Überwachte Klassifizierung mit Google Earth Engine

Question

Für eine Klassifizierung des Cerrado (eine Region in Brasilien) habe ich eine überwachte Klassifizierung mit der Google Earth Engine gewählt. Beim Ausführen des Skripts erscheint eine Fehlermeldung in der Konsole: "classified: Layer error: Eigenschaft 'agriculture' des Features '0_0' fehlt." Dies scheint nicht das Problem für meine anderen Klassen (Stadt und Wald) zu sein, während ich genau dasselbe mache.

Stadt, Landwirtschaft und Wald sind mit dem Polygonwerkzeug gezeichnete Polygone. Landsat ist das Bild, das ich klassifizieren möchte. Goias ist die Region, auf die ich mich konzentriere.

Was bedeutet dieses Merkmal '0_0'?

var forest = /* color: #0b4a8b */ee.Geometry.MultiPolygon(
 
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      [-50.90682506561279, -17.96909871332269]]]]), 
 
    goias = /* color: #ffc82d */ee.Geometry.Polygon(
 
     [[[-53.89773987402128, -17.737335150077946], 
 
      [-53.21656208374657, -18.780701454086767], 
 
      [-50.93127514381945, -19.71426205863078], 
 
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      [-52.07001767927636, -15.322314089978098], 
 
      [-52.44591109792566, -15.65224412638864]]]), 
 
    city = /* color: #00ffff */ee.Geometry.MultiPolygon(
 
     [[[[-47.92356491088867, -15.824128602644778], 
 
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      [-49.323463439941406, -16.64013669096455], 
 
      [-49.34440612792969, -16.652307275281608]]]]), 
 
    image = ee.ImageCollection("LANDSAT/LC8_SR"), 
 
    agriculture = /* color: #d63000 */ee.Geometry.MultiPolygon(
 
     [[[[-45.955810546875, -14.076641147746095], 
 
      [-45.924224853515625, -14.061988097202269], 
 
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      [-48.278045654296875, -16.479217790217742]]]]); 
 
      
 
var bands = ['B2','B3','B4','B5','B6','B7']; 
 

 
var cloudy_water_landsat = ee.ImageCollection('LANDSAT/LC8_SR') 
 
    .filterBounds(goias) 
 
    .filterDate('2016-06-01', '2016-07-10') 
 
    .median() 
 
    .set('SENSOR_ID', 'OLI_TIRS'); 
 

 
var datamask = cloudy_water_landsat.select('cfmask_conf'); 
 
var mask = datamask.eq(1); 
 
var water_landsat = cloudy_water_landsat.updateMask(mask); 
 

 
var datawater = water_landsat.select('cfmask'); 
 
var not_water = datawater.eq(1); 
 
var water = not_water.not(); 
 
var landsat = water_landsat.updateMask(water); 
 

 
var RGB = { 
 
    bands: ['B4', 'B3', 'B2'], 
 
    min: -2000, 
 
    max: 2000, 
 
    gamma: [1,1,1], 
 
    }; 
 

 
Map.addLayer(landsat, RGB, 'RGB'); 
 

 
var agriculture = ee.Feature (landsat.clip(agriculture)); 
 
var city = ee.Feature (landsat.clip(city)); 
 
var forest = ee.Feature (landsat.clip(forest)); 
 

 
var polygons = ee.FeatureCollection([agriculture,city,forest]); 
 
    
 
var training = landsat.sampleRegions(
 
    { 
 
    collection: polygons, 
 
    properties: ['agriculture','city', 'forest'], 
 
    scale: 500 
 
    }); 
 

 
var classifier = ee.Classifier.svm(
 
    { 
 
    kernelType: 'RBF', 
 
    gamma: 0.1, 
 
    cost: 10 
 
    }); 
 

 
var trained = classifier.train(training, ('agriculture','city', 'forest'), bands); 
 

 
var classified = landsat.classify(trained); 
 

 
Map.addLayer(classified,{},'classified'); 
 
Map.setCenter(-49.515, -15.824);

Answer 1

Das zweite Argument, die Sie classifier.train() passieren ist der Name der Band mit Klasse-Hotel. Dies sollte eine ganze Zahl sein. Sie fügen den Landsat-Pixeln nie ein Klassenband hinzu, sodass das erste Feature der Feature-Sammlung fehlschlägt (Feature mit der ID 0_0). JavaScript hat keine Tupel wie Python (oder die Sprache, die Sie mehr gewohnt sind), so dass der Code ('agriculture','city', 'forest') zum letzten Element im Parens aufgelöst wird (in diesem Fall forest). Sie sagen GEE also, dass Ihr Klassenband forest ist, und wenn es kein forest Band findet, wird ein Fehler ausgegeben. Es wird klar sein, dass Sie nicht eine Klasse Band hinzufügen, wenn Sie das erste Element des Merkmals Sammlung drucken mit print(training.first());

Was man stattdessen tun sollten, ist eine Band auf die Pixel unter den verschiedenen Polygone hinzugefügt, so etwas wie landType , die einen Wert von 0, 1 oder 2 haben, je nachdem, ob es sich um Landwirtschaft, Stadt oder Wald handelt.