Estimation of an Unknown Projection from a Map and its Applications

This paper presents new methods for the detection of an unknown map projection and its parameters from a map. Corresponding 0D2D elements both on the analyzed map and a sphere (or a reference map) represent the source matter for the analysis. The following cartographic parameters (i.e., constants of a projection P) are estimated: R, k, k, 0, 0, Δx, Δy. Our solution minimizes L2 norm of residuals and allows for the exclusion of incorrectly drawn elements from analysis. Both on-line and offline methods of the detection are supported. Results are presented for early maps from the Map Collection of the Charles University and David Rumsay Map Collection. All algorithms were implemented in new detectproj SW, which supports more than 50 map projections and several operating systems.