ANALYSIS OF THE POSSIBILITY OF USING ARCHIVAL MAPS AS A SOURCE OF ELEVATION DATA

Abstract

One of the most popular sources of elevation data covering the most of the Earth's surface with spatial resolution of up to 30 m (1 angular second to be exact) is the SRTM model. This terrain model has two main disadvantages: it covers the area of the Earth between the parallels 54°S and 60°N only, and in some mountainous and desert areas there are gaps (voids) in the data. Additionally, it may not be suitable for more detailed visualization and analysis due to their limited accuracy. Therefore, the paper attempts to find an alternative source of elevation data. One of them may be archival maps, on which the terrain is presented by means of contours. By vectorization of such lines and adding respective attributes they can serve as a base for building digital terrain models. Examples of such maps are maps created in the period before World War II by Polish Military Geographical Institute (WIG). Although newer topographic maps or even more accurate spatial databases exist, it is assumed that as official materials WIG maps were not covered by copyright, so they are in public domain, just like SRTM. Conducted research and literature studies have shown that the issue of using contours extracted from archival topographic maps is not unambiguous. The lack of reproducibility in the results obtained does not allow making clear recommendations on the feasibility of using archival maps. Using a contour drawing as the sole source of elevation data, without any control, should be considered risky. On the other hand, it seems possible to use them as supplementary and perhaps refining material, but only in places where consistency with other data can be observed.