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Digital Image Processing 1
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Land conditional analysis for flood disaster combining raster / vector data
Method used for analysis
Multi dimensional and holistic approaches are needed in this study. We chose the following 2 methods for the analysis.
- Over laying various images representing land conditions
- to prepare various geographic information for flooded area and
- to overlay pixel by pixel, in order to extract worried area.
- Combination of Raster/Vector information
-analyze the features of highly worried areas, chosen by the analysis (1), combining raster and vector information, mainly that of social information.
Extracting worried areas through overlaying image(raster)information
- General
We chose approx. 30,000 ha of Kokai River and Kinu River basin. We used Landsat TM data, path/Row 107/35 of 23-Jan-1985 (CCT) and of 06-Auyg-1986
(False color photo). Procedures are followings.
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Land over classification: Using TM data before the flood, extracting 30 x 30 km area, and resample them into pixel size of 30 meter. Classification is made using geocoded 6 bands (excluding band-6). Classes are Rice field, Field, grassland, village, water zone, etc.
- Extracting flooded zone: After digitizing TM false color photo after the flood, Gooding it, then conducting level slicing with its blue data (TM Band-2)to extract flooded zone.
(photo-1)
Photo-1 Extraction of flooded zone
- Input of land Conditional Information: Based on Topographical Map and Land Condition Map, we input land form classification, slope classification, relative height, in order to establish Image Database. Each pixel is formed as 30x 30 meter, in order to correspond 1to 1with TM data.
- Analysis of flooded zone: Correlation was analyzed between flood realities and land conditions, overlaying pixel based land coverage information and land conditional information, which have been extracted from Landsite TM data, for the flooded zone.
- Extracting highly worried areas: Taking the results of (4) and already existing data into account, the importance of each land conditional categories was defined. Flood worriness classification for the entire basin was estimated based on this analysis.
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