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., 675 Mass Ave, Cambridge, MA 02139, USA.

#include <math.h>
#include <simgear/math/point3d.hxx>
#include <simgear/constants.h>
#include <plib/sg.h>
//#include <iomanip.h>

#include "ATCutils.hxx"

// Convert any number to spoken digits
string ConvertNumToSpokenDigits(string n) {
	//cout << "n = " << n << endl;
	string nums[10] = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
	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 a 2 digit rwy number to a spoken-style string
string ConvertRwyNumToSpokenString(int n) {
	string nums[10] = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
	// 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);
}

// 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
	switch(i) {
	case 1 : return("alpha");
	case 2 : return("bravo");
	case 3 : return("charlie");
	case 4 : return("delta");
	case 5 : return("echo");
	case 6 : return("foxtrot");
	case 7 : return("golf");
	case 8 : return("hotel");
	case 9 : return("india");
	case 10 : return("juliet");
	case 11 : return("kilo");
	case 12 : return("lima");
	case 13 : return("mike");
	case 14 : return("november");
	case 15 : return("oscar");
	case 16 : return("papa");
	case 17 : return("quebec");
	case 18 : return("romeo");
	case 19 : return("sierra");
	case 20 : return("tango");
	case 21 : return("uniform");
	case 22 : return("victor");
	case 23 : return("whiskey");
	case 24 : return("x-ray");
	case 25 : return("yankee");
	case 26 : return("zulu");
	}
	// We shouldn't get here
	return("Error");
}

// Given two positions (lat & lon in degrees), get the HORIZONTAL separation (in meters)
double dclGetHorizontalSeparation(Point3D pos1, 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(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 90 in this instance.
double GetHeadingFromTo(Point3D A, 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;
	
	if(xdist >= 0) {
		if(ydist > 0) {
			return(atan(xdist/ydist) * DCL_RADIANS_TO_DEGREES);
		} else if (ydist == 0) {
			return(90.0);
		} else {
			return(180.0 - atan(xdist/fabs(ydist)) * DCL_RADIANS_TO_DEGREES);
		}
	} else {
		if(ydist > 0) {
			return(360.0 - atan(fabs(xdist)/ydist) * DCL_RADIANS_TO_DEGREES);
		} else if (ydist == 0) {
			return(270.0);
		} else {
			return(180.0 + atan(xdist/ydist) * DCL_RADIANS_TO_DEGREES);
		}
	}
}

// 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;
	}
}