我想将landsat时间序列的ndvi值作为特征收集,以导出CSV中的长格式表。我使用汉森全球森林变化数据集和Landsat 7 Time系列。全球森林变化数据集将转换为特征集,以指定感兴趣的领域。Landsat 7时间序列用于获取NDVI值随着时间的流逝。
将Landsat NDVI时间序列转换为特征集合后,不出现NDVI值。将时间序列转换为仅三胞胎的"图像ID"one_answers" timemillis"。我已经检查了数据类型(现在INT16)和投影(EPSG:32638)。
我将感谢任何帮助。我错过了什么吗?
var lossImage = ee.Image('UMD/hansen/global_forest_change_2017_v1_5')
.select('lossyear')
.clip(geometry);
var datamask = ee.Image('UMD/hansen/global_forest_change_2017_v1_5')
.select('datamask')
.clip(geometry);
// specifying int16 and EPSG equivalent to landsat
var noloss = lossImage
.updateMask(lossImage.eq(0).and(datamask.eq(1)))
.int16()
.reproject('EPSG:32638', null, 30);
// create feat. collection to reduce regions of Landsat time series
var noloss_v = noloss.reduceToVectors({
reducer: ee.Reducer.countEvery(),
geometry: geometry,
scale: scale
});
//// functions for Landsat
var addNDVI = function(image) {
var ndvi = image.normalizedDifference(['B4', 'B3'])
.rename('NDVI').int16();
return image.addBands(ndvi);
};
var LS7 = ee.ImageCollection('LANDSAT/LE07/C01/T1_RT_TOA')
.filterBounds(geometry)
.filterDate('2005-01-01', '2015-12-31')
.map(addNDVI)
.select('NDVI');
//// Export LS NDVI
var triplets = LS7.map(function(image) {
return image.reduceRegions({
collection: noloss_v.select('system:index'),
reducer: ee.Reducer.mean().setOutputs(image.bandNames()),
scale: 30,
}).map(function(feature) {
return feature.set({
'imageID': image.id(),
'timeMillis': image.get('system:time_start')
});});
}).flatten();
我找到了缺失命令:减少后,必须使用" .filter(ee.filter.neq('ndvi',null))过滤0值"
var triplets = LS7.map(function(image){
return image.reduceRegions({
collection: noloss_v.select('system:index'),
reducer: ee.Reducer.mean().setOutputs(image.bandNames()),
scale: 30,
}).filter(ee.Filter.neq('NDVI', null))
.map(function(feature) {
return feature.set({
'imageID': image.id(),
'timeMillis': image.get('system:time_start')
});
});
}).flatten();