[PROJ] Geodesic buffers/offsets?

[Lesparre, Jochem]

Would this be a solution for a ellipsoidal buffer at geodesic distance around a very large polygon?:
1. Create points at a regular small distance along the polygon contour;
2. For each point: use PROJ's geod function to compute a large number of points on a "circle" at the preferred buffer distance, by taking regular small azimuth increments;
3. Connect the outer points with a concave hull.

Step 1 and 2 are straightforward but computational expensive, as the number of points you need grows with the product of the perimeter of the polygon and the buffer distance. Step 3 is a bit tricky, but if you compute points close enough, this is possible e.g. with a morphological closing (using conventional buffers).

Jochem


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