This video shows how to configure Mission Planner parameters in conjunction with an Autopilot controlled mapping camera trigger. The trigger method for APM requires a USB cable and either an EFL600 LED light controller or HK 5V LED light switch. The trigger method for PixHawk also requires a USB cable and one of the aforementioned LED light controllers as well as a 5V step up board since PixHawk only puts out 3V from its RC outs and CHDK needs 5V to utilize the remote trigger function.
Both of the setups shown in this video allow the cam_trig_dist parameter to trigger a Canon mapping camera with CHDK based on distance traveled in flight and therefore get consistent overlap in aerial imagery. This is optimal for mapping.
PixHawk and APM Mapping Camera Configuration