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Rus I.,Babes - Bolyai University | Balint C.,Geo Map SRL Oradea Romania | Craciunescu V.,Remote Sensing and GIS Laboratory | Constantinescu S.,University of Bucharest | And 2 more authors.
Acta Geodaetica et Geophysica Hungarica

Old cartographic documents represent a valuable resource in reconstructing the natural and built environment evolution. In order to integrate such maps with recent geospatial datasets, in GIS environment, some preparatory actions need to be done. This includes scanning, color enhancement, georeferencing and reprojection. From our experience, when it comes to collections with a large number of map sheets, georeferencing is the most meticulous and time consuming process. Traditionally, this is done manually, by carefully selecting points with known coordinates. To overcome this disadvantage and to increase the rectification precision an automated procedure was created. The whole process of map sheet georeferencing is done by a specially developed tool, called "findlines", which relays on radon transform to extract, even in degraded and noisy conditions, all the straight lines from the map graticule network. Then, by knowing the distance between the graticule lines and the relation between the map name and lower-left corner coordinates, it is possible to automatically associate real coordinates to each intersection points in the graticule. Finally, the points are used along with GDAL to rapidly georeference each map sheet. The method was first successfully tested with modern topographic maps. To evaluate the procedure with old cartographic documents we select the 1:20 000 Romanian maps collection, under Lambert-Cholesky (1916-1959) projection system, as test data. The basic map, called "Plan Director de Tragere" was drafted under 1:20 000 scale in 2 118 drawings, covering all the Romanian territory. Each map sheet is 75 cm wide and 50 cm high and has a direct relation between the name and the lower-left corner coordinates. The maps were also successfully georeferenced using the findlines utility. Depending on the selected resample method, the time needed to georeference each map sheet, using 150 control points, ranged between 3 and 15 minutes on a normal computer. That proved the method efficiency and flexibility. Any map series with a regulated graticule grid and a logical relation between the name and the spatial position can be georeferenced using this approach, without any human intervention. Source

Craciunescu V.,Remote Sensing and GIS Laboratory | Flueraru C.,Remote Sensing and GIS Laboratory | Stancalie G.,Remote Sensing and GIS Laboratory
Acta Geodaetica et Geophysica Hungarica

The advantages brought by high resolution satellite data in activities related to flood mapping and flood monitoring are well know in the scientific community. The paper aims to prove that slighter older geospatial documents, such as historical maps, are also a valuable resource for cartographers and decision makers to achieve a better understanding of flood patterns and evolution. Some preparatory actions are needed in order to integrate the old maps into GIS environments for advanced analysis. This includes scanning, color enhancements, georeferencing, reprojection and metadata creation. To illustrate the process, the paper includes a real case scenario: the April 2006 Danube River flood. For one of the most affected sectors along the Danube, close to Rast village, three generations of historical maps (the Austrian 1:200 000 'degree maps', the Romanian 1:20 000 'Lambert-Cholesky' maps and the Soviet Union 1:100 000 'Gauss-Krüger' maps) were processed and included in a large repository. At any time, the maps can be identified and accessed through open standard protocols like CSW and WMS. In this way, we were able to integrate and analyze the flood water masks, extracted from satellite data, along with the historical data sets. The results were very promising. It was possible to understand some flood patterns and to clearly demonstrate that, after the dike failure, the water filled up an area which in the past, before river regulation, was the natural Danube floodplain. Source

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