#pragma once
//
//    FILE: geomath.h
//  AUTHOR: Rob Tillaart
// VERSION: 0.1.1
//    DATE: 2015-07-18
// PURPOSE: Arduino library with geographic math functions
//     URL: https://github.com/RobTillaart/geomath


#include "Arduino.h"


#define GEOMATH_LIB_VERSION        (F("0.1.1"))


//  collection of Math with latitude  / longitude
//  use double for precision 

/*

//  DISTANCE
double haverSine()
double fastHaverSine()
double radius(double lat, double radius);
double equator(double radius);
double angle(double radius, double distance);  //  angle between a person standing right in Iceland and Zambia

*/


double fastHaverSine(double lat1, double long1, double lat2, double  long2)
{
  // assume the sphere has circumference 1 on the equator
  // to keep the number in same order of magnitude
  // helps to keep precision
  double dx = lat2 - lat1;
  double dy = (long2 - long1) * cos(lat2 * (PI / 180.0));
  double dist = sqrt(dx * dx + dy * dy);
  return dist * 111194.93;              // correct for earth sizes ;)
}


double fastHaverSine2(double lat1, double long1, double lat2, double  long2)
{
  // assume the sphere has circumference 1 on the equator
  // to keep the number in same order of magnitude
  // helps to keep precision
  double dx = lat2 - lat1;
  double dy = (long2 - long1) * cos(lat2 * (PI / 180.0));
  return hypot(dx, dy) * 111194.93;              // correct for earth sizes ;)
}


double HaverSine(double lat1, double lon1, double lat2, double lon2)
{
  double ToRad = PI / 180.0;
  double R = 6371000;   //  radius earth in meter

  double dLat = (lat2 - lat1) * ToRad;
  double dLon = (lon2 - lon1) * ToRad;

  double a = sin(dLat / 2) * sin(dLat / 2) +
             cos(lat1 * ToRad) * cos(lat2 * ToRad) *
             sin(dLon / 2) * sin(dLon / 2);

  double c = 2 * atan2(sqrt(a), sqrt(1 - a));

  double d = R * c;
  return d;
}


/////////////////////////////////////////////////
//
//  SPHERE CLASS
//
class sphere
{
public:
  sphere(float radius)
  {
    _radius = radius;
  }
  
  // returns distance in same units as used in constructor.
  float circumference(float latitude)
  {
    return TWO_PI * _radius * cos(latitude * (PI / 180.0));
  }
  
  //  return degrees
  float angle(float distance)
  {
    float a = fmod(distance, _radius * TWO_PI) / _radius;
    return a * (180.0 / PI);
  }
  

private:
  float _radius;
  float _radius_twopi;  // optimization.
};



//  -- END OF FILE --