--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/CrossSectionArtifact.java	Tue Jul 10 13:26:13 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/CrossSectionArtifact.java	Tue Jul 10 15:31:56 2012 +0000
@@ -54,6 +54,12 @@
     /** Name of data item flagging whether we are the newest. */
     public static final String DATA_IS_NEWEST = "cross_section.newest?";
 
+    /** Name of data item storing the previous possible km. */
+    public static final String DATA_PREV_KM = "cross_section.km.previous";
+
+    /** Name of data item storing the next possible km. */
+    public static final String DATA_NEXT_KM = "cross_section.km.next";
+
     /** Own logger. */
     private static final Logger logger =
         Logger.getLogger(CrossSectionArtifact.class);
@@ -98,14 +104,14 @@
             CrossSectionLine csl = csls.get(0);
             // Find min-km of cross sections,
             // then set DATA_KM to min(DATA_KM, minCross).
-            double masterKm = Double.valueOf(getDataAsString(DATA_KM));
-            if (masterKm < csl.getKm().doubleValue()) {
+            double dataKm = Double.valueOf(getDataAsString(DATA_KM));
+            if (dataKm < csl.getKm().doubleValue()) {
                 addStringData(DATA_KM, csl.getKm().toString());
             }
         }
         fs.add(new CrossSectionFacet(0, cs.getDescription()));
 
-        // Find out if we are newest.
+        // Find out if we are newest and become master if so.
         boolean isNewest = CrossSectionFactory.isNewest(cs);
         String newString = (isNewest) ? "1" : "0";
         addStringData(DATA_IS_NEWEST, newString);
@@ -136,6 +142,15 @@
     }
 
 
+    public Double getNextKm() {
+        return getDataAsDouble(DATA_NEXT_KM);
+    }
+
+    public Double getPrevKm() {
+        return getDataAsDouble(DATA_PREV_KM);
+    }
+
+
     /**
      * Create and return a new StaticState with charting output.
      */
@@ -238,6 +253,9 @@
      * Get CrossSectionLine spatially closest to what is specified in the data
      * "cross_section.km", null if considered too far.
      *
+     * It also adds DataItems to store the next and previous (numerically)
+     * values at which cross-section data was recorded.
+     *
      * @return CrossSectionLine closest to "cross_section.km", might be null
      *         if considered too far.
      */
@@ -258,6 +276,9 @@
         Double floor = kms.floorKey(wishKM);
         Double ceil  = kms.ceilingKey(wishKM);
 
+        Double nextKm;
+        Double prevKm;
+
         double floorD = floor != null
             ? Math.abs(floor - wishKM)
             : Double.MAX_VALUE;
@@ -266,13 +287,33 @@
             ? Math.abs(ceil - wishKM)
             : Double.MAX_VALUE;
 
-        double km = floorD < ceilD ? floor : ceil;
+        double km;
+        if (floorD < ceilD) {
+            km = floor;
+        }
+        else {
+            km = ceil;
+        }
 
         // If we are too far from the wished km, return null.
         if (Math.abs(km - wishKM) > TOO_FAR) {
             return null;
         }
 
+        // Store next and previous km.
+        nextKm = kms.higherKey(km);
+        prevKm = kms.lowerKey(km);
+
+        if (prevKm == null) {
+            prevKm = -1d;
+        }
+        if (nextKm == null) {
+            nextKm = -1d;
+        }
+
+        addStringData(DATA_PREV_KM, prevKm.toString());
+        addStringData(DATA_NEXT_KM, nextKm.toString());
+
         return FastCrossSectionLineFactory
             .getCrossSectionLine(crossSection, km);
     }