Hi Ben
I have tried this library and it works
like a bomb!
Thanks a lot.
Riaan
Riaan,
Have a look at JTS:
http://www.vividsolutions.com/JTS/jts_frame.htm
"The JTS Topology Suite is an API of 2D spatial predicates and
functions."
"JTS provides a complete, consistent, robust implementation of fundamental
2D spatial algorithms"
Implemented in Java (there is also a C# port) and licensed under the LGPL, so
easily usable.
JTS implements a PointLocator class, which includes a intersects method:
intersects
public boolean intersects(Coordinate p,
Geometry geom)
Convenience method to
test a point for intersection with a Geometry
Parameters:
p - the
coordinate to test
geom -
the Geometry to test
Returns:
true if
the point is in the interior or boundary of the Geometry
Cheers,
Ben
GMail wrote:
Mike Morris wrote :
Riaan Koegelenberg wrote:
Have anyone ever done something like this? I
need to
determine whether this polygon then contain a specific
point (coordinates also in lat/long).
This is really, /really/! hard to do if you need any sort of acccuracy. The
Earth is a spheroid, not flat, so any 2D-based solutions are wrong.
Best is to search for Great Circle navigation code, or ask Mr Ulrich Schultz in
the Hydrographer's office - I don't think too many other people in the country
know the math involved.
Anybody who's done a surveyor's degree would have done the math - whether they
still remember it is another matter, but they should have the books still.
There used to be someone on the CLUG mailing list who worked with GIS's - you
might try posting there and see if he answers.
The difficulty of the problem depends on the size of your polygons, if they are
small (say plot sized) then you just need to transform lat & long. to grid
co-ordinates and use standard plane geometry. If they are large (say country
sized) then the earth's curvature is significant and straight sides are no
longer a good approximation so you need to work in spherical geometry.
Fritz Meissner
--
Ben van der Merwe
[EMAIL PROTECTED]
