GPS Receivers, Geodesy, and Geocaching: Vincenty’s Formula

/* Gavaghan.Geodesy by Mike Gavaghan
 * 
 * http://www.gavaghan.org/blog/free-source-code/geodesy-library-vincentys-formula/
 * 
 * This code may be freely used and modified on any personal or professional
 * project.  It comes with no warranty.
 */
using System;
using System.Text;

namespace Gavaghan.Geodesy
{
  /// <summary>
  /// This is the outcome of a three dimensional geodetic calculation.  It represents
  /// the path a between two GlobalPositions for a specified reference ellipsoid.
  /// </summary>
  [Serializable]
  public struct GeodeticMeasurement
  {
    /// <summary>The average geodetic curve.</summary>
    private readonly GeodeticCurve mCurve;

    /// <summary>The elevation change, in meters, going from the starting to the ending point.</summary>
    private readonly double mElevationChange;

    /// <summary>The distance travelled, in meters, going from one point to the next.</summary>
    private readonly double mP2P;

    /// <summary>
    /// Creates a new instance of GeodeticMeasurement.
    /// </summary>
    /// <param name="averageCurve">the geodetic curve as measured at the average elevation between two points</param>
    /// <param name="elevationChange">the change in elevation, in meters, going from the starting point to the ending point</param>
    public GeodeticMeasurement(GeodeticCurve averageCurve, double elevationChange)
    {
      double ellDist = averageCurve.EllipsoidalDistance;

      mCurve = averageCurve;
      mElevationChange = elevationChange;
      mP2P = Math.Sqrt(ellDist * ellDist + mElevationChange * mElevationChange);
    }

    /// <summary>
    /// Get the average geodetic curve.  This is the geodetic curve as measured
    /// at the average elevation between two points.
    /// </summary>
    public GeodeticCurve AverageCurve
    {
      get { return mCurve; }
    }

    /// <summary>
    /// Get the ellipsoidal distance (in meters).  This is the length of the average geodetic
    /// curve.  For actual point-to-point distance, use PointToPointDistance property.
    /// </summary>
    public double EllipsoidalDistance
    {
      get { return mCurve.EllipsoidalDistance; }
    }

    /// <summary>
    /// Get the azimuth.  This is angle from north from start to end.
    /// </summary>
    public Angle Azimuth
    {
      get { return mCurve.Azimuth; }
    }

    /// <summary>
    /// Get the reverse azimuth.  This is angle from north from end to start.
    /// </summary>
    public Angle ReverseAzimuth
    {
      get { return mCurve.ReverseAzimuth; }
    }

    /// <summary>
    /// Get the elevation change, in meters, going from the starting to the ending point.
    /// </summary>
    public double ElevationChange
    {
      get { return mElevationChange; }
    }

    /// <summary>
    /// Get the distance travelled, in meters, going from one point to the next.
    /// </summary>
    public double PointToPointDistance
    {
      get { return mP2P; }
    }

    /// <summary>
    /// Get the GeodeticMeasurement as a string
    /// </summary>
    /// <returns></returns>
    public override string ToString()
    {
      StringBuilder builder = new StringBuilder();

      builder.Append(mCurve.ToString());
      builder.Append(";elev12=");
      builder.Append(mElevationChange);
      builder.Append(";p2p=");
      builder.Append(mP2P);

      return builder.ToString();
    }
  }
}