//LatLong- UTM conversion.cpp
//Lat Long - UTM, UTM - Lat Long conversions

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "constants.h"
#include "LatLong-UTMconversion.h"


/*Reference ellipsoids derived from Peter H. Dana's website- 
http://www.utexas.edu/depts/grg/gcraft/notes/datum/elist.html
Department of Geography, University of Texas at Austin
Internet: pdana@mail.utexas.edu
3/22/95

Source
Defense Mapping Agency. 1987b. DMA Technical Report: Supplement to Department of Defense World Geodetic System
1984 Technical Report. Part I and II. Washington, DC: Defense Mapping Agency
*/



void LLtoUTM(int ReferenceEllipsoid,const double Lat,const double Long, 
			 double &UTMNorthing, double &UTMEasting, char* UTMZone)
{
//converts lat/long to UTM coords.  Equations from USGS Bulletin 1532 
//East Longitudes are positive, West longitudes are negative. 
//North latitudes are positive, South latitudes are negative
//Lat and Long are in decimal degrees
	//Written by Chuck Gantz- chuck.gantz@globalstar.com

	double a = ellipsoid[ReferenceEllipsoid].EquatorialRadius;
	double eccSquared = ellipsoid[ReferenceEllipsoid].eccentricitySquared;
	double k0 = 0.9996;

	double LongOrigin;
	double eccPrimeSquared;
	double N, T, C, A, M;
	
//Make sure the longitude is between -180.00 .. 179.9
	double LongTemp = (Long+180)-int((Long+180)/360)*360-180; // -180.00 .. 179.9;

	double LatRad = Lat*deg2rad;
	double LongRad = LongTemp*deg2rad;
	double LongOriginRad;
	int    ZoneNumber;

	ZoneNumber = int((LongTemp + 180)/6) + 1;
  
	if( Lat >= 56.0 && Lat < 64.0 && LongTemp >= 3.0 && LongTemp < 12.0 )
		ZoneNumber = 32;

  // Special zones for Svalbard
/*	if( Lat >= 72.0 && Lat < 84.0 ) 
	{
	  if(      LongTemp >= 0.0  && LongTemp <  9.0 ) ZoneNumber = 31;
	  else if( LongTemp >= 9.0  && LongTemp < 21.0 ) ZoneNumber = 33;
	  else if( LongTemp >= 21.0 && LongTemp < 33.0 ) ZoneNumber = 35;
	  else if( LongTemp >= 33.0 && LongTemp < 42.0 ) ZoneNumber = 37;
	 }
*/
	LongOrigin = (ZoneNumber - 1)*6 - 180 + 3;  //+3 puts origin in middle of zone
	LongOriginRad = LongOrigin * deg2rad;

	//compute the UTM Zone from the latitude and longitude
	sprintf(UTMZone, "%d%c", ZoneNumber, UTMLetterDesignator(Lat));

	eccPrimeSquared = (eccSquared)/(1-eccSquared);

	N = a/sqrt(1-eccSquared*sin(LatRad)*sin(LatRad));
	T = tan(LatRad)*tan(LatRad);
	C = eccPrimeSquared*cos(LatRad)*cos(LatRad);
	A = cos(LatRad)*(LongRad-LongOriginRad);

	M = a*((1	- eccSquared/4		- 3*eccSquared*eccSquared/64	- 5*eccSquared*eccSquared*eccSquared/256)*LatRad 
				- (3*eccSquared/8	+ 3*eccSquared*eccSquared/32	+ 45*eccSquared*eccSquared*eccSquared/1024)*sin(2*LatRad)
									+ (15*eccSquared*eccSquared/256 + 45*eccSquared*eccSquared*eccSquared/1024)*sin(4*LatRad) 
									- (35*eccSquared*eccSquared*eccSquared/3072)*sin(6*LatRad));
	
	UTMEasting = (double)(k0*N*(A+(1-T+C)*A*A*A/6
					+ (5-18*T+T*T+72*C-58*eccPrimeSquared)*A*A*A*A*A/120)
					+ 500000.0);

	UTMNorthing = (double)(k0*(M+N*tan(LatRad)*(A*A/2+(5-T+9*C+4*C*C)*A*A*A*A/24
				 + (61-58*T+T*T+600*C-330*eccPrimeSquared)*A*A*A*A*A*A/720)));
	if(Lat < 0)
		UTMNorthing += 10000000.0; //10000000 meter offset for southern hemisphere
}

char UTMLetterDesignator(double Lat)
{
//This routine determines the correct UTM letter designator for the given latitude
//returns 'Z' if latitude is outside the UTM limits of 84N to 80S
	//Written by Chuck Gantz- chuck.gantz@globalstar.com
	char LetterDesignator;

