Modeling and implementation of situation symbols in emergency thematic cartography

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.