3. RESULT AND DISCUSSION
By interactive visual checking a set of threshold values for
Landsat 5 TM and Spot 5 HRG were established. The Table 3
shows the threshold values of band SWIR for all spectral
patterns.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
Spectral patterns Landsat 5 TM Spot 5 HRG
022222 3.0 45.0
222222 3.5 90.0
002222 N/A 40.0
002022 N/A 37.0
Table 3. Threshold values for spectral patterns in Landsat 5 TM
and Spot 5 HRG sensors
Based on the proposed algorithm and chosen threshold values
water extraction for the Landsat 5 TM and Spot 5 HRG had
been carried out. Figure 7 shows result of water body extraction
of Landsat 5 TM image and Figure 8 displays Spot 5 HRG
water body extraction. Water body filled by solid red colour
over 4, 3, 2 colour composites is showed on right sites in both
figures. The study area on Land sat 5 TM image is larger than
on the Spot 5 HRG. The study area includes Hanoi City and
surrounding area. Main water bodies are lakes, ponds, rivers and
canals. In colour composite SWIR-red, NIR-green and
Green-blue vegetation appears as green, urban including
housing, construction appear in purple colour. Clear water is
showed in dark blue and turbid water in cyan colour with
different level of brightness depending on sedimentation
contamination grades.
EHE
Figure 8. Water extraction by Spot 5 HRV image (left) and overlay on colour composite (right)
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