	if((84 >= Lat) && (Lat >= 72)) LetterDesignator = 'X';
	else if((72 > Lat) && (Lat >= 64)) LetterDesignator = 'W';
	else if((64 > Lat) && (Lat >= 56)) LetterDesignator = 'V';
	else if((56 > Lat) && (Lat >= 48)) LetterDesignator = 'U';
	else if((48 > Lat) && (Lat >= 40)) LetterDesignator = 'T';
	else if((40 > Lat) && (Lat >= 32)) LetterDesignator = 'S';
	else if((32 > Lat) && (Lat >= 24)) LetterDesignator = 'R';
	else if((24 > Lat) && (Lat >= 16)) LetterDesignator = 'Q';
	else if((16 > Lat) && (Lat >= 8)) LetterDesignator = 'P';
	else if(( 8 > Lat) && (Lat >= 0)) LetterDesignator = 'N';
	else if(( 0 > Lat) && (Lat >= -8)) LetterDesignator = 'M';
	else if((-8> Lat) && (Lat >= -16)) LetterDesignator = 'L';
	else if((-16 > Lat) && (Lat >= -24)) LetterDesignator = 'K';
	else if((-24 > Lat) && (Lat >= -32)) LetterDesignator = 'J';
	else if((-32 > Lat) && (Lat >= -40)) LetterDesignator = 'H';
	else if((-40 > Lat) && (Lat >= -48)) LetterDesignator = 'G';
	else if((-48 > Lat) && (Lat >= -56)) LetterDesignator = 'F';
	else if((-56 > Lat) && (Lat >= -64)) LetterDesignator = 'E';
	else if((-64 > Lat) && (Lat >= -72)) LetterDesignator = 'D';
	else if((-72 > Lat) && (Lat >= -80)) LetterDesignator = 'C';
	else LetterDesignator = 'Z'; //This is here as an error flag to show that the Latitude is outside the UTM limits

	return LetterDesignator;
}


void UTMtoLL(int ReferenceEllipsoid, const double UTMNorthing, const double UTMEasting, const char* UTMZone,
			  double& Lat,  double& Long )
{
//converts UTM coords to lat/long.  Equations from USGS Bulletin 1532 
//East Longitudes are positive, West longitudes are negative. 
//North latitudes are positive, South latitudes are negative
//Lat and Long are in decimal degrees. 
	//Written by Chuck Gantz- chuck.gantz@globalstar.com

	double k0 = 0.9996;
	double a = ellipsoid[ReferenceEllipsoid].EquatorialRadius;
	double eccSquared = ellipsoid[ReferenceEllipsoid].eccentricitySquared;
	double eccPrimeSquared;
	double e1 = (1-sqrt(1-eccSquared))/(1+sqrt(1-eccSquared));
	double N1, T1, C1, R1, D, M;
	double LongOrigin;
	double mu, phi1, phi1Rad;
	double x, y;
	int ZoneNumber;
	char* ZoneLetter;
	int NorthernHemisphere; //1 for northern hemispher, 0 for southern

	x = UTMEasting - 500000.0; //remove 500,000 meter offset for longitude
	y = UTMNorthing;

	ZoneNumber = strtoul(UTMZone, &ZoneLetter, 10);
	if((*ZoneLetter - 'N') >= 0)
		NorthernHemisphere = 1;//point is in northern hemisphere
	else
	{
		NorthernHemisphere = 0;//point is in southern hemisphere
		y -= 10000000.0;//remove 10,000,000 meter offset used for southern hemisphere
	}

	LongOrigin = (ZoneNumber - 1)*6 - 180 + 3;  //+3 puts origin in middle of zone

	eccPrimeSquared = (eccSquared)/(1-eccSquared);

	M = y / k0;
	mu = M/(a*(1-eccSquared/4-3*eccSquared*eccSquared/64-5*eccSquared*eccSquared*eccSquared/256));

	phi1Rad = mu	+ (3*e1/2-27*e1*e1*e1/32)*sin(2*mu) 
				+ (21*e1*e1/16-55*e1*e1*e1*e1/32)*sin(4*mu)
				+(151*e1*e1*e1/96)*sin(6*mu);
	phi1 = phi1Rad*rad2deg;

	N1 = a/sqrt(1-eccSquared*sin(phi1Rad)*sin(phi1Rad));
	T1 = tan(phi1Rad)*tan(phi1Rad);
	C1 = eccPrimeSquared*cos(phi1Rad)*cos(phi1Rad);
	R1 = a*(1-eccSquared)/pow(1-eccSquared*sin(phi1Rad)*sin(phi1Rad), 1.5);
	D = x/(N1*k0);

	Lat = phi1Rad - (N1*tan(phi1Rad)/R1)*(D*D/2-(5+3*T1+10*C1-4*C1*C1-9*eccPrimeSquared)*D*D*D*D/24
					+(61+90*T1+298*C1+45*T1*T1-252*eccPrimeSquared-3*C1*C1)*D*D*D*D*D*D/720);
	Lat = Lat * rad2deg;

	Long = (D-(1+2*T1+C1)*D*D*D/6+(5-2*C1+28*T1-3*C1*C1+8*eccPrimeSquared+24*T1*T1)
					*D*D*D*D*D/120)/cos(phi1Rad);
	Long = LongOrigin + Long * rad2deg;

}
