146 lines
3.6 KiB
C
146 lines
3.6 KiB
C
// constants.h -- various constant definitions
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//
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// Written by Curtis Olson, started February 2000.
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//
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// Copyright (C) 2000 Curtis L. Olson - curt@flightgear.org
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Library General Public License for more details.
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//
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// You should have received a copy of the GNU Library General Public
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// License along with this library; if not, write to the
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// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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// Boston, MA 02111-1307, USA.
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//
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// $Id$
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#ifndef _SG_CONSTANTS_H
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#define _SG_CONSTANTS_H
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <simgear/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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# ifdef FG_MATH_EXCEPTION_CLASH
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# define exception C_exception
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# endif
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# include <math.h>
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#endif
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// Make sure PI is defined in its various forms
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// PI, only PI, and nothing but PI
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#ifdef M_PI
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# define FG_PI M_PI
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#else
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# define FG_PI 3.14159265358979323846
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#endif
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// 2 * PI
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#define FG_2PI 6.28318530717958647692
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// PI / 2
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#ifdef M_PI_2
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# define FG_PI_2 M_PI_2
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#else
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# define FG_PI_2 1.57079632679489661923
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#endif
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// PI / 4
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#define FG_PI_4 0.78539816339744830961
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#ifndef M_E
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# define M_E 2.7182818284590452354
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#endif
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// ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator
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#define ONE_SECOND 4.848136811E-6
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// Radius of Earth in kilometers at the equator. Another source had
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// 6378.165 but this is probably close enough
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#define EARTH_RAD 6378.155
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// Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
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// Value of earth radius from [8]
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#define EQUATORIAL_RADIUS_FT 20925650. // ft
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#define EQUATORIAL_RADIUS_M 6378138.12 // meter
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// Radius squared
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#define RESQ_FT 437882827922500. // ft
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#define RESQ_M 40680645877797.1344 // meter
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#if 0
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// Value of earth flattening parameter from ref [8]
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//
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// Note: FP = f
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// E = 1-f
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// EPS = sqrt(1-(1-f)^2)
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//
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#define FP 0.003352813178
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#define E 0.996647186
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#define EPS 0.081819221
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#define INVG 0.031080997
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// Time Related Parameters
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#define MJD0 2415020.0
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#define J2000 (2451545.0 - MJD0)
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#define SIDRATE .9972695677
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#endif
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// Conversions
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// Degrees to Radians
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#define DEG_TO_RAD 0.017453292 // deg*pi/180 = rad
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// Radians to Degrees
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#define RAD_TO_DEG 57.29577951 // rad*180/pi = deg
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// Arc seconds to radians // (arcsec*pi)/(3600*180) = rad
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#define ARCSEC_TO_RAD 4.84813681109535993589e-06
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// Radians to arc seconds // (rad*3600*180)/pi = arcsec
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#define RAD_TO_ARCSEC 206264.806247096355156
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// Feet to Meters
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#define FEET_TO_METER 0.3048
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// Meters to Feet
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#define METER_TO_FEET 3.28083989501312335958
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// Meters to Nautical Miles, 1 nm = 6076.11549 feet
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#define METER_TO_NM 0.00053995680
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// Nautical Miles to Meters
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#define NM_TO_METER 1852.0000
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// Radians to Nautical Miles, 1 nm = 1/60 of a degree
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#define NM_TO_RAD 0.00029088820866572159
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// Nautical Miles to Radians
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#define RAD_TO_NM 3437.7467707849392526
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// For divide by zero avoidance, this will be close enough to zero
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#define FG_EPSILON 0.0000001
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#endif // _SG_CONSTANTS_H
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