## 1 Introduction  
If we want to learn what our landscape looked like 200 or more years ago, we have the opportunity to work with the first topographic maps, which record individual topographic elements in sufficient detail. These topographic maps serve as a memory of the landscape and show the state of our environment in the period before the Industrial Revolution. Cartographers can process and make these maps available in the current reference coordinate systems to a number of experts whose work is based on working with spatial data. These can be historians, geographers, environmentalists, demographers, ecologists, and others. Unfortunately, the topographic maps of that time were created with no geodetic basis, thus, it is not possible to use the standard georeferencing procedures that we know from use in newer mappings. In general, it is possible to consider the use of the map sheet index and image transformation using a projective transformation and map sheet corner coordinates. This method can be applied if we know the parameters of the used cartographic projection, the reference projection surface and the planar coordinate system [1]. This method cannot be applied to the First Military Survey (1763-1787) of the Habsburg Empire. The Austrian literature agrees that the survey has no geodetic and, therefore, projection background [2, 3]. The second option is to use the coordinates of ground control points (GCPs) with different types of transformations. Since the maps transformed in this way do not fit to each other after georeferencing due to inaccuracies of GCPs, it is possible to apply a dual approach. It is either possible to create a continuous mosaic of map sheets before georeferencing and then transform the whole image at once (used, e.g., in [1, 4]), or use a type of transformation that preserves the continuity of map sheets even after georeferencing (e.g., in [5, 6]). Our considerations on the issue follow the latter option, because we believe that, in this way, it is possible to eliminate some problematic aspects of the transformation of the entire mosaic at once. The aim of this article is to present a method for georeferencing multi-sheet map works, including its evaluation and analysis. The area of Bohemia was chosen as the test area on the maps of the First Military Mapping. In the second half of the 18 th century (1763-1787), the so-called First Military Mapping was carried out on the territory of the former Habsburg monarchy. It arose on the basis of the needs of the Austrian army after the Seven Years' War (1756-1763) [2]. Unfortunately, these maps were created without geodetic networks, using the _a la vue_ method, and their accuracy is not sufficient from today's point of view [3]. Individual map sections, _brouillous_, have rectangular shapes and dimensions of 61.8 cm by 40.8 cm. From this, we can deduce the use of a cylindrical type of projection. In some provinces (Bohemia, Moravia, Silesia, Hungary), it was possible to use existing [PERSON] maps [7] as a basis, probably also made in a cylindrical projection [8]. [PERSON] and [PERSON] use [PERSON]'s projection as a probable projection of the map [9]. As each map sheet has been processed separately, the map drawing does not fit exactly on the adjacent edges. Despite this, for a number of historical or environmental studies, there is need to work with mosaics of larger territories, preferably directly-mapped provinces. The ideal situation for the georeferencing of old maps is the knowledge of the used cartographic projection, including all parameters. If this information is not known, it is possible to try to estimate the projection and its parameters. This issue is thoroughly discussed in [10; 11], nevertheless, it is successfully applied only to small-scale maps. The procedure is actually based on the display of meridians and parallels on individual maps. For large and medium scale maps, to which topographic maps belong, it is practically impossible to reveal the used cartographic projection.