Even today, many topographic maps are “only” available in raster formats. OCAD provides a simple procedure to continuously transform raster maps into vector maps. Print films – either newly scanned or already available in digital - are loaded as background maps and assigned their true colours. The map appears on the screen in the original colours.

In an additional step, the map sketch is loaded with the map objects to be updated. In this case it is a geo-referenced orthophoto.

In map draft mode, the transparency of the drawing layers and the map background can be set individually.

A “delete” colour is defined for each true colour. This makes it possible to delete obsolete map objects in a specific colour layer without covering objects of other colour layers. For example, with the delete colour “green”, a cleared section of forest can be covered without covering the contour curves or the trail and street network.

Afterwards, the new situation will be added in accordance with the orthophoto. When hiding the map background, only the updated vector map objects appear.

For printing the updated map, the vectors are rasterised and reproduced in the print films in accordance with their true colours.

80% of the 1791 1:25,000 maps and all 1181 1:50,000 maps of France at the Institut Géographique National IGN were updated with this procedure.

smart updating of topographic maps
Institut Géographique National
IGN Paris
2/4 avenue Pasteur
F-94165 Saint-Mandé Cedex
France
www.ign.fr