flightgear/src/ATC/ATCutils.cxx

// ATCutils.cxx - Utility functions for the ATC / AI system
//
// Written by David Luff, started March 2002.
//
// Copyright (C) 2002  David C Luff - david.luff@nottingham.ac.uk
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <sstream>

#include <math.h>
#include <simgear/math/point3d.hxx>
#include <simgear/constants.h>
#include <simgear/misc/sg_path.hxx>
#include <simgear/debug/logstream.hxx>
#include <plib/sg.h>
//#include <iomanip.h>

#include <Airports/runways.hxx>
#include <Main/globals.hxx>

#include "ATCutils.hxx"
#include "ATCProjection.hxx"

static const string nums[10] = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "niner"};

// Convert any number to spoken digits
string ConvertNumToSpokenDigits(const string &n) {
	//cout << "n = " << n << endl;
	static const string pt = "decimal";
	string str = "";
	
	for(unsigned int i=0; i<n.length(); ++i) {
		//cout << "n.substr(" << i << ",1 = " << n.substr(i,1) << endl;
		if(n.substr(i,1) == " ") {
			// do nothing
		} else if(n.substr(i,1) == ".") {
			str += pt;
		} else {
			str += nums[atoi((n.substr(i,1)).c_str())];
		}
		if(i != (n.length()-1)) {	// ie. don't add a space at the end.
			str += " ";
		}
	}
	return(str);
}


// Convert an integer to spoken digits
string ConvertNumToSpokenDigits(int n) {
	std::ostringstream buf;
	buf << n;
	return(ConvertNumToSpokenDigits(buf.str()));
}


// Convert a 2 digit rwy number to a spoken-style string
string ConvertRwyNumToSpokenString(int n) {
	// Basic error/sanity checking
	while(n < 0) {
		n += 36;
	}
	while(n > 36) {
		n -= 36;
	}
	if(n == 0) {
		n = 36;	// Is this right?
	}
	
	string str = "";
	int index = n/10;
	str += nums[index];
	n -= (index * 10);
	//str += "-";
	str += " ";		//Changed this for the benefit of the voice token parser - prefer the "-" in the visual output though.
	str += nums[n];
	return(str);
}

// Assumes we get a two-digit string optionally appended with L, R or C
// eg 01 07L 29R 36
// Anything else is not guaranteed to be handled correctly!
string ConvertRwyNumToSpokenString(const string &s) {
	if(s.size() < 3) {
		return(ConvertRwyNumToSpokenString(atoi(s.c_str())));
	} else {
		string r = ConvertRwyNumToSpokenString(atoi(s.substr(0,2).c_str()));
		if(s.substr(2,1) == "L") {
			r += " left";
		} else if(s.substr(2,1) == "R") {
			r += " right";
		} else if(s.substr(2,1) == "C") {
			r += " center";
		} else {
			SG_LOG(SG_ATC, SG_WARN, "WARNING: Unknown suffix " << s.substr(2,1) << " from runway ID " << s << " in ConvertRwyNumToSpokenString(...)");
		}
		return(r);
	}
}
	

// Return the phonetic letter of a letter represented as an integer 1->26
string GetPhoneticIdent(int i) {
	// TODO - Check i is between 1 and 26 and wrap if necessary
	return(GetPhoneticIdent(char('a' + (i-1))));
}

// Return the phonetic letter of a character in the range a-z or A-Z.
// Currently always returns prefixed by lowercase.
string GetPhoneticIdent(char c) {
	c = tolower(c);
	// TODO - Check c is between a and z and wrap if necessary
	switch(c) {
	case 'a' : return("alpha");
	case 'b' : return("bravo");
	case 'c' : return("charlie");
	case 'd' : return("delta");
	case 'e' : return("echo");
	case 'f' : return("foxtrot");
	case 'g' : return("golf");
	case 'h' : return("hotel");
	case 'i' : return("india");
	case 'j' : return("juliet");
	case 'k' : return("kilo");
	case 'l' : return("lima");
	case 'm' : return("mike");
	case 'n' : return("november");
	case 'o' : return("oscar");
	case 'p' : return("papa");
	case 'q' : return("quebec");
	case 'r' : return("romeo");
	case 's' : return("sierra");
	case 't' : return("tango");
	case 'u' : return("uniform");
	case 'v' : return("victor");
	case 'w' : return("whiskey");
	case 'x' : return("x-ray");
	case 'y' : return("yankee");
	case 'z' : return("zulu");
	}
	// We shouldn't get here
	return("Error");
}

