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COMBINING PHOTOGRAMMETRY AND LASER SCANNING FOR DEM GENERATION
IN STEEP HIGH-MOUNTAIN AREAS
M. Ziiblin 3 ' *, L. Fischer b and H. Eisenbeiss 3
“Institute of Geodesy and Photogrammetry, ETH Zurich, 8093 Zurich, Switzerland, +41 44 633 32 87 -
zueblinm@ethz.ch, ehenri@geod.baug.ethz.ch
b Glaciology, Geomorphodynamics and Geochronology, Department of Geography, University of Zurich, 8057 Zurich,
Switzerland, + 41 44 63 551 19 - luzia.fischer@geo.uzh.ch
Youth Forum
KEY WORDS: DEM/DTM, LiDAR, Image Matching, Glaciology, Landslides, Snow Ice, Change Detection, Orientation,
Multitemporal
ABSTRACT:
This study presents the processing of both aerial and oblique images as well as LiDAR data of the Monte Rosa east face, an
extremely challenging environment in the European Alps due to the height, steepness and ice coverage of the rock wall. New
techniques of airborne LiDAR data acquisition are combined with established photogrammetric processing methods of aerial images
to develop high-resolution DEMs for different epochs since 1956. Furthermore, a novel approach for DEM generation from
helicopter-based oblique photos is introduced. Different software solutions for image processing and DEM generation are used and
evaluated for applications in such steep high-mountain terrain. Reliability and accuracy as well as usability of the different data sets
is shown and finally DEM subtractions give an insight in the strong topographic changes in the Monte Rosa east face within the
investigated timeframes.
1. INTRODUCTION
The Monte Rosa east face, Italian Alps, is one of the highest
flanks in the Alps (2200-4600m a.s.l.). Steep hanging glaciers
and permafrost cover large parts of the wall. Since the end of
the Little Ice Age (about 1850 AD), the hanging glaciers and
fim fields have retreated continuously. During recent decades,
the ice cover of the Monte Rosa east face experienced an
accelerated and drastic loss in extent. Some glaciers have
completely disappeared. New slope instabilities, detachment
zones of gravitational mass movements developed, enhanced
rock fall and ice avalanche activity were observed (Kaab et al.,
2004; Fischer et al., 2006).
Figure 1 : Monte Rosa east face, seen from Monte Moro
Mass movement processes have taken place all times because of
the height and steepness of the Monte Rosa east face. Over the
recent two decades, however, the mass movement activity in the
Monte Rosa east face has drastically increased and several large
rock and ice avalanche events occurred. In August 2005, an ice
avalanche with a volume of more than lxlO 6 m 3 occurred and in
April 2007, a rock avalanche of about 0.3x10 6 m 3 detached
from the upper part of the flank (Fischer et al., 2006).
For the investigation of the Monte Rosa east face, remote
sensing based techniques are crucial due to the inaccessibility
of wide areas of the rock wall. Steep and high rock walls are an
extremely challenging environment for effective data collection.
This study is done within a pilot project for multidisciplinary
investigations of such large and steep high-mountain flanks
integrating different investigation techniques and data sets to
achieve exacting spatial and temporal resolution. DEMs
represent the core of most investigations of high-alpine flanks
and they are crucial for geomorphic and morphometric analyses.
A highly promising, yet in high-mountain areas rarely exploited
method is the coupling of laser scanning data with
photogrammetric analyses of terrestrial and aerial images, to
extract topographic features and changes from DEMs.
Main objective of this paper is the investigation of DEMs
developed with different methods for different times, with
regard to accuracy and their usability for investigations of the
drastic changes in glaciers and bedrock in the Monte Rosa east
face.
2. DATASETS
Available data sets for the Monte Rosa east face are terrestrial
images, aerial images and high-resolution laser scanning data
(Tab. 1). Aerial images in image scales of about 1:12’000 to
