diff --git a/src/main/java/org/osm2world/core/map_elevation/creation/SimpleEleConstraintEnforcer.java b/src/main/java/org/osm2world/core/map_elevation/creation/SimpleEleConstraintEnforcer.java
index a420eb712..867d93e0f 100644
--- a/src/main/java/org/osm2world/core/map_elevation/creation/SimpleEleConstraintEnforcer.java
+++ b/src/main/java/org/osm2world/core/map_elevation/creation/SimpleEleConstraintEnforcer.java
@@ -4,6 +4,7 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Date;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
@@ -12,6 +13,12 @@
 import java.util.Set;
 
 import org.osm2world.core.map_elevation.data.EleConnector;
+import org.osm2world.core.math.VectorXZ;
+import org.apache.commons.math3.stat.descriptive.rank.Median;
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.Envelope;
+import org.locationtech.jts.index.kdtree.KdNode;
+import org.locationtech.jts.index.kdtree.KdTree;
 
 /**
  * enforcer implementation that ignores many of the constraints,
@@ -34,23 +41,35 @@ public final class SimpleEleConstraintEnforcer implements EleConstraintEnforcer
 
 	@Override
 	public void addConnectors(Iterable<EleConnector> newConnectors) {
-
 		for (EleConnector c : newConnectors) {
 			connectors.add(c);
 		}
-
+		/* build Kd-tree */
+		/* ArrayList<EleConnector> is stored in the KdNode */
+		KdTree kdTree = new KdTree();
+		for (EleConnector c : connectors) {
+			Coordinate co = new Coordinate(c.pos.x, c.pos.z);
+			KdNode node = kdTree.query(co);
+			if (node == null) {
+				ArrayList<EleConnector> cs = new ArrayList<EleConnector>();
+				cs.add(c);
+				kdTree.insert(co, cs);
+			} else {
+				ArrayList<EleConnector> cs = (ArrayList<EleConnector>) node.getData();
+				cs.add(c);
+			}
+		}
 		/* connect connectors */
-
 		for (EleConnector c1 : newConnectors) {
-			for (EleConnector c2 : connectors) {
-
+			Coordinate co = new Coordinate(c1.pos.x, c1.pos.z);
+			KdNode node = kdTree.query(co);
+			ArrayList<EleConnector> cs = (ArrayList<EleConnector>) node.getData();
+			for (EleConnector c2 : cs) {
 				if (c1 != c2 && c1.connectsTo(c2)) {
 					requireSameEle(c1, c2);
 				}
-
 			}
 		}
-
 	}
 
 	@Override