Modeling and implementation of situation symbols in emergency thematic cartography

摘要

According to the needs of emergency thematic cartography and the China''s existing ‘Specification for the military symbols’, the types of situation symbols that may be used in emergency thematic cartography were summed up in this paper. A comprehensive modeling was raised for these situation symbols and it is flexible for emergency thematic cartography. There are four kinds of situation symbols: contour symbol, simple arrow symbols, single arrow symbols and combined arrow symbols in this paper. The position line of the symbols is a Bezier curve or a polyline. The oblique axis parabolic algorithm and the Hermite interpolation algorithm are selected for smoothing the position lines of the symbols. The Douglas-Peucker algorithm is picked out for scattering the position curve. At last, this paper developed a cartographic system based on the national fundamental geographic information, and realized the modeling and drawing of the situation symbols with the cartographic system.