Idea for Phantom 4 pro & Reach M+ = no GCPs

DJI GS Pro supports a stop-and-shoot mode for capturing images. It’s limited to 99 shots per mission.

What if you attached a Reach M+, antenna, and small battery to the P4P. Log all the Reach M+ data for PPK. The image timestamps, in part because they were captured while the drone was stopped, could be used to coordinate the drone’s exact position without the need to synchronize image capture with the M+.

Perhaps a low cost solution for GCPless photogrammetry via a P4P.


I may try it.


Lol, that is a really brand new idea ! Could you develop a little ?

I see a potential nightmare to identify the exact plot in the cluster jungle.
1.Run at 1hz with fewer plot to choose from but then again not the exact coordinates is picked due to slow update rate and to much movement
2. At 14hz you have alot to choose from but they are spread all over a 1x1m ish area, which one to choose?

Edit. but triggersolution that timestamps reach with coordinates might be doable, not that accurate

As an experiment, I just took two photos from my P4P of my ipad running an NTP client. The P4P had GPS lock, and I assumed its internal clock is set from GPS? I think not now. The delta between the time displayed on the iPad vs what’s recorded in exif is 157 seconds. So it appears the P4P’s clock is a couple of minutes off. Good news, both a RAW and a JPEG were within a second of each other (158 and 157 seconds).

Anyone know how/when the P4P sets its clock?

Alternatively strap a MAPIR camera and reach module to the back of the drone , use the Reach to trigger the MAPIR and feed it Nav DATA, this is my next project once I have my Lora radio working with the Reach RTK module…

I’ve done more testing. I suspect my earlier results were due to not waiting long enough before taking timing photos with the drone. I constructed a test rig that holds a digital watch within the frame of the P4P’s camera. Unlike what I’ve read elsewhere, the EXIF date/time information seems to be accurate within a second of GPS time. Here’s a link to my test setup and results:

With PPK, flying at 2m/s, that would reduce the camera location error from about 5 meters to less than 2. If the drone paused for two seconds, I suspect you’d nail it.

I had another thought. DJI’s Ground Station Pro allows you to “Capture at Equal Time Interval”. If the API it’s using schedules photos to be taken on at second granularity, then the EXIF date&time might be dead on. This would be much faster than the stop-n-shoot mode I’m using now.

My P4P is out for gimbal repairs, so testing is at least a week away.

I’ve gotten my kit down to 135 grams.

Remember that strapning gear into the Phantom will affects its performance, tuning, flight time etc.

if you want the centimeter performance I would suggest to build your own. That way you can get RTK for your navigation of the drone, using the reach m!

This topic was automatically closed 100 days after the last reply. New replies are no longer allowed.