Algorithms

Detecting Mouse Hover over Irregular Shapes

The classic, brilliant PNPOLY algorithm that dates back to 1970

Snapshot of simply.earth, demonstrating the use of mouse hover to identify countries

W. Randolph Franklin’s “point inclusion in polygon” algorithm weighs in at just seven lines of C code. It’s intuitively easy to understand, yet fast enough to work with sophisticated GIS datasets. It’s one of those gems that every advanced…