photography/survey work.
The current method of camera shutter control is start/stop only. (DO_REPEAT_RELAY, DO_REPEAT_SERVO don't work.)
Start/stop control only works if the camera has an intervalometer mode.
Start/stop shutter control makes geo referencing hit or miss at best.
There is no feedback during the flight that the shutter has been operated.
For fixed wing aerial photography/survey work we also need a stabile platform to assure the proper orthographic pointing of the camera. Joystick control could point the camera off axis if needed.
A camera platform capability is available with the released ArduCopter firmware but not for the ArduPlane. ArduCopter also needs a TRIGGER command.
The trigger event should be recorded by the internal log file so it can be directly associated with the GPS position, time, and airframe attitude for accurate geopositioning.
The Mission Planner should log the event and the event should be downloaded as part of the data stream. There could be a flash or marker on the Flight Data path display and a verbal announcement of the occurrence.
A trigger could be used to snap a camera shutter, start/stop a movie recording, drop a water bottle or marker, pop a parachute in an emergency, etc.
The trigger should be able to be fired from the ground by the user (via the Mission Planner) or by the APM's WP file at timed or distance intervals between designated waypoints.
Here are some suggested programmable attributes of the TRIGGER:
1) Trigger mechanism:
If actuation is by a servo - set the servo port number.
If actuation is by a relay - set relay reference.
If actuation is by a logic level - set output reference.
The duration of the trigger in milliseconds.
Choose time in sec. or distance in Meters
The TRIGGER and Stable Platform attributes could be defined by the Mission Planner on the Configuration page. Maybe added selections after Antenna Tracker.
The trigger actuation could be set by the Mission Planner - Flight Planner on the Waypoints Command Line.
I have more specific suggestions for the trigger parameters and command line definitions.