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 Gábor Molnár* , Gábor Tímár** , Előd Biszak3*** * MTA-ELTE Geological, Geophysical and Space Science Research Group, Hungarian Academy of Sciences at Eötvös University, Budapest, Hungary [molnar@sas.elte.hu ] ** Department of Geophysics and Space Science, Budapest, Hungary [timar@caesar.elte.hu ] *** ARCANUM Database Ltd., Budapest, Hungary [biszakelod@gmail.com ] Can the First Military Survey maps of the Habsburg Empire (1763-1790) be georeferenced by an accuracy of 200 meters? Keywords-, georeference; historic maps; Habsburg Empire; First Military Survey; 18th century Summary: The First Military Survey of the Habsburg Empire was made after the order of Empress Maria Theresia, issued after the seven-year war (end of 18th Century). The scale of the survey sheets is 1:28,800. According to the processed literature, the survey has neither triangulation basis, nor clearly defined projection. Earlier, during the geo-referencing projects of the Hungarian SME Arcanum, the sheets were rectified in virtual mosaics for each mapped province. Some tens of the ground control points (GCPs) were defined by their mosaic image coordinates and the UTM coordinates of the respective zone. Twelve coefficients of a quadratic formula were estimated using these coordinates for each province. Using the quadratic transformation, the RMS errors occurred as high as several hundred meters, in case of larger provinces, even 1-2 kilometers. A new method is introduced now, consisting of two consequent steps, using cca. 200-500 GCPs per province. (1) Parameters of the best-fitting Cassini projection are estimated from the GCP coordinates. (2) The non-systematic RMS error (up to one kilometer) is handled by a NTv2 format correction grid (GSB), compiled again on the basis of the GCP coordinates. The still remaining error is in the magnitude of 100-200 meters, however it can be further refined in important areas, using a more dense GCP network. Introduction The topographic surveys of the Habsburg Empire have been a main target of digitizing, georeferring and nowadays also the web-publishing activity concerning the whole cartographic heritage of the world (Tímár et al., 2011; Biszak et al., this volume). The Second Military Survey (1806-1869) was geo-referred by providing a mathematical model of its native projection and locate the map sheets in that, using their corner coordinates in this grid (Tímár et al., 2006), the very same method that is described in the present volume concerning the Cassini maps of France (Tímár et al. A, this volume). This method cannot be applied to the First Military Survey (1863-1887) of the Habsburg Empire. First, the Austrian literature agrees on that the survey has no geodetic and therefore projection background (Hofstätter, 1989; Kretschmer et al., 2004). We argue this point, however without knowing or estimating at least the projection parameters, it should be accepted as a starting point. In the Vienna military archives we haven't found so far any description of any geodetic survey connected to the first topographic survey. At the beginning of this study, we can only state that the surprising accuracy of the map sheet content cannot be a result of any work without geodesy.
