Geographic Information Systems Asked on May 29, 2021
My raster file has 29 classes and I applied ‘Reclassify by table’ in QGIS 3.16 to assign 1 to classes 15 and 24 only and all other classes were classified as 0.
I applied the following script to polygonize these two classes which works fine without the reclassify part.
var image = ee.Image("users/parivash89/verceli_tiles_3")
.toInt();
var oldgroup = ee.List([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]);
var newgroup = ee.List([0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,0,0]);
Map.addLayer(newgroup );
Map.centerObject(newgroup );
var classes = newgroup .reduceToVectors({
reducer: ee.Reducer.countEvery(),
scale: 10,
maxPixels: 1e10
});
var result = ee.FeatureCollection(classes);
Map.addLayer(result);
// Export the FeatureCollection to a SHP file.
Export.table.toDrive({
collection: result,
folder: 'GEE_Polygonize',
description:'Vercelli_tiles_3',
fileFormat: 'SHP'
});
But when I add the reclasify part, I get this error:
Cannot add an object of type <List> to the map.
in <global>, line 67
in <global>, line 83
What should I add to choose the selected classes only and polygonize only them?
Remap function was my answer since I was tring to operate on individual values. By adding these lines, the script was done:
.remap([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,0,0]);
Correct answer by Paris on May 29, 2021
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