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The POLY_AREA function returns the area of a polygon given the coordinates of its vertices.

It is assumed that the polygon has n vertices with n sides and the edges connect the vertices in the order:

[(x1,y1), (x2,y2), ... , (xn,yn), (x1,y1)]

such that the last vertex is connected to the first vertex.

This routine is written in the IDL language. Its source code can be found in the file poly_area.pro in the lib subdirectory of the IDL distribution.


Result = POLY_AREA( X, Y [, /DOUBLE] [, /SIGNED] )

Return Value

If either of the input arguments is double-precision or if the DOUBLE keyword is set, the result is a double-precision value, otherwise, the result is single-precision.



An n-element vector of X coordinate locations for the vertices.


An n-element vector of Y coordinate locations for the vertices.



Set this keyword to use double-precision for computations and to return a double-precision result. Explicitly set DOUBLE=0 to use single-precision for computations and to return a single-precision result. By default, if either of the arguments to POLY_AREA is double-precision, computations are done in double-precision; if both arguments are single-precision, computations are done in single-precision.


If set, returns a signed area. Polygons with edges traversed in counterclockwise order have a positive area; polygons traversed in the clockwise order have a negative area.

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