From a098e38c5ab1d3f9ad94ae12a3a213d13c88aa75 Mon Sep 17 00:00:00 2001
From: DennisOSRM <luxen@kit.edu>
Date: Thu, 15 Dec 2011 17:41:33 +0100
Subject: [PATCH] Util functions to convert between osm (google) x/y and nasa
 grid

---
 Util/ProjectionUtils.h | 55 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 Util/ProjectionUtils.h

diff --git a/Util/ProjectionUtils.h b/Util/ProjectionUtils.h
new file mode 100644
index 000000000..272b1e10f
--- /dev/null
+++ b/Util/ProjectionUtils.h
@@ -0,0 +1,55 @@
+/*
+    open source routing machine
+    Copyright (C) Dennis Luxen, others 2010
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU AFFERO General Public License as published by
+the Free Software Foundation; either version 3 of the License, or
+any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+or see http://www.gnu.org/licenses/agpl.txt.
+ */
+
+#ifndef PROJECTIONUTILS_H_
+#define PROJECTIONUTILS_H_
+
+#include <cmath>
+
+namespace ProjectionUtils {
+
+inline long googleMaxTiles(int zoom) { return( 1L << (17 - zoom) ); }
+
+inline void googleX_to_lng(int zoom, double x, double& lng) {
+    long tilesAtThisZoom =googleMaxTiles(zoom);
+    lng = -180.0 + (x * 360.0 / double(tilesAtThisZoom));
+}
+
+inline void googleY_to_lat(int zoom, double y, double& lat) {
+    // This function is the inverse Mercator projection.
+    // Look up 'Mercator projection' on Wikipedia for details.
+    long   pixels             = googleMaxTiles(zoom) * 256L;
+    double pixelsPerLonRadian = pixels / (2.0 * M_PI);
+    double bitmapOrigo        = pixels / 2;
+
+    double Y = (bitmapOrigo - y*256) / pixelsPerLonRadian;
+
+    double latRad = 2.0 * ::atan( ::exp(Y) ) - M_PI_2;
+    lat = latRad * 180.0 / M_PI;
+}
+
+inline void googleXY_to_latlng( double x, double y, int zoom, double& lng, double& lat ) {
+    googleX_to_lng(zoom,x,lng);
+    googleY_to_lat(zoom,y,lat);
+}
+
+}
+
+#endif /* PROJECTIONUTILS_H_ */