--- a/artifacts/src/main/java/org/dive4elements/river/artifacts/model/WQ.java	Wed Jun 12 10:54:27 2013 +0200
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/model/WQ.java	Wed Jun 12 16:01:46 2013 +0200
@@ -12,6 +12,8 @@
 
 import gnu.trove.TDoubleArrayList;
 
+import java.math.BigDecimal;
+
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -108,5 +110,26 @@
     public void removeNaNs() {
         DoubleUtil.removeNaNs(new TDoubleArrayList [] { ws, qs });
     }
+
+    /** Returns either a modified copy or the same Object with fixed W values.
+     * If a conversion takes place converted is set to true
+     */
+    public static WQ getFixedWQforExportAtGauge(WQ wq, BigDecimal datum) {
+        if (wq.getReferenceSystem() == wq.CENTIMETER_AT_GAUGE) {
+            // Do nothing
+            return wq;
+        }
+        // If we convert we work on a copy to avoid side effects.
+        WQ ret = new WQ(wq.size(), wq.getName());
+
+        // When we convert and have a datum we have a calculated
+        // result at a gauge so we must subtract the datum.
+        double subtractDatum = datum == null ? 0 : datum.doubleValue();
+        for (int i=0; i < wq.size(); i++) {
+            ret.add((wq.get(i)[0] - subtractDatum)* 100, wq.get(i)[1]);
+        }
+        log.debug("Converted W values to centimeter and substracted: " + subtractDatum);
+        return ret;
+    }
 }
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