The rate at which climate change is causing the Alpine glaciers to melt can be determined from the 120-year-old mountain maps created by Sebastian Finsterwalder. For decades, this multi-talented scientist tirelessly trekked through the mountains, analyzed photos and took to the skies in a hot-air balloon to survey the land. In the process, he developed geometric methods which are still used today by the algorithms of modern 3D software.
Armed with crampons, a pickax and measuring instruments, the young mathematician and geodesist Sebastian Finsterwalder climbed the Ötztal Alps in 1889 along with two research colleagues and a porter. The undertaking was both challenging and dangerous. They spent weeks surveying moraine ridges, glacier edges, fault lines and cliff faces – all to create the first accurate map of the Vernagtferner glacier. Just three years later, in 1892, Finsterwalder was teaching at Technische Hochschule München, having acquired a professorship. He became the first person to map all of the Bavarian glaciers in the Wetterstein mountains and the Berchtesgaden Alps – both on foot and from a hot-air balloon.
Finsterwalder’s life’s work as a geometrician, geodesist, physicist and engineer remain invaluable to this day. His mountain maps, for instance, show how far Alpine glaciers have retreated over the past 120 years due to climate change. His mathematical approach created an all-important scientific foundation for the task of surveying the earth’s surface. He used all the intricacies of descriptive geometry to obtain an accurate picture of the landscape – using only photos, drawings and as few actual measurements as possible. The methods he discovered are still important today for satellite surveying and the 3D software used by engineering companies, and even for computer games, animated films and 3D cinema.
Today, every three-dimensional computer display uses algorithms based on Finsterwalder’s calculation methods. What he referred to as “position resection” hides the invisible lines behind an object (the hidden line algorithm) in CAD programs for instance. Methods described by the mathematician in his writings are still used today. The difference nowadays is that it is mostly software doing the calculations.
Finsterwalder introduced terrestrial photogrammetry, allowing him to determine the shape of a mountain without actually going near it, using only two photos taken from the valley or from a hot-air balloon. To do this, he used the stereoscopic effect. Similar to spatial vision, it involves observing the same object from two different positions located a short distance from each other. Using the relative orientation of objects, he then determined the three-dimensional coordinates of the object. To this day, photogrammetry is still nearly always used for three-dimensional modeling of satellite, radar or aerial images.
Compared to 1850, the glaciers of the Alps have shrunk to one third of their previous volume and one half of their former surface area. When Finsterwalder was conducting his surveys in 1889, he never could have imagined this scenario. Indeed, he and his research colleagues told fascinated tourists who were sharing their hut one night that the glacier was in fact two kilometers longer 40 years ago – but that it would surely start growing again soon. This was before global warming. At that time, the climate fluctuated on average every 35 years between cool/wet and warm/dry, as a meteorologist would be able to prove soon afterwards.
“He [Sebastian Finsterwalder] never held back his ideas and never considered monetizing them through patents. Instead, he always unreservedly and unselfishly shared his findings and discoveries with friends, students and the public.”
Geodesist Otto von Gruber, 1937, on the 75th birthday of Sebastian Finsterwalder