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and Third Mesh code (2 digit numbers). Table 1
shows the size of the local area as referred to by
each code of the SLAMC.
Table.1 Size of SLAMC
Mesh code Size of the local area
latitude x longitude approximate
square area
First Mesh 40' x 60' 80km x 80km
Second Mesh 5. x 7.30" 10km x 10km
Third Mesh 90" x 45" 1km x 1km
Fourth Mesh 3.75" x 5.625" 126m x 125m
Fourth Mesh shown in Table 1 is not available
from the DNLI. This code was made by the au-
thors to describe in detail the landslide areas.
This procedure let us overlap different scale maps.
3. IMAGE ANALYSIS SYSTEM
3.1 Multi data display
To investigate the basic relations among DNLI,
NVI and digitized thematic map data, we con-
structed an Image-Map database system [4].
Third Mesh in DNLI has approximately 1 square
km. Elevation data and inclination angle data are
recorded by dividing this mesh into 4 rectangular
areas.
Landslide data needs more detailed information.
Therefore, we divided the local area specified by
the Third Mesh code into 64 rectangular areas to
establish the Fourth Mesh code. The size of the
Fourth Mesh code is about 125mx 125m.
On the other hand, the geological map we used
here is 1:100000 scale-map and so it is very diffi-
cult to digitize into 125m squares. Therefore, we
divided the Third Mesh into 4 rectangular areas.
The grid width of the digitized Geological Map
becomes about 500m. Figure 1 shows the frame-
work of our image analysis system which involves
DNLI and NVI. The sizes of No.1 to No.6 are
10 square km. This size corresponds to the Sec-
ond Mesh code in DNLI. The minimum mesh size
in each window has different sizes as mentioned
above.
Each minimum mesh size are
(1) NVI : 125m
(2) Elevation : 250m
(3) Inclination : 250m
(4) Geology : 500m
(5) Landslide : 125m
(6) Overlap : 125m
387
3.2 Single data display for wide area
Prepared data concerning the Image Analysis sys-
tem are all Second Mesh size,however, landslides
occur in wide areas, therefore we have to investi-
gate as expansively as possible.
Figure 2 and 3 shows the whole area and a speci-
fied area of NOTO district where landslides often
occur in all seasons. Figure 2 shows distribution
of elevation data in NOTO district. Figure 3 was
magnified. This single data display system can
show any optional 9 piece blocking or the whole
54 piece area in the Third Mesh code.
Figure 4 shows NVI data for whole area in the
NOTO district by using this system.
4. ANALYSIS OF LANDSLIDE AREAS
4.1 Statistics of Thematic Maps
We investigated the characteristics of thematic
maps by using the image analysis system to com-
bine NVI data and map data. Both the distri-
bution and the area of geology in each second
mesh were investigated. Figure 5 shows the rela-
tionship between the kind of geology and area of
WAJIMA district(second mesh). Figure 6 shows
the same relationship as figure 5 for all the sec-
ond mesh of the NOTO peninsula. As a re-
sult, we found that andesite lava and sedimen-
tal rock are most widely distributed in landslide
areas. Sandstone, mudstone and conglomerates
were also found in large distribution. It is well
known that sedimental rock and mudstone are
soft soil, so we can estimate that landslides will
generate in these areas. Figure 7 shows the rela-
tion between the inclination angle and the ratio
of landslide occurrences. The ratio of landslide
occurrences is the ratio of landslide area to total
area at the one inclination angle. This figure sug-
gested that most landslides in the NOTO district
occurred on gentle slopes more than steep slopes.
4.2 Overlapping
The objective of this study is to estimate the area
where landslides may occur in the near future. In
order to estimate successfully, we have to investi-
gate the characteristics of areas where landslides
occurred in the past. Thematic maps (landslide),
other maps and DNLI are overlapped. This pro-
cedure is conducted by the image analysis system.
One example of the WAJIMA region is as follow-
ing:
