2.2.2. Image Classification

After the pre-processing of the images, the standard images in the study periods were obtained (Figure 5) to perform classification by the support vector machine algorithm. Figure 6 showed the representative patterns of waterbodies in Landsat images. The areas in blue or black colors with a clear rectangular or square boundary are fish ponds, while the rivers that extends in strip shapes.

**Figure 5.** Pre-processed Landsat images for the 10 study periods.

**Figure 6.** Representative morphological features of fish ponds in Landsat images.

Some initial information can be obtained from these pre-processed images (Figure 5). Regarding image quality, it can be seen that the image quality of the early Landsat satellite images is somewhat lower than the recently acquired Landsat OLI images. It can be clearly seen that the early satellite images were fuzzier than the latest ones, indicating more noises in these images. In addition, it was observed that the urbanization in the GBA has experienced rapid development. The built-up area (in purple color) has substantially expanded.
