基于GEE计算年度植被覆盖度
1.植被覆盖度计算公式参考地理学报的《2001-华北地区植被覆盖度与干旱条件的相关分析》
2.代码
var roi=ee.FeatureCollection("users/xxxx/Mydistrict");function rmCloud(image) {var cloudShadowBitMask = (1 << 3);var cloudsBitMask = (1 << 5);var qa = image.select("pixel_qa")var mask = qa.bitwiseAnd(cloudShadowBitMask).eq(0).and(qa.bitwiseAnd(cloudsBitMask).eq(0));return image.updateMask(mask);}//merge bestNDVIvar bestNDVI=ee.ImageCollection("LANDSAT/LC08/C01/T1_SR").filterDate("-01-01","-12-31").filterBounds(roi).map(rmCloud).map(function(image){var ndvi=image.normalizedDifference(["B5","B4"]);return image.addBands(ndvi.rename("NDVI"))}).qualityMosaic("NDVI").clip(roi).select("NDVI");Map.centerObject(roi,8);Map.addLayer(bestNDVI,{},"bestNDVI");//calculate the 5% and 95% num of the imagevar num =bestNDVI.reduceRegion({reducer:ee.Reducer.percentile([5,95]),geometry:roi,scale:30,maxPixels:1e13});print("num",num);var min = ee.Number(num.get("NDVI_p5"));var max = ee.Number(num.get("NDVI_p95"));print("min",min);print("max",max)//quantile and combinevar greaterPart = bestNDVI.gt(max);var lessPart = bestNDVI.lt(min);var middlePart =ee.Image(1).subtract(greaterPart).subtract(lessPart);// get the middle part//var mask=bestNDVI.gt(mim).add(bestNDVI.lt(min));//var middlePart=bestNDVI.updateMask(mask);//calculate FVCvar tempf1=bestNDVI.subtract(min).divide(max.subtract(min));//ee.Image(constant): creat a constatnt imagevar FVC=ee.Image(1).multiply(greaterPart).add(ee.Image(0).multiply(lessPart)).add(tempf1.multiply(middlePart));Map.addLayer(FVC,{},"FVC");//导出⽂文件到Drive，名称为l8Img，分辨率30⽶米，区域是roi区域Export.image.toDrive({image: FVC,description: "fvc",fileNamePrefix: "fvc",folder: "xxxx",scale: 30,region: roi,maxPixels: 1e13});
