Index: /applications/editors/josm/plugins/pdfimport/src/pdfimport/DuplicateNodesFinder.java
===================================================================
--- /applications/editors/josm/plugins/pdfimport/src/pdfimport/DuplicateNodesFinder.java	(revision 24047)
+++ /applications/editors/josm/plugins/pdfimport/src/pdfimport/DuplicateNodesFinder.java	(revision 24047)
@@ -0,0 +1,84 @@
+package pdfimport;
+
+import java.awt.geom.Point2D;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+public class DuplicateNodesFinder {
+
+	/***
+	 * This method finds very close nodes and constructs a mapping from node to suggested representative node.
+	 * Works by performing a sweep and noting down similar nodes.
+	 * @param nodes the nodes to process
+	 * @return map from nodes that need replacement to a representative node.
+	 */
+	public static Map<Point2D, Point2D> findDuplicateNodes(Collection<Point2D> nodes, final double tolerance){
+		List<Point2D> points = new ArrayList<Point2D>(nodes);
+		Collections.sort(points, new Comparator<Point2D>(){
+			public int compare(Point2D o1, Point2D o2) {
+				double diff = o1.getY() - o2.getY();
+				return diff > 0 ? 1 : (diff < 0 ? -1 : 0);
+			}
+		});
+
+		Map<Point2D, Point2D> result = new HashMap<Point2D, Point2D>();
+		TreeMap<Point2D, Point2D> sweepLine = new TreeMap<Point2D, Point2D>(new Comparator<Point2D>(){
+			public int compare(Point2D o1, Point2D o2) {
+				double diff = o1.getX() - o2.getX();
+
+				if (Math.abs(diff) <= tolerance){
+					return 0;
+				}
+
+				return diff > 0 ? 1 : (diff < 0 ? -1 : 0);
+			}
+		});
+
+		double prevY = Double.NEGATIVE_INFINITY;
+
+		for(Point2D point: points) {
+			if (point.getY() - prevY > tolerance){
+				sweepLine.clear();
+				//big offset, clear old points
+			} else {
+				//small offset, test against existing points (there may be more than one)
+				while (sweepLine.containsKey(point)){
+					//a close point found
+					Point2D closePoint = sweepLine.get(point);
+					double dy = point.getY() - closePoint.getY();
+					if (dy <= tolerance){
+						//mark them as close
+						result.put(closePoint, point);
+					}
+
+					sweepLine.remove(closePoint);
+				}
+			}
+
+			prevY = point.getY();
+			sweepLine.put(point, point);
+		}
+
+		//remove cascading relations
+		for(Point2D pt: points) {
+			if (!result.containsKey(pt)){
+				continue;
+			}
+
+			Point2D rep = result.get(pt);
+			while (result.containsKey(rep)){
+				rep = result.get(rep);
+			}
+
+			result.put(pt, rep);
+		}
+
+		return result;
+	}
+}