Wrong EVI values

Apps / Services
#1

Hello, i’m getting 0 to 250 tiff values when I run this Layer script in QGIS.
What should I add to get -1 to +1 values as index?
Regards

//VERSION=3

function evaluatePixel(samples) {
let val = 2.5 * (samples.B08 - samples.B04) / (samples.B08 + 6 * samples.B04 - 7.5 * samples.B02 + 1);
return [val, samples.dataMask];
}

function setup() {
return {
input: [{
bands: [
“B02”,
“B04”,
“B08”,
“dataMask”
]
}],
output: {
bands: 2
}
}
}

#2

Hi ihernandez,

to get values between -1 and 1 you need to specify sampleType: "FLOAT32". E.g.:

//VERSION=3

function evaluatePixel(samples) {
	let val = 2.5 * (samples.B08 - samples.B04) / (samples.B08 + 6 * samples.B04 - 7.5 * samples.B02 + 1);
	return [val, samples.dataMask];
}

function setup() {
	return {
		input: [{
			bands: [
				"B02",
				"B04",
				"B08",
				"dataMask"]
		}],
		output: {
			bands: 2, 
    		sampleType: "FLOAT32"
		}
	}
}

More info in the SH documentation: sampleType

I am not sure how exactly you are using this in Qgis. To get float values you might need to add a WCS layer.

#3

Thanks it worked! I work always with WMS and its fine. I don’t know whats the different between WCS and WMS. In QGIS I use the Plugin to search for images and download from there.
Regards. Jose