0

I would like to get the union of m (m is variable) different (multi)polygons in Google Earth Engine. The attribute .union() only works with two polygons. See example below for what I have till now.

var ADM2 = ee.FeatureCollection("FAO/GAUL/2015/level2");
var filter1 = ee.Filter.inList('ADM2_NAME', ['Bukidnon']);
var Bukidnon = ADM2.filter(filter1);
var geoBukidnon=Bukidnon.geometry();
Map.centerObject(geoBukidnon)
Map.addLayer(geoBukidnon, {}, 'Bukidnon')

var filter2 = ee.Filter.inList('ADM2_NAME', ['Misamis Oriental']);
var MisamisOriental = ADM2.filter(filter2);
var geoMisamisOriental=MisamisOriental.geometry();
Map.addLayer(geoMisamisOriental, {}, 'Misamis Oriental')

var filter3 = ee.Filter.inList('ADM2_NAME', ['Davao del Norte']);
var DavaodelNorte = ADM2.filter(filter3);
var geoDavaodelNorte=DavaodelNorte.geometry();
Map.addLayer(geoDavaodelNorte, {}, 'Davao del Norte')

// I want the union of geoBukidnon, geoMisamisOriental and geoDavaodelNorte
// but .union() only works with two geometries (see below), whereas I want to get the union 
// of m different (multi)polygons (in this case, m = 3)

var union = geoBukidnon.union(geoMisamisOriental)
Map.addLayer(union, {}, 'union')

var union2 = union.union(geoDavaodelNorte)
Map.addLayer(union2, {}, 'union2')

So I want to get the result of union2 in one step without having to write m-1 lines of code that apply the attribute .union().

1 Answer 1

2

You can merge geometries from all features in your feature collection into one multiPolygon and than use a .dissolve() function.

var filterAll = ee.Filter.inList('ADM2_NAME', 
['Misamis Oriental', 'Davao del Norte', 'Bukidnon']);
var all = ee.FeatureCollection(ADM2.filter(filterAll)).geometry().dissolve()

Link to the code: https://code.earthengine.google.com/d3874a00d59a226671a201d4d7ab713e

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.