// Get the compass direction associated with a heading in degrees
// Currently returns 8 direction resolution (N, NE, E etc...)
// Might be modified in future to return 4, 8 or 16 resolution but defaulting to 8. 
string GetCompassDirection(double h) {
	while(h < 0.0) h += 360.0;
	while(h > 360.0) h -= 360.0;
	if(h < 22.5 || h > 337.5) {
		return("North");
	} else if(h < 67.5) {
		return("North-East");
	} else if(h < 112.5) {
		return("East");
	} else if(h < 157.5) {
		return("South-East");
	} else if(h < 202.5) {
		return("South");
	} else if(h < 247.5) {
		return("South-West");
	} else if(h < 292.5) {
		return("West");
	} else {
		return("North-West");
	}
}

//================================================================================================================

// Given two positions (lat & lon in degrees), get the HORIZONTAL separation (in meters)
double dclGetHorizontalSeparation(const Point3D& pos1, const Point3D& pos2) {
	double x;	//East-West separation
	double y;	//North-South separation
	double z;	//Horizontal separation - z = sqrt(x^2 + y^2)
	
	double lat1 = pos1.lat() * SG_DEGREES_TO_RADIANS;
	double lon1 = pos1.lon() * SG_DEGREES_TO_RADIANS;
	double lat2 = pos2.lat() * SG_DEGREES_TO_RADIANS;
	double lon2 = pos2.lon() * SG_DEGREES_TO_RADIANS;
	
	y = sin(fabs(lat1 - lat2)) * SG_EQUATORIAL_RADIUS_M;
	x = sin(fabs(lon1 - lon2)) * SG_EQUATORIAL_RADIUS_M * (cos((lat1 + lat2) / 2.0));
	z = sqrt(x*x + y*y);
	
	return(z);
}

// Given a point and a line, get the HORIZONTAL shortest distance from the point to a point on the line.
// Expects to be fed orthogonal co-ordinates, NOT lat & lon !
// The units of the separation will be those of the input.
double dclGetLinePointSeparation(double px, double py, double x1, double y1, double x2, double y2) {
	double vecx = x2-x1;
	double vecy = y2-y1;
	double magline = sqrt(vecx*vecx + vecy*vecy);
	double u = ((px-x1)*(x2-x1) + (py-y1)*(y2-y1)) / (magline * magline);
	double x0 = x1 + u*(x2-x1);
	double y0 = y1 + u*(y2-y1);
	vecx = px - x0;
	vecy = py - y0;
	double d = sqrt(vecx*vecx + vecy*vecy);
	if(d < 0) {
		d *= -1;
	}
	return(d);
}

// Given a position (lat/lon/elev), heading and vertical angle (degrees), and distance (meters), calculate the new position.
// This function assumes the world is spherical.  If geodetic accuracy is required use the functions is sg_geodesy instead!
// Assumes that the ground is not hit!!!  Expects heading and angle in degrees, distance in meters. 
Point3D dclUpdatePosition(const Point3D& pos, double heading, double angle, double distance) {
	//cout << setprecision(10) << pos.lon() << ' ' << pos.lat() << '\n';
	heading *= DCL_DEGREES_TO_RADIANS;
	angle *= DCL_DEGREES_TO_RADIANS;
	double lat = pos.lat() * DCL_DEGREES_TO_RADIANS;
	double lon = pos.lon() * DCL_DEGREES_TO_RADIANS;
	double elev = pos.elev();
	//cout << setprecision(10) << lon*DCL_RADIANS_TO_DEGREES << ' ' << lat*DCL_RADIANS_TO_DEGREES << '\n';
	
	double horiz_dist = distance * cos(angle);
	double vert_dist = distance * sin(angle);
	
	double north_dist = horiz_dist * cos(heading);
	double east_dist = horiz_dist * sin(heading);
	
