Land Use Dynamics from Multi-temporal Remotely Sensed Data: A Case Study Northern Thailand
2. Data and sources of data
The data are composed of:
- Satellite imagery: Landsat MSS (01-02-1977), Landsat TM (11-01-1989) and Landsat ETM+ (14-03-2000);
- Aerial photos in 1989, 1991 and 1996, scale 1:50,000;
- Field survey and GPS coordinate registration of land use samplings in April and May 2001;
- Semi-structured interview in May 2001 for land use history;
- Mae Song watershed GIS database established in 2000 by the author at the Geo-informatics and Space Technology Center (Northern region), Faculty of Social Sciences, Chiang Mai University.
Three Landsat satellite images were rectified to UTM coordinates using a topographic map of the area. The 1989 image was rectified an UTM topographic map, the remaining two were rectified to this image on an image-to-image basis. All image manipulation was made using the CHIPS (Copenhagen Image Processing System) software package (figure 1). Channel 1 in both the 1977 and 2000 image have some noises on the image. The 1977 image was polluted by repeated scan lines, whereas the signal in the 2000 channel one was obscured by haze, possibly smoke from vegetation fires during summer time of the North (Dontree et al., 2002). False color composite are
Then, all three dates of the aerial photos are converted to digital format using a scanner. The 1996 aerial photos are rectified to UTM coordinates referred from a topographic map. The 1989 and 1991 aerial photos are geocoded to the 1996 rectified photos by image to image method. All geometric rectifications are processed by IDRISI 32 Release 2.
Figure 1 Landsat satellite imageries of the study area