| Summary: | 碩士 === 國立中興大學 === 水土保持學系 === 87 === With the four periods of underdeveloped (1988), developing(1992), and fully developed(1994, 1999) spot images, this study analyzed the changes of the upper watershed of Feng-Shan stream because of its special development: golf court, freeway, play ground, mine zone, field, forest, orchard, tea field, and urban area.
This study investigated the changes of land use by method of comparing after classification, image overlapping and image differencing. In the method of comparing after classification, it classified the following images by means of un-supervised classification.
a. Primary images.
b. The images after topographic effect was corrected.
c. The primary images after the thematic map was cut.
d. The images after the topographic effect was corrected and thematic map was cut.
e. NDVI images.
The result was summarized as below:
1. The method of Comparing after classification: From the best to the least accuracy is d, b, c, and a.
2. Image overlapping: It is an efficient approach to find the changed location of land use. However, it is only a qualitative analysis and cannot quantitize the changed zone. We can therefore apply image overlapping method with quantitative analysis to monitor the changes and to select specimen. Through this way, not only the field work, but also the time and cost can be reduced.
3. Image differencing: The method can quickly find the changed area and quantitize, but the mistakes occur occasionally. By differentiating different periods at same area of single band pixel by pixel, and choosing suitable threshold value, we can quantitize the changed area. Nevertheless, the determination of threshold value affects the accuracy.
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