	//cout << distance << ' ' << horiz_dist << ' ' << vert_dist << ' ' << north_dist << ' ' << east_dist << '\n';
	
	double delta_lat = asin(north_dist / (double)SG_EQUATORIAL_RADIUS_M);
	double delta_lon = asin(east_dist / (double)SG_EQUATORIAL_RADIUS_M) * (1.0 / cos(lat));  // I suppose really we should use the average of the original and new lat but we'll assume that this will be good enough.
	//cout << delta_lon*DCL_RADIANS_TO_DEGREES << ' ' << delta_lat*DCL_RADIANS_TO_DEGREES << '\n';
	lat += delta_lat;
	lon += delta_lon;
	elev += vert_dist;
	//cout << setprecision(10) << lon*DCL_RADIANS_TO_DEGREES << ' ' << lat*DCL_RADIANS_TO_DEGREES << '\n';
	
	//cout << setprecision(15) << DCL_DEGREES_TO_RADIANS * DCL_RADIANS_TO_DEGREES << '\n';
	
	return(Point3D(lon*DCL_RADIANS_TO_DEGREES, lat*DCL_RADIANS_TO_DEGREES, elev));
}

// Get a heading in degrees from one lat/lon to another.
// This function assumes the world is spherical.  If geodetic accuracy is required use the functions is sg_geodesy instead!
// Warning - at the moment we are not checking for identical points - currently it returns 0 in this instance.
double GetHeadingFromTo(const Point3D& A, const Point3D& B) {
	double latA = A.lat() * DCL_DEGREES_TO_RADIANS;
	double lonA = A.lon() * DCL_DEGREES_TO_RADIANS;
	double latB = B.lat() * DCL_DEGREES_TO_RADIANS;
	double lonB = B.lon() * DCL_DEGREES_TO_RADIANS;
	double xdist = sin(lonB - lonA) * (double)SG_EQUATORIAL_RADIUS_M * cos((latA+latB)/2.0);
	double ydist = sin(latB - latA) * (double)SG_EQUATORIAL_RADIUS_M;
	double heading = atan2(xdist, ydist) * DCL_RADIANS_TO_DEGREES;
	return heading < 0.0 ? heading + 360 : heading;
}

// Given a heading (in degrees), bound it from 0 -> 360
void dclBoundHeading(double &hdg) {
	while(hdg < 0.0) {
		hdg += 360.0;
	}
	while(hdg > 360.0) {
		hdg -= 360.0;
	}
}

// smallest difference between two angles in degrees
// difference is negative if a1 > a2 and positive if a2 > a1
double GetAngleDiff_deg( const double &a1, const double &a2) {
  
  double a3 = a2 - a1;
  while (a3 < 180.0) a3 += 360.0;
  while (a3 > 180.0) a3 -= 360.0;

  return a3;
}

// Runway stuff
// Given a Point3D (lon/lat/elev) and an FGRunway struct, determine if the point lies on the runway
bool OnRunway(const Point3D& pt, const FGRunway& rwy) {
	FGATCAlignedProjection ortho;
	Point3D centre(rwy._lon, rwy._lat, 0.0);	// We don't need the elev
	ortho.Init(centre, rwy._heading);
	
	Point3D xyc = ortho.ConvertToLocal(centre);
	Point3D xyp = ortho.ConvertToLocal(pt);
	
	//cout << "Length offset = " << fabs(xyp.y() - xyc.y()) << '\n';
	//cout << "Width offset = " << fabs(xyp.x() - xyc.x()) << '\n';
	
	if((fabs(xyp.y() - xyc.y()) < ((rwy._length/2.0) + 5.0)) 
		&& (fabs(xyp.x() - xyc.x()) < (rwy._width/2.0))) {
		return(true);
	}
	
	return(false);
}