geojson/draft-geojson — pull request #43 by pramsey (2014-08-06 20:49:29+00:00)
Title: Ring orientation to clarify meaning of large/dateline crossing polygons

It's possible (nay likely) that geojson will end up being created in both planar and spherical visualization systems. An open question for any ring on a sphere is: what part of the sphere does it bound? For planar and spherical systems, seemingly obvious answers get confused. It might be common on a planar display to draw a bounding box that covers "most of the world": POLYGON((-170 -80, 170 -80, 170 80, -170 80, -170 -80)). A spherical system interpreting the same polygon would probably draw a narrow box around the dateline. However, if you know the orientation of the ring, then the bounding question becomes obvious. This is also important for rings that cross the dateline: do they cover a small area of the Pacific, or a long narrow band all the way across the world, orientation can clarify that.