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[utils] / gps / src / org / wamblee / gpx / ReferenceCoordinateSystem.java

diff --git a/gps/src/org/wamblee/gpx/ReferenceCoordinateSystem.java b/gps/src/org/wamblee/gpx/ReferenceCoordinateSystem.java
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+/*
+ * Copyright 2006 the original author or authors.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.wamblee.gpx;
+
+/**
+ * Reference coordinate system which is the basis for defining metrics.
+ * This is a Cartesian coordinate system.  
+ */
+public class ReferenceCoordinateSystem implements CoordinateSystem {
+
+    /**
+     * Constructs the coordinate system. 
+     *
+     */
+    public ReferenceCoordinateSystem() {
+        // Empty
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see org.wamblee.gpx.CoordinateSystem#toReferenceSystem(org.wamblee.gpx.Coordinates)
+     */
+    public Coordinates toReferenceSystem(Coordinates aCoordinates) {
+        return aCoordinates;
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see org.wamblee.gpx.CoordinateSystem#distance(org.wamblee.gpx.Coordinates,
+     *      org.wamblee.gpx.Coordinates)
+     */
+    private static double distance(Coordinates aC1, Coordinates aC2) {
+        return Math.sqrt(square(aC1.getX1() - aC2.getX1())
+                + square(aC1.getX2() - aC2.getX2())
+                + square(aC1.getX3() - aC2.getX3()));
+    }
+
+    private static double square(double x) {
+        return x * x;
+    }
+    
+    /**
+     * Computes the distance between two points in arbitrary coordinate systems. 
+     * @param aP1 First point. 
+     * @param aP2 Second point. 
+     * @return Distance. 
+     */
+    public static double distance(Point aP1, Point aP2) { 
+        return distance( aP1.getCoordinateSystem().toReferenceSystem(aP1.getCoordinates()), 
+                         aP2.getCoordinateSystem().toReferenceSystem(aP2.getCoordinates()));
+    }
+
+}