I want to generate a NDWI chart, but I get this error:
Error generating chart: No features contain non-null values of "system:time_start".
enter code here
var L8 = ee.ImageCollection("LANDSAT/LC08/C02/T1_RT_TOA")
.filterDate('2021-01-01', '2021-12-31')
.filterBounds(VolRn)
.filterMetadata('CLOUD_COVER', 'less_than', 1.5)
.mean()
.clip(VolRn);
var green = L8.select('B3');
var nir = L8.select('B5');
var ndwi = green.subtract(nir).divide(green.add(nir)).rename('NDWI');
var ndwiParams = {
min: -1,
max: 1,
palette: ['green', 'white', 'blue']
};
var ndwiMasked = ndwi.updateMask(ndwi.gte(0.001))
Map.setCenter(44.5858, 48.8047, 7);
Map.addLayer(ndwi, ndwiParams, 'NDWI image');
var options = {
title: 'Landsat Spectral Indexes',
hAxis: {title: 'Date'},
vAxis: {title: 'Value'},
lineWidth: 1,
maxPixels: 1e9,
series: {
0: {color: 'blue'}, // NDWI
}};
print(Chart.image.series(ndwi, VolRn, ee.Reducer.mean(), 200).setOptions(options));
enter code here
Can you please explain what this error is and how to fix it.
I am completely new to GEE and can't find information about this error.
I will be very grateful
Related
I am trying to run the following code to extract the change map using the Land Trendr algorithm in Google Earth Engine. Everything seems to be running fine when I use a point as my area of interest, but once I try to use a polygon as my aoi file it throws me an error. I am attaching my code here :
//##########################################################################################
// START INPUTS
//##########################################################################################
// define collection parameters
var startYear = 1985;
var endYear = 2017;
var startDay = '06-20';
var endDay = '09-20';
//var aoi = ee.Geometry.Point(-122.8848, 43.7929);
var coords = ([70.9361058400289,28.387332974875402],
[83.5044652150289,28.387332974875402],
[83.5044652150289,37.305336609850876],
[70.9361058400289,37.305336609850876],
[70.9361058400289,28.387332974875402]);
var aoi = ee.Geometry.Polygon(coords);
var index = 'NBR';
var maskThese = ['cloud', 'shadow', 'snow', 'water'];
// define landtrendr parameters
var runParams = {
maxSegments: 6,
spikeThreshold: 0.9,
vertexCountOvershoot: 3,
preventOneYearRecovery: true,
recoveryThreshold: 0.25,
pvalThreshold: 0.05,
bestModelProportion: 0.75,
minObservationsNeeded: 6
};
// define change parameters
var changeParams = {
delta: 'loss',
sort: 'greatest',
year: {checked:false, start:2000, end:2010},
mag: {checked:true, value:200, operator: '\>', dsnr:false},
dur: {checked:true, value:4, operator: '\<'},
preval: {checked:true, value:300, operator: '\>'},
mmu: {checked:true, value:11},
};
//##########################################################################################
// END INPUTS
//##########################################################################################
// load the LandTrendr.js module
var ltgee = require('users/emaprlab/public:Modules/LandTrendr.js');
// add index to changeParams object
changeParams.index = index;
// run landtrendr
var lt = ltgee.runLT(startYear, endYear, startDay, endDay, aoi, index, [], runParams, maskThese);
// get the change map layers
var changeImg = ltgee.getChangeMap(lt, changeParams);
// set visualization dictionaries
var palette = ['#9400D3', '#4B0082', '#0000FF', '#00FF00', '#FFFF00', '#FF7F00', '#FF0000'];
var yodVizParms = {
min: startYear,
max: endYear,
palette: palette
};
var magVizParms = {
min: 200,
max: 800,
palette: palette
};
// display the change attribute map - note that there are other layers - print changeImg to console to see
Map.centerObject(aoi, 11);
Map.addLayer(changeImg.select(['mag']), magVizParms, 'Magnitude of Change');
Map.addLayer(changeImg.select(['yod']), yodVizParms, 'Year of Detection');
// export change data to google drive
var region = aoi.buffer(1000).bounds();
var exportImg = changeImg.clip(region).unmask(0).short();
Export.image.toDrive(
{image: exportImg,description: 'lt-gee_disturbance_map',
folder: 'lt-gee_disturbance_map',
fileNamePrefix: 'lt-gee_disturbance_map',
region: region,
scale: 30,
crs: 'EPSG:5070',
maxPixels: 1e13});
It is throwing an error: Line 75: GeometryConstructors.Polygon: LinearRing requires at least 3 points. I am not sure what I am doing wrong here. Thank you for your help.
my goal is to create a csv file from the data that is chosen between dates. This was the code that I used for creating the NDWI values. I want to export that data with date so that I can create a graph from time series of NDWI - date. But I could not found how, any help is appreciated, thanks.
