[GRASS-user] Orthorectification without GCPs

Stefan Blumentrath Stefan.Blumentrath at nina.no
Fri Apr 16 06:01:28 PDT 2021

Hei Dugal,

g.gui.image2target generates the "CONTROL_POINTS" file (I guess in the folder of the image group).
If you want to skip g.gui.image2target, you have to create that file a different way.

Here is one possible way:
Just create a random list of GCPs in g.gui.image2target to see how the file should look like and then re-create it with the GCPs you have (e.g. in a script or however your workflow is).


From: grass-user <grass-user-bounces at lists.osgeo.org> On Behalf Of Dugal Harris
Sent: fredag 16. april 2021 12:42
To: grass-user at lists.osgeo.org
Subject: [GRASS-user] Orthorectification without GCPs

Good day

I wonder if anyone could help with this...  I am new to GRASS and am trying to orthorectify aerial images.  I have accurate camera exterior orientations already, so want to skip the manual g.gui.image2target step in https://grass.osgeo.org/grass78/manuals/i.ortho.photo.html<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgrass.osgeo.org%2Fgrass78%2Fmanuals%2Fi.ortho.photo.html&data=04%7C01%7C%7Cca2636775ccc4376985608d900c45023%7C6cef373021314901831055b3abf02c73%7C0%7C0%7C637541665708352737%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=15nnQq5kaVnA7%2FiQoGrcF%2F4qf1jOuJnxeYJpuES%2BZE0%3D&reserved=0>, and just apply the exterior orientation as is.  Is this possible?

If I run i.ortho.rectify without that step, I get:
WARNING: Unable to find file [CONTROL_POINTS] of group [3318D_2016_1143_07_0315_RGB_NoRotate at NGI_3318DD_Ortho_Test in NGI_3318DD_Ortho_Test]
WARNING: unable to open control point (Z) file for group [3318D_2016_1143_07_0315_RGB_NoRotate at NGI_3318DD_Ortho_Test in NGI_3318DD_Ortho_Test]

Thank you

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