Optimal usage of territories appears as applicable problem at the present time. Its description is hold in geographic information systems (GIS) and may be used for solving ecological, administrative, transport and logistical tasks. We consider to use topographic maps for production GIS. By now algorithms for reconstruction of plan of contour lines are developed. This plan of contour lines appears as matrix of spatial scattered data, which are needed to interpolate for production a digital terrain model. There are some common algorithms for interpolation (linear, cubic spline, natural), but they aren’t fit for good shape reproduction. We consider an algorithm based on 3-class classifier of points. Points of 1st class are between two contour lines and are interpolated by n nearest points of the nearest contour line and the nearest point of another line. Points of 2nd class are inside of one contour line, accord with peaks or depths and are interpolated with similar algorithm and value of extremum which is taken by mark of height is used. Points of 3rd class are between a contour line and boundaries of topographic map; their interpolation may be taken by union of several maps and they become points of 1st class. Processing speed, maximal error and mean-root square error are used as measure of quality. Considered algorithm has shown improvement by comparison with other methods with decrease of errors and nonthreatening increasing of processing time.

Keywords: interpolation, geographic information system, topographic map, digital terrain model, scattered data