尝试使用Javascript在谷歌地球引擎中编码时出错

Question

我得到了这个代码，但当我运行它给出错误信息

"L8"在此范围内未定义。在第11行在第30行

我使用的代码是这样的

var RGB_vis = {min: 0, max: 0.3, bands: ['B4', 'B3', 'B2']};
var filtered = L8
.filterDate('2019-01-01', '2019-12-31')
.filterBounds(geometry)
.sort('CLOUD_COVER', true);
var image = ee.Image(filtered.first());
Map.addLayer(image, RGB_vis,'RGB' );
// Compute the Normalized Difference Vegetation Index (NDVI).
var nir = image.select('B5');
var red = image.select('B4');
var ndvi = nir.subtract(red).divide(nir.add(red)).rename('NDVI');
// Display the result.
Map.centerObject(image, 9);
var ndviPara ={min: -1, max: 1, palette: ['blue', 'white', 'green']};
Map.addLayer(ndvi, ndviPara, 'NDVI image');

Answer 1

首先需要通过插入Landsat 8 ImageCollection:

来定义L8变量

var L8 = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
var RGB_vis = {min: 0, max: 0.3, bands: ['B4', 'B3', 'B2']};
var filtered = L8
.filterDate('2019-01-01', '2019-12-31')
.filterBounds(geometry)
.sort('CLOUD_COVER', true);
var image = ee.Image(filtered.first());
Map.addLayer(image, RGB_vis,'RGB' );
// Compute the Normalized Difference Vegetation Index (NDVI).
var nir = image.select('B5');
var red = image.select('B4');
var ndvi = nir.subtract(red).divide(nir.add(red)).rename('NDVI');
// Display the result.
Map.centerObject(image, 9);
var ndviPara ={min: -1, max: 1, palette: ['blue', 'white', 'green']};
Map.addLayer(ndvi, ndviPara, 'NDVI image');