Polygon in TargetAreaType

["McGarry, Donald P." <dmcgarry@mitre.org>]

Carl and others-

Question:

The Polygon element in targetArea is a list of lat lon pairs that represents a polygon.  However, one problem that I have noted when storing polygons in a geospatial database, or exposing to GIS tools is RingOrientation.  Notably, you normally follow the “left-hand” rule, which states that if you are walking the polygon you left hand should be pointing towards the center of the polygon area, which results in a counter-clockwise representation of points in the polygon.  If this is the case, I think our example in the DE documentation was constructed using the opposite linear ring orientation.  When validating a polygon, do we assume a certain ring orientation, or state that it can be either or, and just take the case that doesn’t span multiple hemispheres?

 

Don McGarry

The MITRE Corp.

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Cell: 315-383-1197

dmcgarry@mitre.org