From 97f93972c7c3d6e57c12ed7f52575b540bc08990 Mon Sep 17 00:00:00 2001
From: Dennis Luxen <info@project-osrm.org>
Date: Thu, 9 Oct 2014 18:58:58 +0200
Subject: [PATCH] use double precision fp math for mercartor projection and
 point-line projections (for now), fixes #1191

---
 DataStructures/Coordinate.cpp | 26 +++++++++++++-------------
 Util/MercatorUtil.h           |  8 ++++----
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/DataStructures/Coordinate.cpp b/DataStructures/Coordinate.cpp
index c213dc9ef97..e33727c3ed6 100644
--- a/DataStructures/Coordinate.cpp
+++ b/DataStructures/Coordinate.cpp
@@ -258,16 +258,16 @@ float FixedPointCoordinate::ComputePerpendicularDistance(const FixedPointCoordin
     BOOST_ASSERT(query_location.isValid());
 
     // initialize values
-    const float x = lat2y(query_location.lat / COORDINATE_PRECISION);
-    const float y = query_location.lon / COORDINATE_PRECISION;
-    const float a = lat2y(segment_source.lat / COORDINATE_PRECISION);
-    const float b = segment_source.lon / COORDINATE_PRECISION;
-    const float c = lat2y(segment_target.lat / COORDINATE_PRECISION);
-    const float d = segment_target.lon / COORDINATE_PRECISION;
-    float p, q /*,mX*/, nY;
-    if (std::abs(a - c) > std::numeric_limits<float>::epsilon())
+    const double x = lat2y(query_location.lat / COORDINATE_PRECISION);
+    const double y = query_location.lon / COORDINATE_PRECISION;
+    const double a = lat2y(segment_source.lat / COORDINATE_PRECISION);
+    const double b = segment_source.lon / COORDINATE_PRECISION;
+    const double c = lat2y(segment_target.lat / COORDINATE_PRECISION);
+    const double d = segment_target.lon / COORDINATE_PRECISION;
+    double p, q /*,mX*/, nY;
+    if (std::abs(a - c) > std::numeric_limits<double>::epsilon())
     {
-        const float m = (d - b) / (c - a); // slope
+        const double m = (d - b) / (c - a); // slope
         // Projection of (x,y) on line joining (a,b) and (c,d)
         p = ((x + (m * y)) + (m * m * a - m * b)) / (1.f + m * m);
         q = b + m * (p - a);
@@ -293,11 +293,11 @@ float FixedPointCoordinate::ComputePerpendicularDistance(const FixedPointCoordin
     {
         ratio = (segment_target == query_location ? 1.f : 0.f);
     }
-    else if (std::abs(ratio) <= std::numeric_limits<float>::epsilon())
+    else if (std::abs(ratio) <= std::numeric_limits<double>::epsilon())
     {
-        ratio = 0.;
+        ratio = 0.f;
     }
-    else if (std::abs(ratio - 1.f) <= std::numeric_limits<float>::epsilon())
+    else if (std::abs(ratio - 1.f) <= std::numeric_limits<double>::epsilon())
     {
         ratio = 1.f;
     }
@@ -308,7 +308,7 @@ float FixedPointCoordinate::ComputePerpendicularDistance(const FixedPointCoordin
     {
         nearest_location = segment_source;
     }
-    else if (ratio >= 1.)
+    else if (ratio >= 1.f)
     {
         nearest_location = segment_target;
     }
diff --git a/Util/MercatorUtil.h b/Util/MercatorUtil.h
index 31d1139bef3..b4a15b779cc 100644
--- a/Util/MercatorUtil.h
+++ b/Util/MercatorUtil.h
@@ -30,14 +30,14 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <cmath>
 
-inline float y2lat(const float a)
+inline double y2lat(const double a)
 {
-    return 180.f * static_cast<float>(M_1_PI) * (2.f * std::atan(std::exp(a * static_cast<float>(M_PI) / 180.f)) - static_cast<float>(M_PI_2));
+    return 180. * M_1_PI * (2. * std::atan(std::exp(a * M_PI / 180.)) - M_PI_2);
 }
 
-inline float lat2y(const float a)
+inline double lat2y(const double a)
 {
-    return 180.f * static_cast<float>(M_1_PI) * std::log(std::tan(static_cast<float>(M_PI_4) + a * (static_cast<float>(M_PI) / 180.f) / 2.f));
+    return 180. * M_1_PI * std::log(std::tan(M_PI_4 + a * (M_PI / 180.) / 2.));
 }
 
 #endif // MERCATOR_UTIL_H