--- a/gnv-artifacts/ChangeLog	Thu Mar 04 08:03:56 2010 +0000
+++ b/gnv-artifacts/ChangeLog	Thu Mar 04 09:18:53 2010 +0000
@@ -1,3 +1,16 @@
+2010-03-04  Ingo Weinzierl <ingo.weinzierl@intevation.de>
+
+	  Issue171
+
+	* src/main/java/de/intevation/gnv/chart/HorizontalProfileChart.java: Changed
+	  the way to calculate the current distance from startpoint. We do not
+	  calculate the distance between the current point and the last point and
+	  add this value to a variable storing the total distance anymore, but
+	  we take the distance between the current point and the start point. On
+	  this way, we do not need a variable to store the total distance, because
+	  current point - first point == total distance. And there is no
+	  impreciseness in gaps of different layers (see issue171 for this).
+
 2010-03-04  Ingo Weinzierl <ingo.weinzierl@intevation.de>
 
 	* src/main/java/de/intevation/gnv/chart/VerticalProfileChart.java: Added

--- a/gnv-artifacts/src/main/java/de/intevation/gnv/chart/HorizontalProfileChart.java	Thu Mar 04 08:03:56 2010 +0000
+++ b/gnv-artifacts/src/main/java/de/intevation/gnv/chart/HorizontalProfileChart.java	Thu Mar 04 09:18:53 2010 +0000
@@ -27,9 +27,7 @@
     private static Logger log = Logger.getLogger(HorizontalProfileChart.class);
 
     private static WKTReader wktReader = new WKTReader();
-    private        Point     lastPoint;
-    private        double    distance;
-
+    private        Point     firstPoint;
 
     public HorizontalProfileChart(
         ChartLabels labels,
@@ -56,7 +54,6 @@
             shapesVisible
         );
         this.PLOT_ORIENTATION = PlotOrientation.VERTICAL;
-        this.distance         = 0;
     }
 
 
@@ -94,13 +91,18 @@
 
 
     protected void addValue(Result row, Series series) {
+        double distance = 0;
+
         try {
             Point point = (Point) wktReader.read(row.getString("SHAPE"));
-            if (lastPoint != null)
-                distance = distance + DistanceCalculator.calculateDistance(
-                    lastPoint, point
+            if (firstPoint != null) {
+                distance = DistanceCalculator.calculateDistance(
+                    firstPoint, point
                 );
-            lastPoint = point;
+            }
+            else {
+                firstPoint = point;
+            }
 
             ((XYSeries) series).add(
                 distance,
@@ -116,9 +118,8 @@
     protected void addSeries(Series series, String label, int idx) {
         super.addSeries(series, label, idx);
 
-        // reset values used by current series for next series
-        lastPoint = null;
-        distance  = 0;
+        // reset firstPoint for next series
+        firstPoint = null;
     }
 
 
@@ -148,43 +149,48 @@
             results[startPos+1]
         );
 
-        double range        = 0;
-        double distance     = 0;
         int    last         = 0;
         int    current      = 0;
         Point  lastPoint    = null;
         Point  currentPoint = null;
 
+        try {
+            firstPoint = getPoint(results[0]);
+        }
+        catch (ParseException pe) {
+            log.error("Unable to parse start point for gap detection.");
+            return;
+        }
+
         for (int i = startPos+1; i < endPos; i++) {
             try {
                 last         = results[i-1].getInteger(axis);
                 lastPoint    = getPoint(results[i-1]);
                 current      = results[i].getInteger(axis);
                 currentPoint = getPoint(results[i]);
-                distance     = DistanceCalculator.calculateDistance(
-                    lastPoint,
-                    currentPoint
-                );
+                double distance = DistanceCalculator.calculateDistance(
+                    firstPoint,
+                    currentPoint);
+                double distanceOld = DistanceCalculator.calculateDistance(
+                    firstPoint,
+                    lastPoint);
 
                 boolean detected = gridDetection(last, current);
 
                 if (log.isDebugEnabled()) {
-                    log.debug("Current distance from start: " + range);
                     log.debug("Last point: " + lastPoint.toString());
                     log.debug("Current point: " + currentPoint.toString());
-                    log.debug("Distance (current point - last point): " + distance);
+                    log.debug("Current distance from start: " + distance);
                 }
 
                 if (detected) {
                     log.info(
-                        "Gap detected on grid between " + range +
-                        " and " + (range+distance)
-                    );
+                        "Gap detected on grid between " + distanceOld +
+                        " and " + distance);
 
-                    ((XYSeries) series).add(range+0.0001, null);
+                    ((XYSeries) series).add(distance-1d, null);
+                    ((XYSeries) series).add(distanceOld+1d, null);
                 }
-
-                range += distance;
             }
             catch (ParseException pe) {
                 log.warn("Error while parsing point for gap detection.", pe);