在GEE中,Landsat系列产品主要分为两类:一类是TOA产品(大气层顶反射率或表观反射率产品),另一类是SR产品(地表反射率产品)。
SR地表反射率产品
SR的去云主要是用QA波段来进行操作的,这种去云方法直接使用的是通过和QA质量波段做按位操作实现对像素值的筛选,掩膜掉云
云阴影、雪等像素,最终达到去云的目的。
代码
var roi = /* color: #0b4a8b */ee.Geometry.Polygon(
[[[115.22447911987308, 38.97207826950874],
[117.64147130737308, 39.07450027191289],
[117.55358068237308, 40.67633196985795],
[114.91686193237308, 40.576272152256934]]]);
Map.centerObject(roi, 7);
function rmCloud(image) {
//云阴影和云
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);
}
var rawImage = ee.Image("LANDSAT/LC08/C01/T1_SR/LC08_123032_20180118");
var visParams = {
bands: ['B4', 'B3', 'B2'],
min: 0,
max: 3000
};
print("rawImage", rawImage);
Map.addLayer(rawImage, visParams, "rawImage");
var cleanImage = rmCloud(rawImage);
print("cleanImage", cleanImage);
Map.addLayer(cleanImage, visParams, "cleanImage");
结果