Hi, here my requesto to Sentinel2 data to compute NDVI index of a orchard:
{
"input": {
"bounds": {
"properties": {
"crs": "http: //www.opengis.net/def/crs/OGC/1.3/CRS84"
},
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
42.5979522,
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],
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],
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],
[
42.5970045,
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]
]
}
},
"data": [
{
"type": "sentinel-2-l2a",
"dataFilter": {
"timeRange": {
"from": "2023-06-03T00:00:00Z",
"to": "2023-06-06T23:59:59Z"
}
}
}
]
},
"output": {
"width": 4,
"height": 4,
"responses": [
{
"identifier": "default",
"format": {
"type": "image/tiff"
}
}
]
},
"evalscript": "function setup() {\n return {\n input: [{\n bands: [\n "B04",\n "B08",\n "dataMask"\n ]\n }],\n output: {\n bands: 1,\n sampleType: SampleType.FLOAT32\n }\n }\n }\n\n function evaluatePixel(samples) {\n let val = (samples.B08-samples.B04)/(samples.B08+samples.B04)\n //index(samples.B08, samples.B04);\n //val = Math.round((val+1)*127.5)\n return [val];\n }"
}
The code works, but I don’t know how to interpretate the data retrived:
(I used 4x4 pic size in order to make considerations easier)
[[[0.02797203 0.01792115 nan nan]
[0.01796407 0.0263789 0.02612827 0.02040816]
[0.02508961 0.01405152 0.01538462 0.02060606]
[0.01492537 0.01750292 0.0212766 nan]]]
I expect data from -1 to 1, but more precisely between 0 and 0.5-0.6
Can someone help me to understand how to interpretate these results or can tell me if there are any mistake?