Geography Reference
In-Depth Information
8
<
0,
x ¼
0
x
100
, 0
<
x
100
μ
B
ðÞ¼
ð
5
Þ
:
1,
x
>
100
where
x
is the distance from the feature boundaries. The crossover point is at
50 m.
Terrain slope
. The slope was computed from the elevation data and reclassified.
The linear membership function for terrain slope (S) can be defined as
8
<
1,
x
6
8
x
2
μ
S
ðÞ¼
ð
6
Þ
, 6
<
x
8
:
x
>
0,
8
where
x
is a slope in degrees. The crossover point is at 7
.
All the individual results were then overlaid. To visualize the level of suitability
of particular parts of the terrain for landing in a simple and illustrative way, the
military categories for the Cross-Country Mobility—
No Go
,
Slow Go
and
Go
—can
be used. As these classes are relatively broad, the more detailed classification was
applied. The membership function values of 0.2, 0.4, 0.6, and 0.8 were used to
create five classes of suitability for landing which were labelled as
Not Suitable
,
Very Limiting
,
Limiting
,
Acceptable
, and
Suitable
(see Table
1
and the example in
Fig.
1
).
Results and Discussion
The outputs of overlaying the individual results of both crisp and fuzzy sets are
showed in Fig.
1
. The example of the crisp set analysis on the left shows parts of the
terrain not suitable for landing of helicopters in black (i.e. red in the colour version)
and parts suitable for landing in gray (i.e. dark green). The example of the fuzzy set
analysis on the right shows the categories of the terrain divided according suitability
of landing. The results of the crisp set analysis show simple and clear division of the
terrain, but considering the features entering the analysis such as forests or built-up
areas we know that in reality they do not have crisp boundaries. Therefore the
boundaries between the parts of the terrain labelled as suitable or not suitable for
landing might not be fully representative.
Applying the fuzzy sets enables to improve the quality and reliability of the
analysis. It enables to identify highly convenient parts of the terrain that may be
used as the HLS and to leave the possibility still to use certain areas when accepting
a certain risk in relation to a particular feature. It can also eliminate a number of
locations that would be necessary to verify in the terrain when searching for the