Map.centerObject(areaOfInterest);
Map.addLayer(areaOfInterest);
var startDate = '2018-07-01';
var endDate = '2018-07-31';
var sentinelImageCollection = ee.ImageCollection('COPERNICUS/S2')
.filterBounds(areaOfInterest)
.filterDate(startDate, endDate);
print("Number of images = ", sentinelImageCollection.size());
// We select the image with the smallest cloudy pixel percentage
var sentinelImage = sentinelImageCollection.sort('CLOUDY_PIXEL_PERCENTAGE')
.first()
.clip(areaOfInterest);
print("Sentinel image taken at = ", sentinelImage.date());
// Visualize using RGB
Map.addLayer(sentinelImage, {min: 0.0, max: 2000, bands: ['B4', 'B3', 'B2']}, 'RGB');
// Visualize using NDWI
var ndwi = sentinelImage.normalizedDifference(['B3', 'B8']).rename('NDWI');
Map.addLayer(ndwi, {palette: ['red', 'yellow', 'green', 'cyan', 'blue']}, 'NDWI');
// Calculate the area of our region of interest
var aoiArea = ee.Image.pixelArea().divide(1e6).reduceRegion({
reducer: ee.Reducer.sum(),
geometry: areaOfInterest,
scale: 10,
}).get('area');
print('AOI area (km2):', aoiArea);
// Create NDWI mask
var ndwiThreshold = ndwi.gte(0.0);
var ndwiMask = ndwiThreshold.updateMask(ndwiThreshold);
Map.addLayer(ndwiThreshold, {palette:['black','white']}, 'NDWI Binary Mask');
Map.addLayer(ndwiMask, {palette:['blue']}, 'NDWI Mask');
// We can now calculate the masked areas pixel area
var ndwiPixelArea = ee.Image.pixelArea().addBands(ndwiMask.select('NDWI')).divide(1e6).reduceRegion({
reducer: ee.Reducer.sum().group(1),
geometry: areaOfInterest,
scale: 10,
bestEffort: true
});
var list = ee.List(ee.Dictionary(ndwiPixelArea).get('groups'));
var group0 = ee.Dictionary(list.get(0));
var ndwiWaterArea = ee.Number(group0.get('sum')).float();
print("Water area (km2):", ndwiWaterArea);
I'm trying to add polynomial regression line to my google trends live graph but it does not work properly:
as you can see the polynomial regression trendline is not fitting the data points properly (it's straight trendline and not a polynomial trendline).
My code is:
google.charts.load("current", {packages:["corechart"]});
google.charts.setOnLoadCallback(drawChart);
function drawChart() {
var data = new google.visualization.DataTable();
data.addColumn('datetime', 'Time of Day');
data.addColumn('number', 'Depth');
var options = {
title: 'graph',
legend: 'none',
crosshair: { trigger: 'both', orientation: 'both' },
trendlines: {
0: {
type: 'polynomial',
degree: 3,
visibleInLegend: true,
}
},
hAxis: {
viewWindow: {
min: new Date(),
}
},
vAxis: {
viewWindow: {
min: 0,
max: 100
}
}
};
var chart = new google.visualization.ScatterChart(document.getElementById('chart'));
chart.draw(data, options);
var interval = setInterval(function() {
var time = new Date();
data.addRow([time, newValue])
chart.draw(data, options);
}, 10);
I am trying to conduct a lulc classification on google earth engine using landsat5 data for 2000, but every time it is showing me the error:
image.select(bands).sampleRegions is not a function
var shp = ee.FeatureCollection(mws)
Map.addLayer(shp, {}, 'My Polygon')
var pol = ee.FeatureCollection(poly2000)
Map.addLayer(pol, {} )
//landcover for 2000//
var dataset = ee.ImageCollection("LANDSAT/LT05/C01/T1_TOA")
.filterBounds(roi1)
.filterDate('2000-01-01', '2000-01-31')
.map(function(image){return image.clip(mws)});
var trueColor432 = dataset.select(['B4', 'B3', 'B2']);
var trueColor432Vis = {};
Map.setCenter(88.41713038056656,26.861987108179317);
Map.addLayer(trueColor432, trueColor432Vis, 'True Color (432)');
var image = trueColor432;
// merging sample points together
var landcover = forest.merge(water).merge(clearing).merge(built_up);
print(landcover);
// selecting bands
var bands= ['B2','B3','B4'];
//sampling the input imagery to get a featurecollection of a training data
var training = image.select(bands).sampleRegions({
collection: landcover,
properties: ['landcover'],
scale: 30
});
//training the classifier
var classifier= ee.Classifier.svm().train({
features: training,
classProperty : 'landcover',
inputProperties: bands
});
//classifying the input imagery
var classified= image.select(bands).classify(classifier);
sampleRegions samples the pixels of an image: https://developers.google.com/earth-engine/apidocs/ee-image-sampleregions
Maybe adding .toBands() works?
var training = image.toBands().select(bands).sampleRegions({
collection: landcover,
properties: ['landcover'],
scale: 30
});
I am having issues rotating my symbol around a specific pivot point.
