Karst Desertification Investigation Base On ETM Image

The Southwest of China,where Karst Rock Desertification land lies in,is the karst rock area that distributing most wide and developing most intense in the world.The problems of Karst Rock Desertification and poverty in karst environment are not only the worldwide basic issues,but also a very important factor in close of association with the sustainable development of southwest area. The rocky desert is one of the four primary frail belts of ecological environment—Karst,Loess, Desert,Tundra—in the west of China,which causes regional ecological environment to worsen,the land productive force declining,the water resources is scarce and regional impoverished occurrence. It is important to control the Karst Rocky Desertification for ensuring the national ecological security, implement develop-the-west strategy,dwindle regional gap between rich and poor,maintain national unity and society harmonious.Only we master the present situation and reasons of Karst Rock Desertification,then explore effective countermeasures and models that can we prevent it successful for safeguard the healthy,fast,sustainable development society and economy of Nanchuan city.On the basis of remote sensing image and geographic information system,according to the classification rule which educed from different rock desertification degree have different vegetation fraction,slope,lithology and so on,this article extract the rock desertification information of Nanchuan city by using the method of expert classification which was provided by Erdas Imagine9.1. Compare with supervised classification,non-supervised classification and other traditional visual interprets,the method of expert classification can easy achieve higher accuracy.The ascertainment of Geometry correction and vegetation coverage Empirical Model will mainly effect the chart precision when use this method extracting the remote sensing picture information for drawing.Generally speaking geometry correction can minish the error when superpose the multiple source spatial information(slope,lithology,vegetation coverage and so on); When constructing the Empirical Model,more sample spots,nicer the Empirical Model will be,and higher the precision of result map will be,too. On the basis of interrelated theory and the environment condition of the Southwest karst rock area,study extent and anciently work experience,the investigations mostly adopt these work steps:1.Carry out the band selection and Pre-treatment to the selected remote sensing image;2.Extract the NDVI value and transform it into the vegetation coverage degree of work area by using Empirical Model method;3.Establish carbonate rocks distributing database of work area;4.Establish the work area of slope hierarchical database;5.Establish the accurate classification Threshold value of the rocky desertification;6.Establish the template of respective dealing picture by use the expert classifier;it is the keystone in this article;7.Carry out the data statistical analysis to the result in the GIS platform and examine the precision to the researched area;8.Discuss the effective countermeasure and pattern for The Karst Rocky Desertification control.The Karst Rocky Desertification of Nanchuan is the most serious in Chongqing city,we find out the actuality of Karst Rocky Desertification of Nanchuan city from the investigation based on the satellite remote sensing.There are 140.43km~2 including the Karst Rocky Desertification and the latent Karst Rocky Desertification,which occupies 5.38%of the national territory area of Nanchuan city and 11.62%of the carbonate rock total area;Among them,latent Karst Rocky Desertification and the mild Karst Rocky Desertification area is 109.52km~2,occupies 77.99%of the Karst Rocky Desertification region area.Therefore,emphases of Karst Rocky Desertification protection and cure should be put on the latent and mild Karst Rocky Desertification area,the Karst Rocky Desertification degree of which should be prevented from getting worse.