Interrupted projection proposal.

[jjimenezshaw]

Hi

I have been developing an interrupted projection. We could consider it a "metaprojection", because it just call the proper base projection adjusted to create properly the gores (apparently that is the term).

Before I continue with it and do the documentation and tests (that is a lot of work), I would like to know if it makes sense.

It so far supports the projections "sinu", "tmerc", "cass" and "poly". Adding more cylindrical base projections should be easy.

Let me show you some outputs done with QGIS.

+proj=interrupted +base=sinu +gores=4

+proj=interrupted +base=tmerc +gores=4

+proj=interrupted +base=cass +gores=4

+proj=interrupted +base=poly +gores=4

+proj=interrupted +base=tmerc +gores=20

You can also specify non uniform gores, and change the central meridian.
+proj=interrupted +base=sinu +gores=L2,3,2 lon_0=45

Daan Strebe suggested me these papers:
https://cartographicperspectives.org/index.php/journal/article/view/cp42-strebe
https://research.manchester.ac.uk/en/publications/evaluating-map-projections-for-globe-making

The main use case could be (I think) in visual software like QGIS, to directly display the gores as you need them. I do not know how many people need gores. I personally like it, maybe because it makes explicit the connection to a real globe (watch https://www.youtube.com/watch?v=4RWcWSN4HhI at 1:10)

If you find it useful I can continue with it. If not, I can just leave the branch as it is now, and anyone interested can take the file interrupted.cpp and compile it.

[rouault]

That looks like a cool addition, and with a modest code footprint.