Change detection
The change detection through the use of remote sensing and GIS was applied to determine changes in the Ranong coastal landscape particularly along the Andaman Seacoast. Two dates of
LANDSAT - 5 TM images dataset (March 17, 2004 and December 30, 2004) were processed to highlight the feature of changes between images focusing on the area near the coastline which obviously changed after tsunami attacked Ranong coastal zone, Thailand. The geolink technique was applied to both images. This technique is an ideal for investigate the changes of coastal landscape which have a same geodetic datum, otherwise the geometric correction is needed. The images of FCC and TCC were used to examine the changes. There were 6 major areas located near the coast have been explored and found the changes (Figure 4).
The basic premise in using remote sensing for change detection is that the process can identify change between two or more dates (Shalaby and Tateishi, 2007). This study aimed to highlight the changes of coastal features such as sandy beaches, waterway and mangrove forest between two dates. The coastal areas with more mangrove forest have less damaged from tsunami than the coastal area without the mangroves. Comparison by section revealed that sections 2 and 5 have been damaged more than other sections (Figure 5). Both sections are existed with sandy beach patches before but since their areas have been changed consequently the waterway also changed. The sand particles from both sections moved into the mangroves ecosystem and changed mangrove soil surface properties.