in order to minimize the vertical error caused by a horizontal and vertical offset between the reference digital elevation model and the test dataset, the photogrammetrically derived dems were co-registered according to nuth and kaab(2011) using a als as the master. this method is especially designed for the co-registration of dems in highly dynamic areas such as glacial landsapes and has been used for similar approaches in high alpine environments(joerg). it uses the unique differences in a raster cell elevation divided by the tangent of the local slope and plotted