Here is my code :
var path_tank_left_track = new Path({
segments: [[0,0], [10, 0], [10,40], [0,40]], strokeColor: 'black',
closed: true
});
var path_tank_right_track = new Path({
segments: [[40,0], [50, 0], [50,40], [40,40]], strokeColor: 'black',
closed: true
});
var path_tank_body = new Path({
segments: [[10,5], [40,5], [40,35], [10,35]], strokeColor: 'black',
closed: true
});
var path_tank_gun = new Path({
segments: [[23,15], [23,0], [27, 0], [27, 15]],
strokeColor: 'black',
pivot: [25,15],
name: 'gun'
});
var path_arena_separation = new Path(new Point(view.size.width/2,0),
new Point(view.size.width/2, view.size.height));
path_arena_separation.strokeColor = 'black';
path_arena_separation.closed = true;
var whole_tank = new Group();
whole_tank.addChild(path_tank_left_track);
whole tank.addChild(new Point(5,20)); // trying to add the middle of the left track pivot point
whole_tank.addChild(path_tank_body);
whole_tank.addChild(path_tank_right_track);
whole tank.addChild(new Point(50,20)); // trying to add the middle of the right track pivot point
whole_tank.addChild(path_tank_gun);
// Create a symbol definition from the path:
var definition = new SymbolDefinition(whole_tank);
var instance1 = definition.place();
instance1.position = new Point(view.size.width/4, view.size.height/2);
var instance2 = definition.place();
instance2.position = new Point(3*view.size.width/4, view.size.height/2);
function onFrame(event) {
instance1.rotate(1, instance1.definition.item.children[1]);
}
As you can see, at the onFrame function, I'm trying to rotate the instance by 1 degree every frame around the point I created earlier. But I get an error saying the item_remove is not a function in the paper-full.js.
I'm confused, I tried to create a path with a single point and add it to the group but it did not let me.
If I modify the code to make the gun rotate on it's pivot instead, it does work :
function onFrame(event) {
instance1.definition.item.children['gun'].rotate(1, instance1.definition.item.children['gun'].pivot);
}
The gun does rotate around the proper pivot and the pivot stays attached to the symbol even if the symbol moves around. How could I achieve that behavior but turning the whole tank around a specific point relative to the center of the tank?
Thank you for your help, let me know if I should include more detail.
Your code is crashing because you try to add a point (and not a path containing a single point as you seems to be trying to) as a group child, which is not what API expects.
To create a path containing a single point, you have to do this:
var path = new Path(new Point(x,y));
But I think the idea of adding a single point path as a child to later retrieve its position to use it as a pivot point is wrong in your case.
The fact that you are creating each tank as a Symbol implies that you won't have access to its own children.
You can instead, before placing your symbols, store 2 vectors: one from center to left and one from center to right. They will later help you calculating left / right track positions.
Here is a Sketch adapted from your code, demonstrating this.
var path_tank_left_track = new Path({
segments : [ [ 0, 0 ], [ 10, 0 ], [ 10, 40 ], [ 0, 40 ] ],
strokeColor: 'black',
closed : true
});
var path_tank_right_track = new Path({
segments : [ [ 40, 0 ], [ 50, 0 ], [ 50, 40 ], [ 40, 40 ] ],
strokeColor: 'black',
closed : true
});
var path_tank_body = new Path({
segments : [ [ 10, 5 ], [ 40, 5 ], [ 40, 35 ], [ 10, 35 ] ],
strokeColor: 'black',
closed : true
});
var path_tank_gun = new Path({
segments : [ [ 23, 15 ], [ 23, 0 ], [ 27, 0 ], [ 27, 15 ] ],
strokeColor: 'black',
pivot : [ 25, 15 ],
name : 'gun'
});
var path_arena_separation = new Path(new Point(view.size.width / 2, 0), new Point(view.size.width / 2, view.size.height));
path_arena_separation.strokeColor = 'black';
path_arena_separation.closed = true;
var whole_tank = new Group();
whole_tank.addChild(path_tank_left_track);
whole_tank.addChild(path_tank_left_track);
whole_tank.addChild(path_tank_body);
whole_tank.addChild(path_tank_right_track);
whole_tank.addChild(path_tank_gun);
// store vectors from bounds center to tracks middle points
var tankCenter = whole_tank.bounds.center;
var leftTrackCenter = new Point(5, 20);
var rightTrackCenter = new Point(50, 20);
var leftVector = leftTrackCenter - tankCenter;
var rightVector = rightTrackCenter - tankCenter;
// Create a symbol definition from the path:
var definition = new SymbolDefinition(whole_tank);
var instance1 = definition.place();
instance1.position = new Point(view.size.width / 4, view.size.height / 2);
var instance2 = definition.place();
instance2.position = new Point(3 * view.size.width / 4, view.size.height / 2);
function onFrame(event)
{
// calculate pivot point position
// first we rotate vector accordingly to instance current rotation
var rotatedVector = rightVector.rotate(instance1.rotation);
// then we add it to current tank center
var point = instance1.bounds.center + rotatedVector;
// turn right
instance1.rotate(1, point);
}