Indian topographic map symbols understanding system

Recognizing symbol is the first step in using a topographic map. Despite the prerequisite for extraction of information from topographic map, automated understanding of symbols is a challenging task. The objective of this paper is to explain the development of a system for automatic understanding of symbols from the Indian topographic map. The system has been developed making use of shape analysis method in which complex valued chain coding has been used for representation of the exterior boundary of the shape of the symbol. Fourier discrete transform and Auto-correlation function have been used to define shape descriptors. Classification and recognition have been implemented through template matching method and Similarity measures. The system is trained with 150 samples of each of 20 types of symbols from National digital topographic database (NTDB) for OSM of Indian topographic maps. The developed system is tested for 200 samples of each type of symbol from NTDB. It is found that 84.68% of symbols are understood correctly by the developed system. However, there are some inherent limitations in understanding the symbols from an actual map.