LAI (Leaf Area Index)
//VERSION=3 (auto-converted from 2)
var degToRad = Math.PI / 180;
function evaluatePixelOrig(samples) {
var sample = samples[0];
var b03_norm = normalize(sample.B03, 0, 0.253061520471542);
var b04_norm = normalize(sample.B04, 0, 0.290393577911328);
var b05_norm = normalize(sample.B05, 0, 0.305398915248555);
var b06_norm = normalize(sample.B06, 0.006637972542253, 0.608900395797889);
var b07_norm = normalize(sample.B07, 0.013972727018939, 0.753827384322927);
var b8a_norm = normalize(sample.B8A, 0.026690138082061, 0.782011770669178);
var b11_norm = normalize(sample.B11, 0.016388074192258, 0.493761397883092);
var b12_norm = normalize(sample.B12, 0, 0.493025984460231);
var viewZen_norm = normalize(Math.cos(sample.viewZenithMean * degToRad), 0.918595400582046, 1);
var sunZen_norm = normalize(Math.cos(sample.sunZenithAngles * degToRad), 0.342022871159208, 0.936206429175402);
var relAzim_norm = Math.cos((sample.sunAzimuthAngles - sample.viewAzimuthMean) * degToRad)
var n1 = neuron1(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm);
var n2 = neuron2(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm);
var n3 = neuron3(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm);
var n4 = neuron4(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm);
var n5 = neuron5(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm);
var l2 = layer2(n1, n2, n3, n4, n5);
var lai = denormalize(l2, 0.000319182538301, 14.4675094548151);
return {
default: [lai / 3]
}
}
function neuron1(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm) {
var sum =
+ 4.96238030555279
- 0.023406878966470 * b03_norm
+ 0.921655164636366 * b04_norm
+ 0.135576544080099 * b05_norm
- 1.938331472397950 * b06_norm
- 3.342495816122680 * b07_norm
+ 0.902277648009576 * b8a_norm
+ 0.205363538258614 * b11_norm
- 0.040607844721716 * b12_norm
- 0.083196409727092 * viewZen_norm
+ 0.260029270773809 * sunZen_norm
+ 0.284761567218845 * relAzim_norm;
return tansig(sum);
}
function neuron2(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm) {
var sum =
+ 1.416008443981500
- 0.132555480856684 * b03_norm
- 0.139574837333540 * b04_norm
- 1.014606016898920 * b05_norm
- 1.330890038649270 * b06_norm
+ 0.031730624503341 * b07_norm
- 1.433583541317050 * b8a_norm
- 0.959637898574699 * b11_norm
+ 1.133115706551000 * b12_norm
+ 0.216603876541632 * viewZen_norm
+ 0.410652303762839 * sunZen_norm
+ 0.064760155543506 * relAzim_norm;
return tansig(sum);
}
function neuron3(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm) {
var sum =
+ 1.075897047213310
+ 0.086015977724868 * b03_norm
+ 0.616648776881434 * b04_norm
+ 0.678003876446556 * b05_norm
+ 0.141102398644968 * b06_norm
- 0.096682206883546 * b07_norm
- 1.128832638862200 * b8a_norm
+ 0.302189102741375 * b11_norm
+ 0.434494937299725 * b12_norm
- 0.021903699490589 * viewZen_norm
- 0.228492476802263 * sunZen_norm
- 0.039460537589826 * relAzim_norm;
return tansig(sum);
}
function neuron4(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm) {
var sum =
+ 1.533988264655420
- 0.109366593670404 * b03_norm
- 0.071046262972729 * b04_norm
+ 0.064582411478320 * b05_norm
+ 2.906325236823160 * b06_norm
- 0.673873108979163 * b07_norm
- 3.838051868280840 * b8a_norm
+ 1.695979344531530 * b11_norm
+ 0.046950296081713 * b12_norm
- 0.049709652688365 * viewZen_norm
+ 0.021829545430994 * sunZen_norm
+ 0.057483827104091 * relAzim_norm;
return tansig(sum);
}
function neuron5(b03_norm,b04_norm,b05_norm,b06_norm,b07_norm,b8a_norm,b11_norm,b12_norm, viewZen_norm,sunZen_norm,relAzim_norm) {
var sum =
+ 3.024115930757230
- 0.089939416159969 * b03_norm
+ 0.175395483106147 * b04_norm
- 0.081847329172620 * b05_norm
+ 2.219895367487790 * b06_norm
+ 1.713873975136850 * b07_norm
+ 0.713069186099534 * b8a_norm
+ 0.138970813499201 * b11_norm
- 0.060771761518025 * b12_norm
+ 0.124263341255473 * viewZen_norm
+ 0.210086140404351 * sunZen_norm
- 0.183878138700341 * relAzim_norm;
return tansig(sum);
}
function layer2(neuron1, neuron2, neuron3, neuron4, neuron5) {
var sum =
+ 1.096963107077220
- 1.500135489728730 * neuron1
- 0.096283269121503 * neuron2
- 0.194935930577094 * neuron3
- 0.352305895755591 * neuron4
+ 0.075107415847473 * neuron5;
return sum;
}
function normalize(unnormalized, min, max) {
return 2 * (unnormalized - min) / (max - min) - 1;
}
function denormalize(normalized, min, max) {
return 0.5 * (normalized + 1) * (max - min) + min;
}
function tansig(input) {
return 2 / (1 + Math.exp(-2 * input)) - 1;
}
function setup() {
return {
input: [{
bands: [
"B03",
"B04",
"B05",
"B06",
"B07",
"B8A",
"B11",
"B12",
"viewZenithMean",
"viewAzimuthMean",
"sunZenithAngles",
"sunAzimuthAngles"
]
}],
output: [
{
id: "default",
sampleType: "AUTO",
bands: 1
}
]
}
}
function evaluatePixel(sample, scene, metadata, customData, outputMetadata) {
const result = evaluatePixelOrig([sample], [scene], metadata, customData, outputMetadata);
return result[Object.keys(result)[0]];
}Evaluate and Visualize
General description of the script
LAI is a dimensionless index measuring the one-sided green leaf area over a unit of land (m^2 / m^2).
Note that the LAI script is as implemented in SNAP but without input and output validation! Input/output values which are suspect are not reported or changed. Most values, however, do not fall under this category. Visualized as an interval from 0-3. This can be adjusted in the evaluatePixel method.
Description of representative images
Leaf area index, Rome. Acquired on 08.10.2017.
