# Georeferencing files that are orthogonal to a point on a sphere

I have about 65000 photos, each of them a square where an inscribed circle is radius 1 degree.

Each of these photos has an associated latitude and longitude of the center.

I'm trying to figure out how to georeference these photos with gdal so that I can warp them into a large, more sane latlong coordinate system. Once I figure out one of them, it will be trivial to automate the rest, but I just can't figure out how to properly georeference an orthogonal photo.

For instance, tile 1 has a central latitude and longitude of 0. Further, along the central X-axis it occupies 1 deg and along the y-axis, it occupies 1 degree. Using the attached photo as a guide:

NOTE: (long, lat) A: 0,0 B: 0,.5 C: .5,.5 D: 0,-.5 E:-.5,-.5

The next photo in this series along longitude would have the following coordinates:

A:1,0 B: 1,.5 C: 1.5,.5 D: 1,-.5 E:.5,-.5

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Likewise, a photo at the pole would have a central latitude of 90 and longitude of 0. So

A: 0,90 B: 0,89.5 C: 90,89.5 D: 180,89.5 E: -90,89.5

Further, the next photo in this series would be rotated by 1 degree. So

A: 1,90 B: 1,89.5 C: 91,89.5 D: -179,89.5 E: -89,89.5

An so and, so forth.

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My proposed solution is something like:

gdal_translate -a_srs "+proj=ortho +lat_0=0 +lon_0=0 +a=6378140 +b=6378140 +units=d" input_000_00.jpg output_000_00.tif


But, when I do that and attempt to warp it, I get the following:

ERROR 1: Unable to compute a transformation between pixel/line and georeferenced coordinates for test17990.tif. There is no affine transformation and no GCPs.

You have specified degrees as units, but not added any information what coordinates your corner points have. Apart from that, +units=d is not listed with proj -lu and might be ignored.
You may try gdal_translate with -a_ullr, or add GCP points with -gcp.