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I need to locate the fiducial marks in a huge set of old aerial photos. The fiducial marks are located along the borders of the image and I know very roughly where they are in the image. I have thresholded the image and created a sample image containing the 4 fiducial markers:

As seen in the image the markers vary slightly in shape and my initial tests with a SURF detector and a BruteForceMatcher didn't go well.

I have thought of using ICP in 2D on contours but I don't know how to combine those and my reading suggests that ICP might no be the right way to go. I have gone away from template matching due to the resolution of the images and the computational time required to find match the template.

I am fairly inexperienced in this field but can't help thinking that these shapes are so distinct that it should be fairly easy somehow to locate them. Can you help me along the way?

I need to locate the fiducial marks in a huge set of old aerial photos. The fiducial marks are located along the borders of the image photo and I know very roughly where they are in the image. I have to look for them:

The search area is thresholded the to remove any actual image and created a sample image containing the content (noise). Each photo contains 4 fiducial markers:markers and the following shows all 4 of them joined together in a small image:

As seen in the image the markers vary slightly in shape and my initial tests with a SURF detector and a BruteForceMatcher didn't go well.well. This might-be/is-probably due to my lack of knowledge about which detectors/matchers to use and their corresponding parameters.

I have thought of using ICP in 2D on contours but I don't know how to combine those and my reading suggests that ICP might no be the right way to go. I have gone away from template matching due to the resolution of the images and the computational time required to find match the template.

I am fairly inexperienced in this field but can't help thinking that these shapes are so distinct that it should be fairly easy somehow to locate them. Can you help me along the way?