221 lines
5.9 KiB
C
221 lines
5.9 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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// Last change by Eric van den Berg, Feb 2013
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//
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// Copyright (C) 2000 Curtis L. Olson - http://www.flightgear.org/~curt/
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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 General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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//
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// $Id$
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/** \file constants.h
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* Various constant definitions.
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*/
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#ifndef _SG_CONSTANTS_H
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#define _SG_CONSTANTS_H
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#include <simgear/compiler.h>
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#include <cmath>
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// Make sure PI is defined in its various forms
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#ifndef SGD_PI // remove me once FlightGear no longer uses PLIB
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#ifdef M_PI
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const double SGD_PI = M_PI;
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const float SG_PI = M_PI;
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#else
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const float SG_PI = 3.1415926535f;
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const double SGD_PI = 3.1415926535;
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#endif
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#endif // of PLIB-SG guard
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/** 2 * PI */
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const double SGD_2PI = SGD_PI * 2.0;
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/** PI / 2 */
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#ifdef M_PI_2
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# define SGD_PI_2 M_PI_2
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#else
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# define SGD_PI_2 1.57079632679489661923
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#endif
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/** PI / 4 */
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const double SGD_PI_4 = 0.78539816339744830961;
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#ifndef SGD_DEGREES_TO_RADIANS // // remove me once FlightGear no longer uses PLIB
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const double SGD_DEGREES_TO_RADIANS = SGD_PI / 180.0;
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const double SGD_RADIANS_TO_DEGREES = 180.0 / SGD_PI;
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const float SG_DEGREES_TO_RADIANS = SG_PI / 180.0f;
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const float SG_RADIANS_TO_DEGREES = 180.0f / SG_PI;
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#endif // of PLIB-SG guard
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/** \def SG_E "e" */
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#ifdef M_E
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# define SG_E M_E
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#else
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# define SG_E 2.7182818284590452354
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#endif
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/** pi/180/60/60, or about 100 feet at earths' equator */
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#define SG_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 SG_EARTH_RAD 6378.155
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// Maximum terrain elevation from sea level
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#define SG_MAX_ELEVATION_M 9000.0
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// Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
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/** Value of earth radius from LaRCsim (ft) */
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#define SG_EQUATORIAL_RADIUS_FT 20925650.
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/** Value of earth radius from LaRCsim (meter) */
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#define SG_EQUATORIAL_RADIUS_M 6378138.12
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/** Radius squared (ft) */
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#define SG_EQ_RAD_SQUARE_FT 437882827922500.
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/** Radius squared (meter) */
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#define SG_EQ_RAD_SQUARE_M 40680645877797.1344
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// Physical Constants, SI
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/**mean gravity on earth */
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#define SG_g0_m_p_s2 9.80665 // m/s2
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/**standard pressure at SL */
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#define SG_p0_Pa 101325.0 // Pa
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/**standard density at SL */
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#define SG_rho0_kg_p_m3 1.225 // kg/m3
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/**standard temperature at SL */
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#define SG_T0_K 288.15 // K (=15degC)
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/**specific gas constant of air*/
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#define SG_R_m2_p_s2_p_K 287.05 // m2/s2/K
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/**specific heat constant at constant pressure*/
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#define SG_cp_m2_p_s2_p_K 1004.68 // m2/s2/K
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/**ratio of specific heats of air*/
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#define SG_gamma 1.4 // =cp/cv (cp = 1004.68 m2/s2 K , cv = 717.63 m2/s2 K)
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/**constant beta used to calculate dynamic viscosity */
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#define SG_beta_kg_p_sm_sqrK 1.458e-06 // kg/s/m/SQRT(K)
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/** Sutherland constant */
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#define SG_S_K 110.4 // K
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// Conversions
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/** Arc seconds to radians. (arcsec*pi)/(3600*180) = rad */
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#define SG_ARCSEC_TO_RAD 4.84813681109535993589e-06
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/** Radians to arc seconds. (rad*3600*180)/pi = arcsec */
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#define SG_RAD_TO_ARCSEC 206264.806247096355156
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/** Feet to Meters */
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#define SG_FEET_TO_METER 0.3048
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/** Meters to Feet */
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#define SG_METER_TO_FEET 3.28083989501312335958
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/** Meters to Nautical Miles. 1 nm = 6076.11549 feet */
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#define SG_METER_TO_NM 0.0005399568034557235
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/** Nautical Miles to Meters */
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#define SG_NM_TO_METER 1852.0000
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/** Meters to Statute Miles. */
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#define SG_METER_TO_SM 0.0006213699494949496
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/** Statute Miles to Meters. */
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#define SG_SM_TO_METER 1609.3412196
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/** Radians to Nautical Miles. 1 nm = 1/60 of a degree */
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#define SG_NM_TO_RAD 0.00029088820866572159
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/** Nautical Miles to Radians */
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#define SG_RAD_TO_NM 3437.7467707849392526
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/** meters per second to Knots */
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#define SG_MPS_TO_KT 1.9438444924406046432
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/** Knots to meters per second */
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#define SG_KT_TO_MPS 0.5144444444444444444
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/** Feet per second to Knots */
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#define SG_FPS_TO_KT 0.5924838012958962841
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/** Knots to Feet per second */
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#define SG_KT_TO_FPS 1.6878098571011956874
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/** meters per second to Miles per hour */
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#define SG_MPS_TO_MPH 2.2369362920544020312
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/** meetrs per hour to Miles per second */
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#define SG_MPH_TO_MPS 0.44704
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/** Meters per second to Kilometers per hour */
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#define SG_MPS_TO_KMH 3.6
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/** Kilometers per hour to meters per second */
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#define SG_KMH_TO_MPS 0.2777777777777777778
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/** Pascal to Inch Mercury */
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#define SG_PA_TO_INHG 0.0002952998330101010
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/** Inch Mercury to Pascal */
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#define SG_INHG_TO_PA 3386.388640341
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/** slug/ft3 to kg/m3 */
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#define SG_SLUGFT3_TO_KGPM3 515.379
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/** For divide by zero avoidance, this will be close enough to zero */
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#define SG_EPSILON 0.0000001
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/** Highest binobj format version we know how to read/write. This starts at
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* 0 and can go up to 65535 */
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#define SG_BINOBJ_VERSION 6
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/** for backwards compatibility */
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#define SG_SCENERY_FILE_FORMAT "0.4"
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/** Default range in m at which all objects are displayed. Overridden by /sim/rendering/static-lod/rough **/
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#define SG_OBJECT_RANGE 9000.0
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/** Radius of scenery tiles in m **/
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#define SG_TILE_RADIUS 14000.0
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#endif // _SG_CONSTANTS_H
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