Optimization for Gnomonic and GonmonicData

Author: oldrev

GeographicLib/GeodesicData.cs

@@ -25,62 +25,62 @@ public sealed class GeodesicData
         /// <summary>
         /// latitude of point 1 (degrees).
         /// </summary>
-        public double lat1;
+        public double lat1 { get; set; }
 
         /// <summary>
         /// longitude of point 1 (degrees).
         /// </summary>
-        public double lon1;
+        public double lon1 { get; set; }
 
         /// <summary>
         /// azimuth at point 1 (degrees).
         /// </summary>
-        public double azi1;
+        public double azi1 { get; set; }
 
         /// <summary>
         /// latitude of point 2 (degrees).
         /// </summary>
-        public double lat2;
+        public double lat2 { get; set; }
 
         /// <summary>
         /// longitude of point 2 (degrees).
         /// </summary>
-        public double lon2;
+        public double lon2 { get; set; }
 
         /// <summary>
         /// azimuth at point 2 (degrees).
         /// </summary>
-        public double azi2;
+        public double azi2 { get; set; }
 
         /// <summary>
         /// distance between point 1 and point 2 (meters).
         /// </summary>
-        public double s12;
+        public double s12 { get; set; }
 
         /// <summary>
         /// arc length on the auxiliary sphere between point 1 and point 2 (degrees).
         /// </summary>
-        public double a12;
+        public double a12 { get; set; }
 
         /// <summary>
         /// reduced length of geodesic (meters).
         /// </summary>
-        public double m12;
+        public double m12 { get; set; }
 
         /// <summary>
         /// geodesic scale of point 2 relative to point 1 (dimensionless).
         /// </summary>
-        public double M12;
+        public double M12 { get; set; }
 
         /// <summary>
         /// geodesic scale of point 1 relative to point 2 (dimensionless).
         /// </summary>
-        public double M21;
+        public double M21 { get; set; }
 
         /// <summary>
         /// Area under the geodesic (meters<sup>2</sup>).
         /// </summary>
-        public double S12;
+        public double S12 { get; set; }
 
         /// <summary>
         /// Initialize all the fields to Double.NaN.

GeographicLib/Gnomonic.cs

@@ -13,8 +13,7 @@
 namespace GeographicLib
 {
 
-    /**
-     * Gnomonic projection.
+    /*
      * <p>
      * <i>Note: Gnomonic.java has been ported to Java from its C++ equivalent
      * Gnomonic.cpp, authored by C. F. F. Karney and licensed under MIT/X11
@@ -136,25 +135,24 @@ namespace GeographicLib
      * </pre>
      */
 
+    /// <summary>
+    /// Gnomonic projection.
+    /// </summary>
     public readonly struct Gnomonic
     {
         private static readonly double eps_ = 0.01 * Math.Sqrt(GeoMath.Epsilon);
         private const int numit_ = 10;
 
-        private readonly Geodesic _earth;
-        private readonly double _a, _f;
+        public Geodesic Earth { get; }
 
-        /**
-         * Constructor for Gnomonic.
-         * <p>
-         * @param earth the {@link Geodesic} object to use for geodesic
-         *   calculations.
-         */
+        /// <summary>
+        /// Constructor for Gnomonic.
+        /// </summary>
+        /// <param name="earth">earth the <see cref="GeographicLib.Geodesic"/> object to use for geodesic calculations
+        /// </param>
         public Gnomonic(Geodesic earth)
         {
-            _earth = earth;
-            _a = _earth.MajorRadius;
-            _f = _earth.Flattening;
+            this.Earth = earth;
         }
 
         /**
@@ -181,23 +179,22 @@ public Gnomonic(Geodesic earth)
          */
         public GnomonicData Forward(double lat0, double lon0, double lat, double lon)
         {
-            GeodesicData inv =
-              _earth.Inverse(lat0, lon0, lat, lon,
-                             GeodesicMask.AZIMUTH | GeodesicMask.GEODESICSCALE |
-                             GeodesicMask.REDUCEDLENGTH);
-            GnomonicData fwd =
-              new GnomonicData(lat0, lon0, lat, lon, Double.NaN, Double.NaN,
-                               inv.azi2, inv.M12);
+            GeodesicData inv = Earth.Inverse(
+                lat0, lon0, lat, lon,
+                GeodesicMask.AZIMUTH | GeodesicMask.GEODESICSCALE | GeodesicMask.REDUCEDLENGTH);
 
             if (inv.M12 > 0)
             {
-                double rho = inv.m12 / inv.M12;
-                Pair p = GeoMath.Sincosd(inv.azi1);
-                fwd.x = rho * p.First;
-                fwd.y = rho * p.Second;
+                var rho = inv.m12 / inv.M12;
+                var p = GeoMath.Sincosd(inv.azi1);
+                var x = rho * p.First;
+                var y = rho * p.Second;
+                return new GnomonicData(lat0, lon0, lat, lon, x, y, inv.azi2, inv.M12);
+            }
+            else
+            {
+                return new GnomonicData(lat0, lon0, lat, lon, Double.NaN, Double.NaN, inv.azi2, inv.M12);
             }
-
-            return fwd;
         }
 
         /**
@@ -226,20 +223,19 @@ public GnomonicData Forward(double lat0, double lon0, double lat, double lon)
          */
         public GnomonicData Reverse(double lat0, double lon0, double x, double y)
         {
-            GnomonicData rev =
-              new GnomonicData(lat0, lon0, Double.NaN, Double.NaN, x, y, Double.NaN,
-                               Double.NaN);
 
