Contour maps showing potential distributions or sequences of times of excitation are used to portray electrical events on surfaces of the body or the heart. Computerized construction of such maps provides a means for many maps of high accuracy to be obtained. The solution strategy divides the system into components for: 1) processing of the potential or time values to be shown on the map, 2) organizing of map geometry, reflecting the electrodes and their placement, 3) selection of map ″style″ , i. e. such things as the number of contour lines, and 4) drawing the contour maps. Procedures are described which are used routinely for numerous clinical and experimental protocols with highly satisfactory results.