Umark / unlink GCP from image

If I incorrectly mark a GCP in an image, which I then discover does not actually show in that image (I picked the wrong GCP in the image), how do unlink that image from that GCP?


Hi Caleb,

We would suggest the following:

  1. In the rayCloud, select the GCP being marked in the wrong image.
  2. On the right sidebar, you should be able to see the image thumbnails where the GCP are marked or where the software estimates the point to be. Hover the mouse over the image being wrongly marked and press the Delete from the keyboard.
  3. Click Apply in the section Selection above the image thumbnails.
  4. On the Menu bar, click Process > Reoptimize. This way the reconstruction of the model will take the change into account.


Thanks, so easy, but I could not find where this is documented.


This might be the article you were looking for:

Glad we could help.


Struggled with this so much too. I discovered after serious field costs that you never place a GCP under hanging power cables or near any post for that matter. When it comes to pixels, the model formation will struggle with similar looking but high hanging pixels. Thanks Julie for this educative little but crucial piece.


Regards, Paul, GA Ltd

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I can’t seem to be able to delete the images with wrong marked GCPs with this procedure. Nothing happens when I hover on the thumbnail (becomes with orange square around) and press DELETE.
Any idea what I do wrong?


Hi @r.gadbois-langevin ,

May I ask which version of Pi4Dmapper are you using? Are you in the Discovery mode? Is the logo green or gray?


I also have a problem where gcp have marked incorrectly. When I follow the steps above to delete the imaged nothing happens. I am using version 4.7.5