Open Session - SWISS GEOSCIENCE MEETINGs

12.1
A 3D geological model of North-East Switzerland, a GIS solution
Jordan Peter*, Schwab Marco*, Schneider Heinz*, Schnellmann Michael**, Weber Hanspeter**, Neaf Henry*** & Alber
Wilfried****
* Böhringer AG, Mühlegasse 10, 4104 Oberwil
** Nagra, Hardstrasse 73, 5430 Wettingen
*** Büro für angewandte Geologie, Vadianstrasse 41a, 9000 St. Gallen
**** Albert Consulting, Altenburgstr. 30, 5430 Wettingen
This paper presents a geological 3D model of northern Switzerland (from Oensingen to Lake Bodan). It consists in a 25m
raster grid corresponding to the DEM25 of the Federal Office of Topography. It is based on an extensive collection of data
about the underground: geological maps, historical isolines maps, borehole data, seismic data and geological profiles were
used to construct the elevation of 4 important geological horizons. The raw data are the basis for the construction of isolines
that were designed from experts in a GIS environment and only them where used as input for interpolation. In order to
model the discontinuities and faults, the construction of isolines and the interpolation were performed in separated segments
and merged in a further step.
This extensive work of transposition of geological data into Isolines originates in the facts that all classical interpolation
methods (IDW, Spline, Kriging) applied on points do not correctly represent the geological pattern expected between hard
data (e.g. boreholes). Geological interpretation and accepted geological concepts have also better been integrated into the
model.
The resulted model represents finally the stage of knowledge about the extent of a geological horizon and incorporates an
“interpolated” summary of numerous source of information about the underground. This opens the door for landuse management
in the vertical dimension, underneath the biosphere.
12.1
Analysing landslide features through scale using the wavelet transform –
Theory and application to the earth flow type landslide of Travers
(Switzerland)
Kalbermatten Michael*, Turberg Pascal**
* Laboratoire de systèmes d’information géographique, Ecole Polytechnique Fédérale de Lausanne, Ecublens, CH-1015 Lausanne (michael.
kalbermatten@epfl.ch)
** Laboratoire de géologie de l’ingénieur et de l’environnement, Ecole Polytechnique Fédérale de Lausanne, Ecublens, CH-1015 Lausanne
The analysis of specific features of a landslide is often conducted through visual terrain assessment. In recent years, LIDAR
(LIght Detection And Ranging) data acquisition has made it possible to produce high resolution (0.5-2 meters resolution) digital
elevation models (DEM). The visual analysis of high resolution DEMs is a new way used by geologists to characterise
landslide features through the abstraction of scale-dependent features. Thus, the geologist carries out a multiscale analysis
of the high resolution DEM due to the fact that geological features (composing a landslide e.g.) are not visible at one specific
scale, but nested in each other.
The wavelet transform (Mallat, 2000), is a localized frequency analysis (or filter) for image generalization. It is possible to
divide the continuous scale into discrete scale intervals. At each discrete scale level (or generalization level), we can analyse
high frequency structural features and reconstruct these features at high resolution.
We present a case study where we assess the scale dependence on a landslide located near Travers (Val-de-Travers, Canton of
Neuchâtel, Switzerland). A LIDAR survey had been carried out one month after the landslide. Derived from these raw elevation
data points, collected through LIDAR, a DEM was interpolated (1 meter resolution).
The study area was visually and geologically analysed by a geologist. Thereafter the results were compared to the images
obtained by the wavelet transform details coefficients.
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Symposium 12: Data acquisition, Geo-processing, GIS, digital mapping and 3D visualisation