Symbol recognition and surface reconstruction from topographic map by parallel method

The authors reconstruct three dimensional surfaces described by contours on topographic maps. When the elevations of the contours are available, this is an easy problem to solve. However, the authors do not have these elevations and can use only sparsely distributed elevation values noted on the map. This is a difficult problem even for humans to solve. They have developed a method for reconstructing three dimensional surfaces using only contours without matching elevations and these sparsely noted elevation values on the map as input. Numerals and symbols are recognized by the multitangled parallelism (MAP) matching method, while small dots and lines are extracted by the MAP operation method. These results are then used to used to determine the value, position, and attributes of the elevations marked on the topographic maps. The authors define an energy function for reconstruction of the surface. The function integrates three kinds of constraints: smoothness, fitness, and contour. The energy function can be minimized by solving a large linear system of simultaneous equations. The experimental result is a surface reconstructed from a 25,000:1 scale topographic map of the Tsukuba area