Using Drone2Map with ONLY ground control points (no GPS)

[KathrynCatlin2]

I have a series of photos that were taken with a camera with no onboard GPS. Instead, we mark ground control points and record their location with a cm-accurate TotalStation, which are then matched up with the photos to produce a high-accuracy orthomosiac & DEM. TotalStation points are usually more accurate than a drone GPS for our application (archaeology).  I usually process data like this in Agisoft Metashape, where it is easy to tell the software to ignore the GPS data and only use the imported GCP locations.  I'd like to replicate this process in Drone2Map, but I have been unable to figure out how to use Drone2Map with images that lack inherent GPS coordinates.  Is it at all possible to do this in Drone2Map or am I out of luck?  Thanks for any help. 

[CodyBenkelman]

Kathryn

You're correct that your TotalStation control points will be more accurate than a drone's GPS points, but accuracy is only part of the question.  without any relative positioning information, the software won't know if image 77 is north, south, east, or west of image 76. 

I haven't actually tested this but you should be able to proceed if you're willing to build a simple table with estimated camera positions - e.g. filename with path, longitude, latitude, altitude (above sea level) should be enough - but that might be a bit tedious.  You can calculate intermediate photo positions if you can estimate start and end positions for the first and last image and the spacing between flightlines.  

As noted I haven't tested this so I'm not sure if you can make it work without creating that table.  If you can get the project started, you should get good accuracy with your control points.

The other question is camera - will your camera be in our drone camera database?  

https://doc.arcgis.com/en/drone2map/latest/help/edit-camera.htm

Cody B.

[KathrynCatlin2]

Hi Cody,

Thanks for your answer.  It sounds like Drone2Map won't be appropriate for this application, unfortunately.  We use just a small point-and-shoot Nikon attached to the end of a long pole that we carry across the site, so I doubt it is in your database, and each run of images can have 100 or more photos in it which may not be in an easily-reconstructed "flight plan." Building a table post-hoc for each run is probably too time-consuming.  We will just continue to use Metashape, which can do this natively/automatically!

Kathryn