geodatabase

aamirzaman — Tue, 09 Oct 2012 19:12:39 GMT

what is the difference between clockwise and couterclockwise polygons constructed from points??????????????/

Re: geodatabase

VinceAngelo — Tue, 09 Oct 2012 20:46:04 GMT

In what context?

Most formats require one of two possible topology rules: "Right hand rule" or "left hand rule".
Right hand rule, used by shapefiles, dictates that the geometry is on your right hand side as
you walk the perimeter. "Clockwise" and "counterclockwise" are not used, because they do
not always correlate to "handedness" -- The interior rings (holes) of shapefiles are counter-
clockwise. Left hand rule is used by most storage formats (including file geodatabase, ArcSDE
SDEBINARY and ST_GEOMETRY, Oracle's SDO_GEOMETRY, and KML (though Google describes
it as "right hand rule", where the top is in the direction of the thumb and the exteriors wrap
in the direction of the fingers *sigh*). The Open GIS Consortium decided to not specify
handedness in the GML specification, but does require that interior rings must be in the
reverse orientation of exterior rings (and, IIRC, that all exterior rings be in the same direction).
Most Esri applications will correct orientation during the construction process.

- V

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geodatabase

Re: geodatabase