[task #13658] Work on concave polygons too

[Sachin Kumar Singh]

Follow-up Comment #26, task #13658 (project gnuastro):

I read the paper about the internal algorithm used in astronomy.net. I
understood the algorithm and the required thresholds. I realised how this was
related to the non-linear warping task. This is a rough summary:

The astronomy.net using a geometrical hashing algorithm by using predefined
indexes from an existing survey and uses a quad asterism. Thereafter they
divide the catalogue to be searched on in various healpixel and find the
required index after a few passes and if the result passes a bayesian
threshold. It used a 4 kd-tree to store and retrieve hashes. Now finally the
wcs info of the index is used in the calculation of the positions and any
transformations. Also wcs information in the fits files can store any
distortions information in them(the key-value pairs)

But now if such a system already exists(and already written in c), what should
I do about it for the summer project. Also, the info in all those papers is a
little overwhelming at first. Hence please tell me a brief overview of how
should I proceed to make them all fit together to make up my project which can
be completed within this span of time and is not too complex to implement?




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