[GRASS-user] Auto-detection of GCP for rectifying image

[Johannes Radinger]

Hi GRASS users!

I have an image of a small object (e.g. photograph of blue square 15x5cm)
which I want to automatically georeference. In addition, the image contains
6 points where I know the exact coordinates, i.e. these points can be use
as ground control points (GCP) for rectifying the image. This is basically
a experimental setup, and I could use different colors or shapes for the
GCP; the image itself will then be rather a photograph of a fish on a white
background than a blue square; I just want to test with a simpler setup
before.

However, as I want to automatize the step of rectifying/georeferencing I am
looking for a way to autodetect these six points in the image. I am
thinking of tools like pattern/face recognition that are able to autodetect
objects (e.g. eyes, points etc.) and extract their position (coordinates)
within that image. I assume these coordinates together with their "true"
position could then be used for rectifying the picture using e.g. i.rectify.

Has anyone done this or a similar exercise before and can recommend tools
and approaches to auto-detect GCP from an image?

Any hints are welcome!

Best regards,
Johannes
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