Hi,
I was hoping to use GDAL for testing when two convex polygons intersect. I was
able to do this with something similar to:
polyOne->Intersects(polyTwo);
Both polyOne and polyTwo are OGRPolygon and are defined in geographic
coordinates, i.e. latitude and longitude (decimal degrees). I've also set the
spatial reference of the polygons to 'SetWellKnownGeogCS("WGS84")'. Also, I've
built GDAL with GEOS.
My question is this, what coordinate system is the intersection calculated in?
Looking through the code, it appears that GDAL uses GEOS for the intersection
test, and GEOS seems to rely on JTS for the intersection test. However, JTS
describes itself as providing '... algorithms for processing linear geometry on
the 2-dimensional cartesion plane'.
So, as an example, if my polygons each contain three vertices, are they treated
as spherical triangles in a geographic coordinate system (with curved edges)
when the intersection test is performed? Or, are then treated as flat triangles
with straight edges in some Cartesian / 2D coordinate system.
I appreciate any help answering this question,
Silas
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