Add function that returns the compass points.

We support 16-wind compass rose.
vahancho · Feb 16, 2024 · 0e7ac11 · 0e7ac11
1 parent d7916dc
commit 0e7ac11
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diff --git a/include/coordinate.h b/include/coordinate.h
@@ -44,6 +44,13 @@ class ERKIR_EXPORT Coordinate
     DD   ///< Decimal Degrees (D.D°)
   };
 
+  enum class CompassPrecision
+  {
+    Cardinal,
+    Intercardinal,
+    SecondaryIntercardinal
+  };
+
   //! Constructs a coordinate by the given decimal degrees.
   Coordinate(double degrees);
 
@@ -67,6 +74,19 @@ class ERKIR_EXPORT Coordinate
   /// Constrain degrees to range 0..360.0 (e.g. for bearings); -1 => 359, 361 => 1.
   static double wrap360(double degrees);
 
+  /// Returns compass point (to given precision) for supplied bearing.
+  /*!
+    @param   bearing   Bearing in degrees from north.
+    @param   precision Precision (Cardinal, Intercardinal, SecondaryIntercardinal).
+    @returns Compass point for supplied bearing.
+
+    @example
+       const point = Coordinate::compassPoint(24);    // point = 'NNE'
+       const point = Coordinate::compassPoint(24, 1); // point = 'N'
+  */
+  static std::string compassPoint(double bearing,
+                                  CompassPrecision precision = CompassPrecision::SecondaryIntercardinal);
+
 protected:
   std::string toBaseString(Format format, int precision) const;
 

diff --git a/src/coordinate.cpp b/src/coordinate.cpp
@@ -256,6 +256,23 @@ std::string Coordinate::toBaseString(Format format, int precision) const
   return ss.str();
 }
 
+std::string Coordinate::compassPoint(double bearing, CompassPrecision precision)
+{
+  const auto wrappedBearing = wrap360(bearing); // normalize to range 0..360°
+
+  static constexpr const char *cardinals[] = {
+    "N", "NNE", "NE", "ENE",
+    "E", "ESE", "SE", "SSE",
+    "S", "SSW", "SW", "WSW",
+    "W", "WNW", "NW", "NNW"
+  };
+  static constexpr const int ns[] = { 4, 8, 16 };
+
+  const auto p = static_cast<int>(precision);
+  const auto n = ns[p];
+  return cardinals[(int)(std::round(wrappedBearing * n / 360.0)) % n * 16 / n];
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 Latitude::Latitude(double degree)

diff --git a/test/test.cpp b/test/test.cpp
@@ -491,6 +491,28 @@ int main()
     }
   }
 
+  // Compass Points
+  {
+    verifyString(  "N", Coordinate::compassPoint(1));
+    verifyString(  "N", Coordinate::compassPoint(720));
+    verifyString(  "N", Coordinate::compassPoint(0));
+    verifyString(  "N", Coordinate::compassPoint(-1));
+    verifyString(  "N", Coordinate::compassPoint(359));
+    verifyString(  "S", Coordinate::compassPoint(180));
+    verifyString("NNE", Coordinate::compassPoint(24));
+    verifyString(  "N", Coordinate::compassPoint(24, Coordinate::CompassPrecision::Cardinal));
+    verifyString( "NE", Coordinate::compassPoint(24, Coordinate::CompassPrecision::Intercardinal));
+    verifyString("NNE", Coordinate::compassPoint(24, Coordinate::CompassPrecision::SecondaryIntercardinal));
+    verifyString( "SW", Coordinate::compassPoint(226));
+    verifyString(  "W", Coordinate::compassPoint(226, Coordinate::CompassPrecision::Cardinal));
+    verifyString( "SW", Coordinate::compassPoint(226, Coordinate::CompassPrecision::Intercardinal));
+    verifyString( "SW", Coordinate::compassPoint(226, Coordinate::CompassPrecision::SecondaryIntercardinal));
+    verifyString("WSW", Coordinate::compassPoint(237));
+    verifyString(  "W", Coordinate::compassPoint(237, Coordinate::CompassPrecision::Cardinal));
+    verifyString( "SW", Coordinate::compassPoint(237, Coordinate::CompassPrecision::Intercardinal));
+    verifyString("WSW", Coordinate::compassPoint(237, Coordinate::CompassPrecision::SecondaryIntercardinal));
+  }
+
   //////////////////////////////////////////////////////////////////////////////
 
   // Ellipsoidal points