6. APPLICATIONS AND EXPERIENCES
6.1 Revision of the Forest-Management-Map
The system was tested by foresters within map revision
projects in lowland and in highland. In a first step a high
quality orthoimage was generated using the hybrid data
structure of HIFI. Then the existing data set of the
Forest-Management-Map was extracted from the fo-
restry GIS (SICAD) and transferred into the PHOCUS
data base. After superimposition the operator was able
to detect the changes in the forest population by compa-
rison of the digital orthoimage and the original map.
Although only black and white images at a scale of
1:15000 were available for the testareas, it was possible
to recognize changes in forest stands parcels, tree stock
descriptions, homogeneity of population and age
structure.
With the use of colour infrared images interpretation is
more efficient , so that even the degree of damage could
have been determined. It is not possible to extract infor-
mation about the rejuvinescence of the population less
than 2m in height. As a fact of monoplotting of course
height of trees cannot be measured.
The changes were edited in the original data set in the
PHOCUSenvironment. PHOCUS offers a feature to set
a distinguishing tag on all objects which have been edited
or recorded during map revision so that only the revised
objects have to be transferred back to the forestry GIS
(SICAD).
A print-out of the revised map superimposed with the
orthoimage proved to be a very good "work map" for
verification in the field. After field verification the chan-
ges again were edited in the monoplotting environment.
This "three step approach" turned out to be adequate
and the acceptance by the foresters was quite good. Up
to now the revision of the forestrial maps is done by field
verification only, correcting the analogous maps. Al-
though field verification is still indispensable, the prepa-
ration for an efficient field work and the revision via
digital monoplotting is substantially easier. For example
the contours in the highlands were very useful during
field verification. Beyond that the forest population was
reliable identified from the digital orthophoto, therefore
the corrections in the field were reduced considerably.
6.2 Inventory by Spot Checks
Spot check inventory usually is carried out in the follo-
wing way: The area to be inventoried is covered with a
regular grid. Within a defined circle around the spot
check point all trees are registered with their type, crown
diameter, and damage class.
With the developed system it is possible to superimpose
the inventory grid and the investigation circles with the
orthoimage. Now the inventory can be performed easily
on the screen using the zoomed colour infrared orthoi-
mage (cf. Fig. 6). For field verification the combined
print-out of orthoimage and inventory grid is an excel.
lent tool to locate the position of the check spot in the
field and to verify the results on the spot. Especially in
the highlands the preliminary inventory map is very use-
ful to locate the check points. Different tests of this two
stage approach have proved to reduce the time consu-
ming investigation in the field remarkably.
Usually the inventory is repeated in regular time inter-
vals (e.g. annually). In this case, the former inventory can
be visualized on the orthoimage and changes of the state
of the individual trees and crowns can be detected and
revised correctly. A pure crown mapping by means of
the digital orthophoto also is possible.
Figure 6: A spot check for forest inventory
6.3 Sanitation of Protective Forests
Especially in alpine regions the forest is of great impor-
tance to protect settlements and traffic facilities from
avalanches or damages caused bysoil erosion. Therefore
an important field in forestry is monitoring and sanitati-
on of so called "protective forests". If the forest cannot
fulfil its natural function of protection, replanting or
man-made constructions have to be planned.
The digital monoplotting system was also tested for this
task. In a first step the DTM products contours, colour
coded slope and aspect maps were derived from the high
quality DTM. Since the superimposition of DTM raster
images causes an erasing of the orthoimage, a tool was
developed which allows the operator to vectorize the
areas of interest interactively by screen digitizing.
In figure 7 the orthophoto and the demarcated areas
obtained from a slope map are shown in superimpositi-
on. In a similar way colour coded exposition maps were
used. Now these "areas of danger" were investigated in
detail with the use ofthe orthoimage. Specific actions or
constructions have been planned directly on the screen
using a "toolbox" of the most common damming opera-
tions.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
tr Cc tc 9^ €5 (Jj m
€p
£o "Un a C)
V
S
