The code use for calculate annual EVI vegetation index in Google Earth Engine but there's a problem not define getEVI8
// Define Study Area -- MainProject
var west = 21.691531038847305;
var east = 21.691531038847305; //-103;
var north = 30.563767723564865;
var south = 30.563767723564865;
var resolution = 30;
var projection = "EPSG:5070"; //" "EPSG:4269"; // max 65336
var MainProject = ee.Geometry.Rectangle(west,north,east,south);
Map.addLayer(MainProject);
Map.setCenter(30.563767723564865, 21.691531038847305, 8);
//SATURATES MASK (L5/7)
var maskSaturate57 = function(image){
image = image.select('B1','B3', 'B4');
var mask = image.lt(10000).and(image.gte(0));
return image.updateMask(mask);
};
//SATURATES MASK (L8)
var maskSaturate8 = function(image){
image = image.select('B2','B4', 'B5');
var mask = image.lt(10000).and(image.gte(0));
return image.updateMask(mask);
};
//PIXEL MASK (L5/L7)
var maskPixels57 = function(image){
var pixel_qa = image.select('pixel_qa');
var mask = pixel_qa.eq(66);
return image.updateMask(mask); };
//PIXEL MASK (L8)
var maskPixels8 = function(image){
var pixel_qa = image.select('pixel_qa');
var mask = pixel_qa.eq(322);
return image.updateMask(mask);
};
/*For Landsat 5 and 7, the ‘sr_atmos_opacity’ band was used to find and mask hazy pixels.*/
//ATMOS OPACITY MASK (L5/L7) -to get rid of haze
var maskHaze = function(image){
//Select band and multiply by scaling factor
var atmos_qa = image.select('sr_atmos_opacity').multiply(0.0010);
//Mask for non-hazy pixels and remove fill vals
var mask = atmos_qa.lte(0.1).and(atmos_qa.gt(-9.9));
return image.updateMask(mask);
};
/*For Landsat 8’s aerosol band, this function was used to remove pixels labelled as hazy.*/
//AEROSOL MASK (L8)
var maskAerosol = function(image){
var aero_qa = image.select('sr_aerosol');
var mask = aero_qa.neq(194).and(aero_qa.neq(224)).and(aero_qa.neq(160)).and(aero_qa.neq( 130));
return image.updateMask(mask);
};
// EVI Functions
/*These 2 functions are used to calculate the NDVI for Landsat 5/7 and Landsat 8, respectively.*/
// For L5 and L7
var getEVI57 = function(image){
//Apply saturate function
image = maskSaturate8(image);
};
var evi = getEVI8.expression(
'2.5 * ((NIR-RED) / (NIR + 6 * RED - 7.5* BLUE +1))', {
NIR:getEVI57.select('B4'),
RED:getEVI57.select('B3'),
BLUE:getEVI57.select('B1')
});
//.rename('nd');
//return(evi);
// For L8
var getEVI8 = function(image){
//Apply saturate function
image = maskSaturate8(image);
};
var evi = getEVI8.expression(
'2.5 * ((NIR-RED) / (NIR + 6 * RED - 7.5* BLUE +1))', {
NIR:getEVI8.select('B5'),
RED:getEVI8.select('B4'),
BLUE:getEVI8.select('B2')
});
//.rename('nd');
//return(evi);
// Sensor calibration functions
//Coefficient Function (L5)
var applyCoefficientL5 = function(image){
var image_adjusted = image.select('evi').multiply(1.036);
return(image_adjusted);
}
//Coefficient Function (L8)
var applyCoefficientL8 = function(image){
var image_adjusted = image.select('evi').multiply(1.0863);
return(image_adjusted);
}
// Main function
var createEVI_Composite_ = function(){
//Set year range
var yearrangeStart = 1985;
var yearrangeStop = 2019;
// Moving into the loop, the next variables of importance are:
for(var loopYear = yearrangeStart; loopYear <= yearrangeStop; loopYear +=1){
//Set years date range
var start = ee.Date.fromYMD(loopYear, 1, 1);
var end = ee.Date.fromYMD(loopYear, 12, 31);
//Landsat 8
var l8 = ee.ImageCollection("LANDSAT/LC08/C01/T1_SR")
//Filter AOI (imported at the top)
.filterBounds(MainProject)
//July and August only
.filterDate(start, end)
//Filter CLOUD_COVER
.filterMetadata('CLOUD_COVER', 'less_than', 80)
//Apply Pixel Mask
.map(maskPixels8)
//Apply Aerosol Mask
.map(maskAerosol)
//Calculate EVI
.map(getEVI8)
//Apply Sensor Callibration Coefficient
.map(applyCoefficientL8);
//Landsat7
var l7 = ee.ImageCollection("LANDSAT/LE07/C01/T1_SR")
//Filter AOI (imported at the top)
.filterBounds(MainProject)
//July and August only
.filterDate(start, end)
//Filter CLOUD_COVER
.filterMetadata('CLOUD_COVER', 'less_than', 80)
//Apply Pixel Mask
.map(maskPixels57)
//Apply Haze Mask
.map(maskHaze)
//Calculate EVI
.map(getEVI57);
//Landsat5
var l5 = ee.ImageCollection("LANDSAT/LT05/C01/T1_SR")
//Filter AOI (imported at the top)
.filterBounds(MainProject)
//July and August only
.filterDate(start, end)
//Filter CLOUD_COVER
.filterMetadata('CLOUD_COVER', 'less_than', 80)
//Apply Pixel Mask
.map(maskPixels57)
//Apply Haze Mask
.map(maskHaze)
//Calculate EVI
.map(getEVI57)
//Apply Sensor Callibration Coefficient
.map(applyCoefficientL5);
//Merge collections
var mergedCollection = ee.ImageCollection(l8.merge(l7).merge(l5)).reduce(ee.Reducer.percentile([90]));
var finalOutput = mergedCollection.reduce(ee.Reducer.median()).clip(MainProject).rename(loopYear.toString());
Map.addLayer(finalOutput, {'min': 50,'max': [10000]},'EVI_Composite_'+loopYear, false);
//Generate filename for export
var filename = ("EVI_Composite_").concat(loopYear.toString());
Export.image.toDrive({
image: finalOutput,
description: filename,
scale: 30,
region: MainProject,
crs: projection,
maxPixels: 800000000
});
}
};
//-----------------------------------//
// 5. MAIN FUNCTION EXECUTION //
//-----------------------------------//
var comp = createEVIComposite();
