Chris Hill-Scott 99a8a4fd48 Don’t combine polygons with different projections ...

When we combine simplified polygons from different areas we try to use
the polygons that are defined in metres as a speed optimisation.

This doesn’t work when those polygons are in several different
projections because the distance in metres is relative to the edge of
the projection. Just naively choosing one projection means that some
of the polygons will shift position on the earth by 100s of kilometers
once they are converted back to degrees.

To avoid this we need to:
- check for situations where we have polygons in multiple different
  projections
- transforms these polygons back into degrees and let `Polygons` pick a
  common projection for all of them before doing any
  merging/smoothing/etc.

2021-12-07 14:16:54 +00:00

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