Help needed linking phantom 4 to Reach for accurate gps coordinates

I would like help to link my DJI phantom 4 to a reach RTK . I am wiling to pay for the help
My e-mail is I am located in Massachusetts USA.
I fly the drone with autopilot and use it for photorammetry. I want to improve the accuracy of the GPS coordinates as photos are taken. After flying the mission I want to download a file of the coordinates so that I can merge them with the data attached to the photos. I want to accuratly identify ground control targets and draw contour lines of the site
Contact me if you can help.


Rather than modifying the Phantom, why not use the reach to establish ground control positions accurately? Regardless of the Phantom having accurate positions you’ll still require some (1 or more) ground control points to prove the accuracy of your overall model and survey. If your site is small it would be just as simple.

Without any active ground control you would have no way to determine the validity of the survey completed with the reach regardless. ie - ruling out “false” fixes, wrong base coordinates, etc, etc.

We deploy a Trimble UX5HP and still use ground control points as a check for all of our site surveys - this is common practice.

If it is absolutely necessary to connect it to the Reach you’ll have to disassemble the Phantom 4 (voiding warranty) and figure out how the camera is triggered and connect that and the ground to the Trigger pin on the reach. Another problem with the Phantom Series pre-builds are that they’re very picky about weight and distribution, configuring the antenna, reach and battery (if you don’t utilize the Phantoms power) would require a lot of testing.

Thank you Nicholas, I think you’re saying that if I map the coordinates of my ground controls with the Reach or some other rtk device like the dual channel Pixi then I could somehow get a coordinate file out of the rtk device and import that into my photogrammetry software. Then to verify the locations of those coordinates on my site photos that display the ground controls I would be scaling the photo image over the imported coordinates. Yes my sites are small. 2 to 5 acres.

If that the correct strategy then would you be able to help me do it? I am a builder , not and engineer or surveyor. I am doing this out of frustration at the 6 month plus delays I have to deal with for surveys and site topography for house placement and septic designs.

I would need help to put such simplified system together and as I mentioned before I am willing to pay for such help.
My e-mail address is if you would like to talk direct with me.



You could use the Reach to Survey the GCPs (Ground Control Points) - It functions as an RTK GPS with CM accuracy.

Most photogrammetry suites offer the use of coordinate systems and GCPs. I personally use Agisoft for my processing needs - it’s cost effective. The convenient part of the Phantom is it operates in WGS84, the same as the Reach - this would avoid coordinate transformations prior to aligning photos or selecting your GCPs.

There are several methods of performing the actual survey with the reach, multiple pieces of software and methodologies. The method you use will depend on your distance from your base typically - if you have long baselines you may require long single point observation times over each point. This can easily be done by recording the time spent over each of the ground control points and post processing each of the points based on time as a single observation in RTKPOST. In your case that may be the easiest method to use.

I would read through the Reach Documentation and check out the forum, there are various posts on surveying and the general use of the Reach.

I Would Start Here:
Reach for Land Surveying
Reach Documentation

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Thank you for taking the time to reply Nicholas. I will follow through on the links. I am very green at this and have a lot to learn.


Hey Gordon,
Did you nail this?
You can do it many ways.

strap a reach onto the DJI and then post mission process for RTK and then use exiftool or digikam to redo the gps in the photos.

go to a few points on the ground that you can identify from your photos (after the drone flight) and position them accurately with either emlid reach or piksi or any other rtk.

go out prior to the drone flight and put down placards that you can recognise from the air and position them with RTK.

I can help you develop a simple workflow using open source tools, but maybe not in an online forum. Please send me an email at and we can talk.