Added distance on earth function.

storage/distance.cpp

@@ -0,0 +1,30 @@
+#include "distance.hpp"
+
+#include "../std/algorithm.hpp"
+#include "../std/cmath.hpp"
+
+
+namespace earth
+{
+
+double const PI = atan(1.0) * 4.0;
+
+double Degree2Rad(double deg)
+{
+  return deg / 180.0 * PI;
+}
+
+double DistanceOnSphere(double lat1Deg, double lon1Deg, double lat2Deg, double lon2Deg)
+{
+  double const lat1 = Degree2Rad(lat1Deg);
+  double const lat2 = Degree2Rad(lat2Deg);
+  double const lon1 = Degree2Rad(lon1Deg);
+  double const lon2 = Degree2Rad(lon2Deg);
+
+  double const dlat = sin((lat2 - lat1) / 2.0);
+  double const dlon = sin((lon2 - lon1) / 2.0);
+  double const y = dlat * dlat + dlon * dlon * cos(lat1) * cos(lat2);
+  return 2.0 * atan2(sqrt(y), sqrt(max(0.0, 1.0 - y)));
+}
+
+}

storage/distance.hpp

@@ -0,0 +1,21 @@
+#pragma once
+
+namespace earth
+{
+
+inline double RadiusM() { return 6378000; }
+
+double Degree2Rad(double deg);
+
+/// @name Distance
+/// @param[in] lat1, lat2, lon1, lon2 - in degrees.
+//@{
+double DistanceOnSphere(double lat1Deg, double lon1Deg, double lat2Deg, double lon2Deg);
+
+inline double Distance(double lat1Deg, double lon1Deg, double lat2Deg, double lon2Deg)
+{
+  return RadiusM() * DistanceOnSphere(lat1Deg, lon1Deg, lat2Deg, lon2Deg);
+}
+//@}
+
+}

storage/storage.pro

@@ -6,13 +6,14 @@ CONFIG -= app_bundle
 INCLUDEPATH += ../3rdparty/boost ../3rdparty/googletest/include
 
 HEADERS += \
-  storage.hpp \
   article_info.hpp \
-  storage_common.hpp \
+  distance.hpp \
+  storage.hpp \
 
 SOURCES += \
-  storage.cpp \
   article_info.cpp \
+  distance.cpp \
+  storage.cpp \
 
 # env sources
 SOURCES += \

storage/tests/storage_test.cpp

@@ -1,6 +1,7 @@
 #include <gtest/gtest.h>
 
 #include "storage.hpp"
+#include "distance.hpp"
 
 #include "../env/message_std.hpp"
 #include "../env/logging.hpp"
@@ -188,3 +189,9 @@ TEST(Storage, StorageReadWriteTest)
 
   fs::DeleteFile(name);
 }
+
+TEST(Distance, Smoke)
+{
+  // Equator length from wiki.
+  EXPECT_TRUE(fabs(earth::Distance(0, 0, 0, 180) / 1000.0 - 40075 / 2.0) < 1.0);
+}