I want to find the shortest distance between two SqlGeography polygon. I know there is a method
You should define a
GEOGRAPHY in Counter Clockwise order. If you define it CW, it will be all the world except the region you are defining:
DECLARE @G1 GEOGRAPHY = 'POLYGON ((1 1, 3 1, 3 3, 1 3, 1 1))'; DECLARE @G2 GEOGRAPHY = 'POLYGON ((45 45, 45 46, 44 46, 44 45, 45 45))'; //This is what you have defined DECLARE @G3 GEOGRAPHY = 'POLYGON ((45 45, 44 45, 44 46, 45 46, 45 45))';
@G1: point order is CCW so @G1 is a polygon containing
@G2: point order is CCW so @G2 is a polygon containing
@G3: point order is CW so @G3 is a polygon containing the entire world except the @G2 polygon. It also contains the @G1 polygon, so the shortest distance between @G1 and @G3 doesn't have any meaning.
ReorientObject() method, you can toggle between CW and CCW geographies. So if you try:
The result would be
GEOMETRYCOLLECTION EMPTY because they contain the same region. So they intersect and the result of
ShortestLineTo returns a
LINESTRING EMPTY because they intersect each other.
You can check if a polygon contains too large of a region by checking the
EnvelopeAngle so you are made aware of mistakenly defined geographies.
As shown in the picture,
EnvelopeAngle=180 means that polygon contains a very large region of the world.