Robustness in GIS algorithm implementation with application to line simplification

The sensitivity of computed results to implementations of algorithms in GIS is considered in this paper on the example of a precisely defined recursiv e variant of the Ramer-Douglas-Peucker line simplification algorithm (calle d the R-D-P algorithm). We establish a robust version of the R-D-P algorith m where the determination of the simplification is rounding error free if t he data are already machine numbers. Under these assumptions, the results a re reproducible which is not the case with other versions of the algorithm.