Survey (Grid) - can't get sufficient forward overlap with DO_DIGICAM_CONTROL

Hi All,

I was wondering if someone would be able to shed some light on this issue.

We have an X8 copter and are trying to fly very accurate (RTK GPS) low altitude (~5m) small scale missions planned using Auto WP > Survey (Grid) with very high side and forward overlap. The side overlap is no problem, but we’re unable to achieve sufficient forward overlap (80%) using DO_DIGICAM_CONTROL, as Mission Planner seems to limit triggers to a separation of no less than 4m (when travelling along each flight line). At this altitude, we require triggers to be under 1m apart.

When increasing the forward overlap %, the “dist between images” value decreases as expected to less than 4m, but the trigger points on the map are never closer than 4m, and as a result we don’t get enough forward overlap.

I found this post Photo numbers in survey grid but not sure if it’s still relevant as we can get spacing less than 10m, just not 4m?

Ideally we’d like to be able to capture an image every ~25cm along a flight line. We’ve tried CAM_TRIGG_DIST as well, but it appears to be limited to a minimum distance of 1m. If anyone could shed some light on how to overcome this it would be much appreciated.

Using Mission Planner 1.3.59 and 3.5.7 X8 octocopter, and a very low res camera hence the need for low altitude.

Many thanks in advance.

yes, there is a hard coded limit of 4m at the moment
I will make a change in beta to change this to 0.1m


also just be aware there is a wp limit depending on your hardware.

Hi Michael,

Many thanks for your quick reply, much appreciated. It would be great to have this feature in the next beta!

In the meantime, we will use CAM_TRIGG_DIST. Is it true that the minimum distance between triggers using this method is 1m? We have tried setting CAM_TRIGG_DIST to less than this, but triggers still seem to occur every 1m.

Also, we’ve found some conflicting or possibly out of date info on the max number of waypoints our Pixhawk2 will handle - is the 724 from this post still correct?

Many thanks again.