-            double azi0 = GeoMath.Atan2d(x, y);
-            double rho = GeoMath.Hypot(x, y);
-            double s = _a * Math.Atan(rho / _a);
-            bool little = rho <= _a;
+            var azi0 = GeoMath.Atan2d(x, y);
+            var rho = GeoMath.Hypot(x, y);
+            var s = this.MajorRadius * Math.Atan(rho / this.MajorRadius);
+            var little = rho <= this.MajorRadius;
 
             if (!little)
+            {
                 rho = 1 / rho;
+            }
 
-            GeodesicLine line =
-              _earth.Line(lat0, lon0, azi0, GeodesicMask.LATITUDE
+            var line =
+              Earth.Line(lat0, lon0, azi0, GeodesicMask.LATITUDE
                           | GeodesicMask.LONGITUDE | GeodesicMask.AZIMUTH
                           | GeodesicMask.DISTANCE_IN | GeodesicMask.REDUCEDLENGTH
                           | GeodesicMask.GEODESICSCALE);
@@ -249,46 +245,48 @@ public GnomonicData Reverse(double lat0, double lon0, double x, double y)
 
             while (count-- > 0)
             {
-                pos =
-                  line.Position(s, GeodesicMask.LONGITUDE | GeodesicMask.LATITUDE
+                pos = line.Position(s, 
+                                  GeodesicMask.LONGITUDE | GeodesicMask.LATITUDE
                                 | GeodesicMask.AZIMUTH | GeodesicMask.DISTANCE_IN
                                 | GeodesicMask.REDUCEDLENGTH
                                 | GeodesicMask.GEODESICSCALE);
 
                 if (trip > 0)
+                {
                     break;
+                }
 
-                double ds =
-                  little ? ((pos.m12 / pos.M12) - rho) * pos.M12 * pos.M12
-                  : (rho - (pos.M12 / pos.m12)) * pos.m12 * pos.m12;
+                double ds = little ? ((pos.m12 / pos.M12) - rho) * pos.M12 * pos.M12 
+                    : (rho - (pos.M12 / pos.m12)) * pos.m12 * pos.m12;
                 s -= ds;
 
-                if (Math.Abs(ds) <= eps_ * _a)
+                if (Math.Abs(ds) <= eps_ * this.MajorRadius)
+                {
                     trip++;
+                }
             }
 
             if (trip == 0)
-                return rev;
-
-            rev.lat = pos.lat2;
-            rev.lon = pos.lon2;
-            rev.azi = pos.azi2;
-            rev.rk = pos.M12;
-
-            return rev;
+            {
+                return new GnomonicData(lat0, lon0, Double.NaN, Double.NaN, x, y, Double.NaN, Double.NaN);
+            }
+            else
+            {
+                return new GnomonicData(lat0, lon0, pos.lat2, pos.lon2, x, y, pos.azi2, pos.M12);
+            }
         }
 
         /**
          * @return <i>a</i> the equatorial radius of the ellipsoid (meters).  This is
          *   the value inherited from the Geodesic object used in the constructor.
          **********************************************************************/
-        public double MajorRadius => _a;
+        public double MajorRadius => this.Earth.MajorRadius;
 
         /**
          * @return <i>f</i> the  flattening of the ellipsoid.  This is
          *   the value inherited from the Geodesic object used in the constructor.
          **********************************************************************/
-        public double Flattening => _f;
+        public double Flattening => this.Earth.Flattening;
     }
 
 }

GeographicLib/GnomonicData.cs

@@ -23,48 +23,40 @@ namespace GeographicLib
      * and it always includes the fields <i>x</i>, <i>y</i>, <i>azi</i>. and
      * <i>rk</i>.
      **********************************************************************/
-    public sealed class GnomonicData
+    public readonly struct GnomonicData
     {
         /**
          * latitude of center point of projection (degrees).
          **********************************************************************/
-        public double lat0 { get; set; }
+        public double lat0 { get; }
         /**
          * longitude of center point of projection (degrees).
          **********************************************************************/
-        public double lon0 { get; set; }
+        public double lon0 { get; }
         /**
          * latitude of point (degrees).
          **********************************************************************/
-        public double lat { get; set; }
+        public double lat { get; }
         /**
          * longitude of point (degrees).
          **********************************************************************/
-        public double lon { get; set; }
+        public double lon { get; }
         /**
          * easting of point (meters).
          **********************************************************************/
-        public double x { get; set; }
+        public double x { get; }
         /**
          * northing of point (meters).
          **********************************************************************/
-        public double y { get; set; }
+        public double y { get; }
         /**
          * azimuth of geodesic at point (degrees).
          **********************************************************************/
-        public double azi { get; set; }
+        public double azi { get; }
         /**
          * reciprocal of azimuthal scale at point.
          **********************************************************************/
-        public double rk { get; set; }
-
-        /**
-         * Initialize all the fields to Double.NaN.
-         **********************************************************************/
-        public GnomonicData()
-        {
-            lat0 = lon0 = lat = lon = x = y = azi = rk = Double.NaN;
-        }
+        public double rk { get; }
 
         /**
          * Constructor initializing all the fields for gnomonic projection of a point
@@ -88,8 +80,8 @@ public GnomonicData()
          * @param rk
          *          reciprocal of azimuthal scale at point.
          */
-        public GnomonicData(double lat0, double lon0, double lat, double lon,
-            double x, double y, double azi, double rk)
+        public GnomonicData(double lat0 = double.NaN, double lon0 = double.NaN, double lat = double.NaN, double lon = double.NaN,
+            double x = double.NaN, double y = double.NaN, double azi = double.NaN, double rk = double.NaN)
         {
             this.lat0 = lat0;
             this.lon0 = lon0;