Imre Josef Demhardt:
Friedrich Wilhelm von Egloffstein's relief shaded pioneer maps of the Colorado River
Cartographica Helvetica 47 (2013) 13–26
It was only between 1845 and 1848 that the United States of America acquired the western half of its contiguous territory. Because there was no cartographic material available for this vast area, a number of reconnaissance expeditions were sent out in the 1850s. Based on topographic surveys he carried out during the Ives Expedition to the Grand Canyon, Friedrich Wilhelm von Egloffstein developed a heliographic technique in order to print a relief shading for his pioneer maps of the ravines of the Colorado River.