--- a/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/tkhstate/BedHeightsFinder.java	Mon Mar 19 14:13:37 2018 +0100
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/tkhstate/BedHeightsFinder.java	Mon Mar 19 16:32:42 2018 +0100
@@ -37,6 +37,12 @@
 
     private final NavigableMap<Double, BedHeightValue> values;
 
+    private double meanBedHeight;
+
+    private double minBedHeight;
+
+    private double maxBedHeight;
+
     /**
      * Create bed height finders from a collection of bed heights.
      */
@@ -139,23 +145,53 @@
     }
 
     public double getMeanBedHeight(final double km) {
+        getBedHeights(km);
+        return this.meanBedHeight;
+    }
 
-        if (this.values.containsKey(km))
-            return this.values.get(km).getHeight();
+    public double getMinBedHeight(final double km) {
+        getBedHeights(km);
+        return this.minBedHeight;
+    }
+
+    public double getMaxBedHeight(final double km) {
+        getBedHeights(km);
+        return this.maxBedHeight;
+    }
+
+    private boolean getBedHeights(final double km) {
+        if (this.values.containsKey(km)) {
+            this.meanBedHeight = (this.values.get(km).getHeight() != null) ? this.values.get(km).getHeight().doubleValue() : Double.NaN;
+            this.minBedHeight = (this.values.get(km).getMinHeight() != null) ? this.values.get(km).getMinHeight().doubleValue() : Double.NaN;
+            this.maxBedHeight = (this.values.get(km).getMaxHeight() != null) ? this.values.get(km).getMaxHeight().doubleValue() : Double.NaN;
+            return true;
+        }
 
         final Entry<Double, BedHeightValue> floorEntry = this.values.floorEntry(km);
         final Entry<Double, BedHeightValue> ceilingEntry = this.values.ceilingEntry(km);
 
-        if (floorEntry == null || ceilingEntry == null)
-            return Double.NaN;
+        if (floorEntry == null || ceilingEntry == null) {
+            this.meanBedHeight = Double.NaN;
+            this.minBedHeight = Double.NaN;
+            this.maxBedHeight = Double.NaN;
+            return false;
+        }
 
-        final double floorKm = floorEntry.getKey();
-        final double floorHeight = floorEntry.getValue().getHeight();
-        final double ceilKm = ceilingEntry.getKey();
-        final double ceilHeight = ceilingEntry.getValue().getHeight();
+        final double floorKm = floorEntry.getKey().doubleValue();
+        final double ceilKm = ceilingEntry.getKey().doubleValue();
 
         // FIXME: check if we always want that...
 
-        return Linear.linear(km, floorKm, ceilKm, floorHeight, ceilHeight);
+        this.meanBedHeight = interpolate(km, floorKm, ceilKm, floorEntry.getValue().getHeight(), ceilingEntry.getValue().getHeight());
+        this.minBedHeight = interpolate(km, floorKm, ceilKm, floorEntry.getValue().getMinHeight(), ceilingEntry.getValue().getMinHeight());
+        this.maxBedHeight = interpolate(km, floorKm, ceilKm, floorEntry.getValue().getMaxHeight(), ceilingEntry.getValue().getMaxHeight());
+        return true;
+    }
+
+    private double interpolate(final double km, final double floorKm, final double ceilKm, final Double floorHeight, final Double ceilHeight) {
+        if ((floorHeight != null) && (ceilHeight != null))
+            return Linear.linear(km, floorKm, ceilKm, floorHeight, ceilHeight);
+        else
+            return Double.NaN;
     }
 }
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