Frankfurt am Main
 |
 A
branch of the Barranco de las Lenas, a large erosion gully cutting deep
into the Holocene valley filling and the Miocene gypsum and limestones
below near María de Huerva (Zaragoza), is seen here through a wide
angle lens in April 1998 from 230 m flying height (see also enlarged
version). In the upper part of the image, where the campsite of the
EPRODESERT research team is set, agricultural terraces, cultivated until
the 1930s, are already being destroyed by the growing gully. The large
field in the lower right part of the images has lain fallow since 1991
under the European Union's set-aside programme and is now strongly affected
by sheet wash and rill erosion. The white sheet on the edge of the field
is the blimp's launching site. Original image scale 1:8300. |
  The
image on the left, taken in August 1996 from 125 m flying height, shows
in more detail (ground resolution of the original
photo approx. 3 cm) the upper part of the barranco, its various branches
of which some have been "cut off" and fallen inactive, and the remaining
isolated areas and towers covered with steppe gras (Lygeum spartum)
and lichens. Along the sheep trails on the abandoned fields, vegetation
cover has been reduced and erosion processes increase. The line running
through the image is the blimp's plumb line indicating flying height to
the blimp team on the ground. Right, the uppermost head-cut of the gully
is seen from 25 m height in April 1997. A 2 m-grid of ropes has been set
up on the area (EPRODESERT's test side MDH2), aiding ground survey of vegetation
cover, life forms and erosion processes. During 3 1/2 years of photographic
monitoring, the gully area covered in this picture has increased by a total
of 3,2 m². The red markers (seen better in the
enlaged
version) are ground control points for image rectification and georeferencing.
The sequence of images shown here is only a small selection of approx. 2000 photographs taken in the five test areas during 1995 and 1998. They have been chosen to give an impression of the wide range of scales and resolutions which can be achieved with the blimp system owing to its high flexibility in flying heights and to the use of different focal lenghts with the cameras. |
| Once digitized and georeferenced with the aid of image processing software,
digital maps with a ground resolution of 2.5 cm were prepared in order
to build up a process-gemorphological information system for the individual
test areas. Visual photo interpretation and on-screen digitising led to
maps of actual geomorphodynamics (below left) while automated multispectral
image classification was employed for mapping of vegetation density. From
digital elevation models generated from stereoscopic images by photogrammetric
analysis, slope (below middle), curvature and potential flow paths of runoff
water could be computed. Maps of several dates were combine for change
analysis, as seen below in the example of vegetation change between April
1996 and April 1997 on the test area MDH1, situated on the young fallow
land mentioned at the
first image. After several years
of abandonement, this field suffers from increasing geomorphological process
activity hardly prevented by a scarce vegetation cover due to several years
of drought, coupled with severe soil sealing and crusting. Other phenomena
mapped or automatically classified from the blimp's high-resolution photographs
include vegetation life forms, percentage stone cover and nano-relief (row
and furrow-pattern resulting from tillage). All maps were combined in a
raster GIS for statistical analysis emphasising on the relationships between
state and development of vegetation succession and geomorphodynamics (see
MARZOLFF 1999).
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| For a general overview of the test areas, as a cartographic base for
large-scale soil maps as well as for locating and documenting the sites
of rainfalls simulation and wind erosion experiments, soil pits and other
research sites, photographs taken from higher flying heights were mosaicked
for airphoto-maps like the one shown below of EPRODESERT's northernmost
test area in the High Pyrenees. A GIS based on the airphoto mosaics which
will allow to query and analyse the results of all site-specific measurement
programmes is currently in preparation.
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| Please address requests and comments to Johannes Ries or Irene Marzolff |
- With kind assistance by WebTeam
IPG & uni ffm © 1999