132 lines
4.3 KiB
C++
132 lines
4.3 KiB
C++
/*******************************************************************************
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Module: FGUtility.cpp
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Author: Jon Berndt
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Date started: 01/09/99
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Purpose: Contains utility classes for the FG FDM
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Called by: FGPosition, et. al.
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------------- Copyright (C) 1999 Jon S. Berndt (jsb@hal-pc.org) -------------
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any later
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version.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc., 59 Temple
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Place - Suite 330, Boston, MA 02111-1307, USA.
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Further information about the GNU General Public License can also be found on
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the world wide web at http://www.gnu.org.
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FUNCTIONAL DESCRIPTION
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--------------------------------------------------------------------------------
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This class is a container for all utility classes used by the flight dynamics
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model.
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HISTORY
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--------------------------------------------------------------------------------
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01/09/99 JSB Created
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********************************************************************************
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DEFINES
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*******************************************************************************/
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/*******************************************************************************
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INCLUDES
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*******************************************************************************/
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#ifdef FGFS
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# include <Include/compiler.h>
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# ifdef FG_HAVE_STD_INCLUDES
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# include <cmath>
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# else
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# include <math.h>
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# endif
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#else
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# include <cmath>
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#endif
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#include "FGUtility.h"
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#include "FGState.h"
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#include "FGFDMExec.h"
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/*******************************************************************************
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************************************ CODE **************************************
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*******************************************************************************/
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FGUtility::FGUtility()
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{
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// Move constant stuff to here (if any) so it won't take CPU time
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// in the methods below.
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SeaLevelR = EARTHRAD * ECCENT;
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}
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FGUtility::~FGUtility()
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{
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}
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float FGUtility::ToGeodetic()
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{
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float GeodeticLat, Latitude, Radius, Altitude;
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float tanLat, xAlpha, muAlpha, sinmuAlpha, denom, rhoAlpha, dMu;
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float lPoint, lambdaSL, sinlambdaSL, dLambda, rAlpha;
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Latitude = State->Getlatitude();
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Radius = State->Geth() + EARTHRAD;
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if (( M_PI_2 - Latitude < ONESECOND) ||
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( M_PI_2 + Latitude < ONESECOND)) { // Near a pole
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GeodeticLat = Latitude;
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Altitude = Radius - SeaLevelR;
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} else {
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tanLat = tan(Latitude);
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xAlpha = ECCENT*EARTHRAD /
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sqrt(tanLat*tanLat + ECCENTSQRD);
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muAlpha = atan2(sqrt(EARTHRADSQRD - xAlpha*xAlpha), ECCENT*xAlpha);
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if (Latitude < 0.0) muAlpha = -muAlpha;
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sinmuAlpha = sin(muAlpha);
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dLambda = muAlpha - Latitude;
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rAlpha = xAlpha / cos(Latitude);
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lPoint = Radius - rAlpha;
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Altitude = lPoint*cos(dLambda);
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denom = sqrt(1-EPS*EPS*sinmuAlpha*sinmuAlpha);
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rhoAlpha = EARTHRAD*(1.0 - EPS) / (denom*denom*denom);
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dMu = atan2(lPoint*sin(dLambda),rhoAlpha + Altitude);
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State->SetGeodeticLat(muAlpha - dMu);
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lambdaSL = atan(ECCENTSQRD*tan(GeodeticLat));
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sinlambdaSL = sin(lambdaSL);
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SeaLevelR = sqrt(EARTHRADSQRD / (1 + INVECCENTSQRDM1* sinlambdaSL*sinlambdaSL));
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}
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return 0.0;
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}
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float FGUtility:: FromGeodetic()
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{
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float lambdaSL, sinlambdaSL, coslambdaSL, sinMu, cosMu, py, px;
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float Altitude, SeaLevelR;
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lambdaSL = atan(ECCENTSQRD*tan(State->GetGeodeticLat()));
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sinlambdaSL = sin(lambdaSL);
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coslambdaSL = cos(lambdaSL);
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sinMu = sin(State->GetGeodeticLat());
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cosMu = cos(State->GetGeodeticLat());
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SeaLevelR = sqrt(EARTHRADSQRD /
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(1 + INVECCENTSQRDM1*sinlambdaSL*sinlambdaSL));
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px = SeaLevelR*coslambdaSL + Altitude*cosMu;
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py = SeaLevelR*sinlambdaSL + Altitude*sinMu;
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State->Setlatitude(atan2(py,px));
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return 0.0;
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}
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