Understanding the GCP editor

Hi All,

I’ve downloaded and got WebODM up and running, and I can see it is doing a very nice job of interpreting and stitching my pics. If I view the textured 3D model in orthographic camera mode, I can see a nice high resolution result that is exactly what I want in the orthophoto.

However, I cannot seem to achieve the same resolution in the orthophoto - it always seems to be much lower resolution. Adjusting the resolution setting sometimes helps a little, but not anywhere close to the 3d model.

I am guessing that the cause may be that I have not georeferenced my pictures. So, I have tried the “GCP interface” - but I can’t get my head round how it is supposed to work.

I load the pictures in, and I start by clicking “add”. I position this on the image, and drag the marker on the map to the same place. Then I select it on the map and click “lock”.

First issue: I cannot add a second pair - if I click “add” again, I only get a new marker on the image, or on the map - I don’t understand how to associate further points.

Then after adding a number of points to various images I try to export a GCP control file. I get the following error message:

A ground control point file should have a minimum of 15 points. There needs to be 5 control objects and each control object must have 3 image points referenced. Please see this article for more information.

It’s recommended to have at least 10 image points.

Seems you have enough image points but not enough control objects. There should be at least 5.

In the “copy n paste” section below, I can see the following - it always only shows one of the points:

+proj=utm +zone=29 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
597928.20 6353272.66 0 3226.00 166.00 image000001.jpg.jpg

Can anyone point me in the right direction?



1 Like

Hey @Brutha :hand: have you checked https://github.com/uav4geo/GCPEditorPro?

Thanks Piero - yes, I did look at it in fact - but since this is only something to play around with, I’m not looking for commercial software with a license fee.

And I will only ever do small projects with small numbers of images - so I’d rather just figure out how to use the standard editor.

Thanks for the info though!



For anyone finding this later: I think I get it! After adding a point on the image, you then need to either select an existing control point on the map, then click your image point again, or add a point to the map, then click your image point again (sometimes it seemed to automatically link them).

Anyway, clicking a point on the map then a point on the image links them - lets see if the results work correctly!