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# Latitude, Longitude, polygons, and points.

Posted on 2008-06-20

Hello,

I am trying to figure out a way to determine whether a give point on a map (literally anywhere on earth) falls within the bounds of a polygon drawn from a list of ordinal lat/lon points. The polygon could have any number of sides, as long as none intersect.

I am guessing that starting by converting the lat/lon values (which also have a N, S, E, or W associated with them) into a totally numerical representation is how I should start. If that is correct, what is the best way to do it?

For the record, I already have my lat/lon values converted to a decimal number rather than minutes and seconds, etc.

Does anyone have a good algorithm to determine if the point is inside a polygon that is mapped on the surface of the earth? I am looking for a very precise way to do this, as the precision is important in this case.