Google Earth Engine（GEE）——用填充后的Landsat7影像进行LST地表温度计算（C值转化为K值）

var GapFill = function(image) {
  var start = image.date().advance(-1, 'year');
  var end = image.date().advance(1, 'year');
  var fill = l7.filterDate(start, end).median();
  var regress = fill.addBands(image); 
  var regress = regress.select(regress.bandNames().sort());
  var fit = regress.reduceNeighborhood(ee.Reducer.linearFit().forEach(image.bandNames()), kernel, null, false);
  var offset = fit.select('.*_offset');
  var scale = fit.select('.*_scale');
  var scaled = fill.multiply(scale).add(offset);
  return image.unmask(scaled, true);
};

var point = 
    /* color: #98ff00 */
    /* shown: false */
    /* displayProperties: [
      {
        "type": "rectangle"
      }
    ] */
    ee.Geometry.Polygon(
        [[[71.92283798912835, 34.38383276176222],
          [71.92283798912835, 34.32147587459247],
          [72.0574205086596, 34.32147587459247],
          [72.0574205086596, 34.38383276176222]]], null, false);
Map.addLayer(point)
var cloudMaskL7 = function(image) {
  var qa = image.select('pixel_qa');
  var cloud = qa.bitwiseAnd(1 << 5)
                    .and(qa.bitwiseAnd(1 << 7))
                    .or(qa.bitwiseAnd(1 << 3));
  var mask2 = image.mask().reduce(ee.Reducer.min());
  return image.updateMask(cloud.not()).updateMask(mask2);
};
var l7 = ee.ImageCollection('LANDSAT/LE07/C01/T1_SR')
    .map(cloudMaskL7);
var kernelSize = 10;
var kernel = ee.Kernel.square(kernelSize * 30, 'meters', false);
var GapFill = function(image) {
  var start = image.date().advance(-1, 'year');
  var end = image.date().advance(1, 'year');
  var fill = l7.filterDate(start, end).median();
  var regress = fill.addBands(image); 
  var regress = regress.select(regress.bandNames().sort());
  var fit = regress.reduceNeighborhood(ee.Reducer.linearFit().forEach(image.bandNames()), kernel, null, false);
  var offset = fit.select('.*_offset');
  var scale = fit.select('.*_scale');
  var scaled = fill.multiply(scale).add(offset);
  return image.unmask(scaled, true);
};
// TESTING CODE
Map.centerObject(point, 11);
var check = ee.ImageCollection('LANDSAT/LE07/C01/T1_SR')
    .filterBounds(point)
    .filterDate('2004-01-01', '2004-12-31');
var checkImage = ee.Image(check.first());
var visParams = {bands: ['B4', 'B3', 'B2'], min: 200, max: 5500};
Map.addLayer(checkImage.clip(point), visParams, 'source');
// Test composite.
var checkStart = checkImage.date().advance(-1, 'year');
var checkEnd = checkImage.date().advance(1, 'year');
var composite = l7.filterDate(checkStart, checkEnd).median();
Map.addLayer(composite.clip(point), visParams, 'median');
// Rough implementation for comparison.
var replaced = checkImage.unmask(composite);
Map.addLayer(replaced.clip(point), visParams, 'simple');
// Fancy implementation.
var filled = ee.Image(check.map(GapFill).median());
Map.addLayer(filled.clip(point), visParams, 'filled');
//median
{
var ndvi = filled.normalizedDifference(['B4', 
'B3']).rename('NDVI');
var ndviParams = {min: -1, max: 1, palette: ['blue', 'white', 
'green']};
print(ndvi,'ndvi');
Map.addLayer(ndvi.clip(point), ndviParams, 'ndvi');
}
//select thermal band 10(with brightness tempereature), no calculation 
var thermal= filled.select('B6').multiply(0.1);
var b10Params = {min: 291.918, max: 302.382, palette: ['blue', 
'white', 'green']};
Map.addLayer(thermal.clip(point), b10Params, 'thermal');
// find the min and max of NDVI
{
var min = ee.Number(ndvi.reduceRegion({
reducer: ee.Reducer.min(),
geometry: point,
scale: 30,
maxPixels: 1e9
}).values().get(0));
print(min, 'min');
var max = ee.Number(ndvi.reduceRegion({
reducer: ee.Reducer.max(),
geometry: point,
scale: 30,
maxPixels: 1e9
}).values().get(0));
print(max, 'max')
}
//fractional vegetation
{
var fv =(ndvi.subtract(min).divide(max.subtract(min))).pow(ee.Number(2)).rename('FV'); 
print(fv, 'fv');
Map.addLayer(fv.clip(point));
}
//Emissivity
var a= ee.Number(0.004);
var b= ee.Number(0.986);
var EM=fv.multiply(a).add(b).rename('EMM');
var imageVisParam3 = {min: 0.9865619146722164, max:0.989699971371314};
Map.addLayer(EM.clip(point), imageVisParam3,'EMM');
//LST in Celsius Degree bring -273.15
//NB: In Kelvin don't bring -273.15
var LST = thermal.expression(
'(Tb/(1 + (0.00115* (Tb / 1.438))*log(Ep)))-273.15', {
 'Tb': thermal.select('B6'),
'Ep': EM.select('EMM')
}).rename('LST');
var viz =  {min: 16, max:37, palette: [
'040274', '040281', '0502a3', '0502b8', '0502ce', '0502e6',
'0602ff', '235cb1', '307ef3', '269db1', '30c8e2', '32d3ef',
'3be285', '3ff38f', '86e26f', '3ae237', 'b5e22e', 'd6e21f',
'fff705', 'ffd611', 'ffb613', 'ff8b13', 'ff6e08', 'ff500d',
'ff0000', 'de0101', 'c21301', 'a71001', '911003'
 ]}
Map.addLayer(LST.clip(point), viz, 'LST');