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identify & compare to a polygonal area? [message #54658]

Fri, 29 June 2007 10:09

Josh
Messages: 21
Registered: June 2007

Junior Member

Morning all,

I'm plotting a map of elevation data (by lat/lon coords) over a lake
and the surrounding land. I would like to identify only those points
which are over the lake and make use of them. I do not need a level
of detail that defines the precise shoreline; I was thinking I could
identify a polygonal area within the lake (it would be concave...
problem?) and then have a comparison: if the lat and lon are contained
within the polygon, do something with that data point.

The other important detail is the spacing of these points... there are
on the order of 30,000 x 3,000 points in the rectangular map grid
containing this lake. The lake probably fills only 1/8 of the grid,
but it's diagonal orientation causes it to extend to all sides of that
30,000 x 3,000 point window.

As always, all thoughts are appreciated!
-Josh

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