Abstract
Analysis of the map projection, involving the estimation of the constant values of the projection and the map parameters, minimizing L_{2}norm of residuals on identical points, belongs to modern methods of cartometric analysis. Such an analysis is beneficial for early, historical, or current maps without information about the map projection. The importance of the map projection analysis refers primarily to the refinement of spatial georeference for medium- and small-scale maps or to the appropriate cataloging of maps. In georeferencing small-scale maps, it is incorrect to directly transform the analyzed map into a projected coordinate system and neglect the influence of the different map projections.
Since the publication of the method in 2006, a considerable amount of improvements have been made, especially in the stability of the detection process and the convergence rate. In addition, an open-source software tool detectproj has been developed as a practical application. Currently, more than a hundred map projections are supported, and ten parameters of the map projection (constant values of the mp projection) and analyzed map (map scale, rotation, shifts) are estimated. Furthermore, another improvement, the possibility of georeferencing the analyzed map using the method of inverse reprojection, was added.