--- /dev/null
+/*
+ * 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.gps.geometry;
+
+import static java.lang.Math.PI;
+import static java.lang.Math.cos;
+import static java.lang.Math.sin;
+
+
+/**
+ * Represents the coordinate system for a GPS measurement identified by
+ * <ul>
+ * <li> x1: latitude in degrees </li>
+ * <li> x2: longitude in degrees </li>
+ * <li> x3: elevation in meters </li>
+ * </ul>
+ * This coordinate system models the earth as a sphere of a specific radius.
+ */
+public class SphericalCoordinateSystem implements CoordinateSystem {
+ /**
+ * Earth radius in meters.
+ */
+ private static final double EARTH_RADIUS = 6371000;
+
+
+ /* (non-Javadoc)
+ * @see org.wamblee.gpx.CoordinateSystem#toReferenceSystem(org.wamblee.gpx.Coordinates)
+ */
+ public Coordinates toReferenceSystem(Coordinates aCoordinates) {
+ double latrad = radians(aCoordinates.getX1());
+ double lonrad = radians(aCoordinates.getX2());
+ double coslat = cos(latrad);
+ double sinlat = sin(latrad);
+ double coslon = cos(lonrad);
+ double sinlon = sin(lonrad);
+
+ double trueElevation = EARTH_RADIUS + aCoordinates.getX3();
+ return new Coordinates(trueElevation*coslat*coslon,
+ trueElevation*coslat*sinlon,
+ trueElevation*sinlat);
+
+ }
+
+ private double radians(double aDegrees) {
+ return aDegrees/180.0*PI;
+ }
+}