Molnár Gábor – Timár Gábor – Biszak Előd: Can the First Military Survey maps of the Habsburg Empire (1763-1790) be georeferenced by an accuracy of 200 meters? Conference: 9th International Workshop on Digital Approaches to Cartographic Heritage, Budapest, 2014. Volume: 9. 127–132.

9th International Workshop on Digital Approaches to Cartographic Heritage

Budapest, 4-5 September 2014

data input (GCPs) can also be obtained from the users of the published database, making a new, interesting application area of the social-web database building.

Figure 2. Overlay of the First Military Survey mosaic on the modern OpenStreetMap layer of Vienna.

The boundary problem

As it was mentioned earlier, the error vectors of the correction grid are compiled by bilinear interpolation of the ones at the GCP locations. It is an important experience that they should be interpolated indeed: extrapolation could result unacceptable errors. It is the typical case occurring at the boundaries of the regional mosaics (Fig. 3).

To avoid the extrapolation errors, we have to define GCPs along the boundaries of the mapped area/mosaic. If we do so, even at the boundaries, we have accurate results, and the zone of extrapolation is shifted to beyond the area of our interest, which is represented by white, blank area in the map sheets. This is the only way to make fit the mosaics of two neighboring provinces seamlessly.