Rock drawing for topographic maps

The maps of the Federal Office of Topography swisstopo - the Swiss national mapping agency - are renowned for their combination of shaded relief, contour lines, scree rendering and rock drawing, which creates the so-called Swiss style of topographic mapping. During the era of analogue map production, rock drawing was executed with scribing on coated glass plates. With the ongoing computerization of cartography, swisstopo switched to a digital production line a few years ago. However, high-quality Swissstyle rock drawing for topographic maps is still a very labor-intensive process. At swisstopo, revisions to rock representations are carried out using interactive mouse-based drawing tools, as automated procedures do not currently exist. The Federal Office of Topography swisstopo and the Institute of Cartography of ETH Zurich therefore carry out a joint study to evaluate the potential of digital techniques for automating rock drawing. The first step of this project is a detailed study of the current manually drawn rock depiction, including design principles and geometric dimensions. This paper discusses current mousebased drawing techniques applied by swisstopo for their official map series and then shortly describes the graphical design principles for Swiss-style rock drawing. Metrics for individual rock hachures are included.