In the Republic of Croatia there is a long tradition going on in carrying out systematic levelling works. These works have resulted, in the period of about 120 years, with the establishment of three fundamental levelling networks of geometric levelling. These are precise levelling network of the Austro-Hungarian Monarchy, I. levelling network of high accuracy and II. levelling network of high accuracy of former Yugoslavia. These networks are the basis of height system of the Republic of Croatia, and accompanied by adequate definitions of height datums they are used even today for solving fundamental and applied geodetic tasks and scientific researches.
Various spatial data sets of high quality and homogeneity allow a higher level of multidisciplinary research. The study is aimed at providing a clearer understanding of the technical and semantic aspects of the quality of historical maps, especially with respect to positional errors, through the georeferencing process. Georeferencing the system of historical map sheets with high precision over a large area is not easily incorporated into the less complicated standardised process. Significant problems may occur in rough mountainous regions, especially as many of the areas were not accessed at that time and therefore not surveyed. The standard process of georeferencing comprises mosaicking of singular map sheets to a seamless map, referencing with identical points, and applying an appropriate transformation method. The quality of georeferenced maps is assessed with statistical and visual parameters. The enhanced process additionally integrates descriptive (textual) information about the mapping processes, derivative georeferenced data sets as land use analysis, and Monte Carlo simulations. This approach allows a more detailed understanding of the quality and consequently improves a georeferencing process for any historical data sets. The First Military Survey maps of the Habsburg Monarchy (Josephine survey), produced between 1763 and 1787, were used as study data and the rugged Julian Alps of the Triglav National Park in Slovenia were employed as the study area.