LEGEND
EH Extracted Area (Score over 77)
BH Londslide occurred already
Contour line
avis
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Ra BUN I2
NE TAN
Fig.4 Distribution of extraction area.
Gray area is area of getting score over 77. tt is a great
possible to find new landslide points in gray area.
3.3 Attempt to renew the landslide distribution
information
Fig. 4 shows the results of 3.2 including those
of already occurred landslide areas. But the
possibility that new landslide may occur is
considered at other than the areas where landslide
occurred already. Therefore, in extracting new
areas of landslide, we overlaid the landslide point
information extracted by the analysis mentioned in
the above. with raster . data of topographical
information (information in the form of image), and
extracted the areas on the display by visual
interpretation. We attempted to renew the landslide
point information by overlaying the new landslide
points thus extracted onto the already occurred
landslide areas.
4, Conclusion
We obtain the following findings through this
study.
(1) It is useful to introduce GIS to support the
renew of landslide distribution information which
needed much time and labor in the past, Tor. the
following reasons.
1) Simultaneous evaluation of factor information
2) Free retrieval of geographical information
3) Quantitative and rapid grasp of complicated
polygons.
(2): To add: weight to factor . information - in
evaluating the overlay result means to establish a
quantitative judgment standard.
(3) In this study, we used only the information
which has been arranged as plane information. Even
by using the plane information, it is possible for
us to obtain support information to specify the
landslide area by utilizing the various function of
GIS.
654
5. Epilogue
In this study, we discussed the application of
GIS ‘to the extraction of landslide points and to
the renewal of landslide distribution information.
GIS is effective for quantitatively analyze the
geographical information which expands over a wide
area and which has complicated shape. The
effectiveness of GIS will become higher as there
will be more advancement in the study of spatial
analysis method such as pattern recognition.
Lastly, the following matters are pointed out as
the future problems:
(1) It is necessary to introduce objective and
quantitative method in making judgment for
attribute information. For this purpose, it is
desirable to establish the analysis method Jointly
using the statistical method such as quantity
theory.
(2) It takes much time and labor to construct the
database. When the future of GIS is considered, it
should be urgent to improve the efficiency of data
acquisition.
Bibliography
S. Akabane, H. Kato: Geology of Takada-seibu
district, with geological sheet map at 1:50000,
Geology Survaey Japan, pp. 78-82 (1989)
The Public. Works Research! Institution, Niigata
Institution: Landslide Distribution Map (1:50000)
(1969)
M. Setojima, K. Shiraishi and M. Mori: Extraction
of landslide areas using SPOT data and updating of
landslide distribution map, Journal of Japan
Society of Photogrametry and Remote Sensing, Vol.
30, No. :3, pp. /-15:01991)
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