Extraction and recognition of map symbol from Topographical Map
Takashi Hoshi
Institute of Information Science and Electronics
University of Tsukuba
Tennodai, Tsukubam Ibaraki, Japan
Toru Takaki
Master's Programs in Scientific Technology
University of Tsukuba
Tennodai, Tsukuba, Ibaraki, Japan
Abstract
Recently, combination of topographical map data and remote sensing image data is socially required. In this paper, extraction and recognition of map symbols from completed topographical map is described, in order to get more useful information by combination of topographical image with remote sensing image. But there are great many symbol images in topographical map. Some symbols overlap one another, so it is difficult to extract and recognition of map symbols. The method with hole feature for recognition of map symbols will be shown. Some symbols in a topographical map on a scale 1:25,000 are used as the research data.
1. Introduction
At present, maps are used in many fields. In highly information society, digitization of map information which called "computer mapping" has been required for more efficient utilization. Maps are almost printed matter, but maps have a vast amount of information. With computer mapping, it will be possible to use geographical information with other media. Some institution management systems such as electric light pole and wire, and water pipe, are based on the geographical information. Combination of topographical map data and remote sensing image data make it easy to analyze data, and it is socially required. To use geographical information, map information such as symbols, characters and some lines must be taken, and a database which includes map information's must be established. There are two methods to establish map database. The first is digital mapping with map data which extracted when map is drown up. The second is extraction and recognition of map information data from ready-made map is the second.
The purpose of this research is to extract and recognize map symbols from ready-made topographical map to get geographical map data. But there are great many symbol image in topographical map. Some symbols overlap one another, so it is difficult to extract and recognize map symbols. For overlapped image, using hole feature would be very useful.
In this paper, recognition of map symbols with hole feature is described. A topographical map on a scale of 1:25,000 is used as the research data. Figure 1 is an example of such map symbols.
Figure 1 Map symbolsin topographical map
