Positioning and Spatial Search of Maps with undeterminable Projections
ISBN 978-85-88783-11-9
Authors
1Irás, K.; 2Nguyen Thai, B.
1EÖTVÖS LORÁND UNIVERSITY Email: iras@map.elte.hu
2EÖTVÖS LORÁND UNIVERSITY Email: posseidon@gmail.com
Abstract
Users who have already accommodated to various options of web map services show the same expectations about digital historical maps. Map collections and libraries constantly make efforts to follow new technologies. A current issue that map librarians often meet is the question and possibilities of georeferencing map sheets and setting them up in GIS for making spatial queries possible. In the case of those old maps that don’t show projection grids or the map content is inconsistent with the indicated coordinates, the best results of georeferencing may be highly distorted. This way, spatial queries cannot be done with success in a large amount of cartographic material. We make basic spatial queries when we need to know e.g. which maps of our collection show a specific area or whether a town or a settlement is indicated in a specific map sheet. Our research was motivated by such simple questions of map users. We aimed to develop the method of geolocating maps that cannot be precisely georeferenced because of their content. Another target was to create an easy to use tool for tasks where geolocation is important but it is not needed to use complex mathematical calculations and transformations. Geolocator of Historical Maps is intended to widen digital registration of maps in map collections and to facilitate place name search on scanned maps. Users don’t need to identify ground points with coordinates and distort the map images to projections because the system integrates a special solution for geolocating the sheets with a variable image grid system. The spatial connection and spatial queries are based on spatial database. Geolocator stores image grids set by the user (e.g. a map librarian) and their links to the free on-line map data base within the data sheet of the maps and highlights the areas in question after spatial queries. Spatial connection also make town search possible by entering town names, so it is not needed to transcribe the toponyms of the map sheets. Each component of the system is open source and available for free on Internet. Geolocator is part of a research project and is not intended for commercial traffic. In our paper, we present the operation, the structure and the technical background of the system.
Keywords
spatial search; old maps; grids