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4. REVISION OF FORESTRIAL MAPS BY
DIGITAL MONOPLOTTING
Verification and revision of forestrial maps based on
aerial images and orthophotos is considered as an ap-
propriate tool in forestry (Próbsting,1994). Even mono-
plotting procedures based on analogue images have
been introduced (Schneider, Bartl, 1994).
The proposed approach is purely digital and therefore
allows the forestry expert to interpret and record chan-
ges, damages or other phenomenas with high geometri-
cal accuracy by superimposition of image and vector
data on the screen of a workstation. Image enhancement
tools (contrast, brightness) or zoom functions may be
applied during the evaluation.
On the other side an efficient exchange of data between
the forest-GIS (SICAD) and the monoplotting system
(PHOCUS) isrequired. Within the project the exchange
procedure of digital forest data was realized first for the
'Forest-Management-Map', which is a product of the
forestrial GIS. At first, all elements of the forestrial map
have been implemented in the PHOCUS object code
table. Since PHOCUS manages and stores the objects
without their graphic representation, it was necessary to
adopt the graphic-code table and the related symbol
construction and execution tables in a way that an iden-
tical representation of all features under SICAD and
PHOCUS was achieved.
With the program package GDBPHO, developed by
Schubert & Partner, SICAD-datasets can be transferred
into the PHOCUS exchange data format PHODAT by
means ofa transfer table. Afterwards the data are stored
into the PHOCUS database and represented together
with the orthophoto. Now an efficient recording can be
done bya comfortable usershell, which offers all features
ofthe forestrial map on a screen menu.
In Figure 4 a section of a Forest-Management-Map is
presented under PHOCUS environment.
Figure 4 : Section of a forest management map during
map revision under PHOCUS environment
The data from the forestry GIS have been superimposed
to the digital orthophoto. Because of the colour-filled
areas of the map, the orthophoto is not visible in this
areas. Therefore an option is offered to clear the colour-
filled areas. The deletion of the colour-fill is nothing but
a different graphical representation. Each individual
areal object still can be identified correctly.
Also other forest maps like the ’site map’or ’slope lability
map’ were transferred into PHOCUS. These datasets
were imported from the GIS-System ARC/INFO.
5. DTM SUPPORTED MONOPLOTTING
The high quality DTM which was already used for digital
orthoimage generation is a valuable source during the
evaluation process with monoplotting. First of all it is
used to calculate the terrain height (z-coordinate) for
any point which is measured in the orthoimage. Further-
more it is the base for the calculation and on-line use of
different DTM products during monoplotting. For this
reason the user shell of PHOCUS-M has been modified
in order to allow the operator to derive the products
within one and the same environment.
As vector products contour lines and slope and aspect
information represented as arrows turned out to be
useful especially for forest sanitation projects in alpine
regions (see section 5). Figure 5 shows an example of an
orthoimage superimposed with contours and aspect ar-
rows. The length of the arrows represents the slope
value.
Figure 5: Orthoimage with superimposition of derived
contours and aspect arrows
Also products in raster format like colour-coded height-,
slope- and aspect-classes or as shaded relief repre-
sentation are offered. Usually these products are used
to pre-determine areas of interest (e.g. catchment areas
for soil erosion). These areas are digitized on the screen
and afterwards superimposed with the orthoimage for
planing restauration arrangements.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
