All analog data were transformed into digital data using
scanners. Data preparation and image processing were carried
out using the ERDAS Imagine software version 8.5. The aerial
photo image of each study area was geo-referenced with the topographic
map considering the UTM-Everest co-ordinates system
and thus registered with the satellite image. In addition, it is
necessary for aerial photographs to be joined together under
mosaic operation to cover the area of study while satellite images
were subset. Since this study emphasizes mangrove forest
edges, areas in the vicinity of the shoreline have been examined.
The visible bands of satellite data (RGB 3,2,1: true color
composite) were used for a first reconnaissance. Due to a relatively
low image quality, image enhancement technique was
employed to the aerial photograph of Ranong. Thereafter,
both aerial photographs and satellite images were classified
using unsupervised classification with 10 classes. Subsequently,
the subclasses were merged and recoded to three classes:
water, mangroves and mud. Finally, the classified aerial
photo image and satellite image were added (Panapitukkul
et al., 1998) by operation utility.