Edge detection in segmented non-convex space polygon

Survey data in use in Civil Engineering consists of points described with XYZ coordinates. Closed shapes, like lakes described with a number of such points are immediately recognizable to humans although points are grouped in unconnected and unrelated lines. Automatic processing of those closed shapes is required if computer analysis is to be performed, i.e. we would like to produce a finite element mesh of the lake. In order to perform meshing one has to be able to determine whether a point is inside or outside of the space polygon, i.e. polygon edges have to be detected. Special computer procedures have been developed for edge detection. The most challenging part is detection of overlaps of edge lines which has been solved with specially modified Fourier transform procedure. Above procedures are applied on a real-life example for creating a finite element mesh of lake “Botonega” in Istria.