A spherical polygon is "a closed geometric figure on the surface of a sphere which is formed by the arcs of great circles." (from Spherical Polygon). What I would do -- since there are an infinite number of rectangles of any given side centered on a given point -- is find the intersections of the great circles 1km north, south, east, and west of your point.

For question 2, try Spheres: Miscellaneous Algorithms. They do mention that it can be rather difficult. If your rectangle is oriented so its sides are exactly east-west and north-south, it's much easier.

emc

Insisting on perfect safety is for people who don't have the balls to live in the real world.

—Mary Shafer, NASA Dryden Flight Research Center

In reply to Re: Manipulating Longitude and Latitude Information by swampyankee
in thread Manipulating Longitude and Latitude Information by Anonymous Monk

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