journal of forest science

Fig. 2. Flow chart illustrating the method for calculating the
values of skyline yarding distances from DEM
the gradient curve are checked in the process of cartographic
modelling which proved to be the main problem.
Skyline yarding distances model is a network model.
The possibility of laying out skyline yarding paths is
based on the following assumptions:
Fig. 3. Raster map of skyline yarding distances
1. The skyline tower in the cell of road and the tail spar in
the cell of a forest compartment are defined. If the distance
between the two above mentioned cells exceeds
the technological length of a cableway system, the layout
of skyline yarding path cannot be calculated. The
signal value which shows that the cell has not been
reached in skyline logging operations will be assigned
to the cell.
2. If the two cells under analysis can “see each other”
and the angle deviation of the line of sight from the
gradient curve does not exceed the user defined limit,
then the skyline yarding path lay-out will be possible
for those cells.
3. The skyline yarding distance will be calculated only
for the two cells which fulfil both mentioned conditions
(points 1, 2), but at the same time the calculated
distance is the shortest path from all considered combinations
which permit skyline yarding paths from the
terrain cell to road cells.
4. If the intervisibility conditions between two cells are
not fulfilled, a different signal value will be noted to
the cell, indicating that a tree jack must be used for
skyline extraction path.
The conditions described above must be satisfied to
identify skyline yarding paths which are laid out in the
direction of the gradient curve or along the permissible
angle from the gradient curve (parallel, not fanned out
routes).
ig. 2 illustrates a process flow diagram for calculating
skyline yarding distances in the ArcInfo TM environment.
The result of routines creating cartographic model
of skyline extraction distances can be seen in ig. 3.
UZZY REASONING INERENCE MECHANISM
AND PATH DISTANCE MODEL USED OR
LOCATING OREST HAULING ROADS
The system designed for laying out hauling roads has
to focus on identifying passing points on roads and is
based on the evaluation of yarding distances which were
modelled in the field. In the process of selecting passing
points, grade and distances between points and yarding
distances from existing roads are controlled by fuzzy reasoning
mechanism using linear functions. Inference rules
for fuzzy reasoning used in the proposed system were
described in YOSHIMURA (1997). The rules implemented
in this mechanism represent human thinking processes
based on an expert designer’s experience, skill and
knowledge of specific conditions used to locate forest
roads. The rules had to be adjusted for hauling road conditions
pertaining to Slovakia (the maximum gradient of
a hauling road is limited to 12%).
The inference rule equations are expressed as follows:
I x 1 is ‘Big’ THEN y 1 = –50x 1 (Very Small)
I x 2 is ‘Big’ THEN y 2 = –100x 2 (Very Small)
I x 1 is ‘Small or Medium’ and x 2 is ‘Medium or
Small’ and x 3 is ‘Big or Medium’ and x 4 is ‘Big or Medium’
J. FOR. SCI., 47, 2001 (7): 307–313 309