The Study Of Vegetation Coverage Modeling And Dynamic Changes In Miyun County

The vegetation coverage is a symbol of the measure vegetation growth status, and also the basis for many scientific research data, there are many ways to measure vegetation coverage, for example, there are surface measurement and use remote sensing estimation method, each method has its respective advantages and disadvantages, based on a series of survey data of Miyun County in the year of2011and the landsat series of satellite remote sensing images, this thesis adopts three methods to calculate the vegetation coverage of Miyun County. The first method is modeling based on vegetation index-NDVI with the model precision of74.23%; the second method is to do regression modeling analysis by extracting the relevant GIS factor and RS factor with the model accuracy of83.55%; the third one is to do modeling of vegetation coverage by adopting method of pixel dichotomy with the model accuracy of89.81%. the first two methods require the establishment of a large number of based on field investigation data, it is not easy to promote and application; latter method is based on remote sensing data sources, data source more readily available and easy application.For the purpose of analyzing the dynamic changes of vegetation coverage in Miyun County, three periods of the landsat satellite images of Miyun County are selected. The first is to calculate the dynamic changes of vegetation coverage of Miyun County by using a combination of vegetation index-NDVI and pseudo-color synthetic principle. The results show that during this period,3.70%of the water area has not changed,33.25%of the area has stable vegetation coverage,63.05%of the area has unstable vegetation coverage. The second is to do a classified statistics of the vegetation coverage in different slope, aspect and altitude by using pixel dichotomy and decision tree classification method so that the dynamic changes of vegetation coverage under different geographical conditions in Miyun County can be obtained. The results show that the vegetation coverage of Miyun County during this period has a overall downward trend,0<=Fc<0.5, the vegetation coverage is rising,0.5<=FC<1, the vegetation coverage is decreasing; within the same grade of vegetation coverage, the dynamic change of the area with theslope of less than20°is larger than the area with the slope greater than20°; aspect has no significant effect on the vegetation coverage; vegetation coverage is decreasing with the increasing of altitude, within the same grade of vegetation coverage, the vegetation coverage at an altitude of0<Elevation<=200,200<Elevation<=500has a larger proportion, but due to the human factors, this area has a largest dynamic change of vegetation coverage.