1 // constants.h -- various constant definitions
3 // Written by Curtis Olson, started February 2000.
4 // Last change by Eric van den Berg, Feb 2013
6 // Copyright (C) 2000 Curtis L. Olson - http://www.flightgear.org/~curt/
8 // This library is free software; you can redistribute it and/or
9 // modify it under the terms of the GNU Library General Public
10 // License as published by the Free Software Foundation; either
11 // version 2 of the License, or (at your option) any later version.
13 // This library is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 // Library General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
25 * Various constant definitions.
29 #ifndef _SG_CONSTANTS_H
30 #define _SG_CONSTANTS_H
33 #include <simgear/compiler.h>
38 // Make sure PI is defined in its various forms
40 #ifndef SGD_PI // remove me once FlightGear no longer uses PLIB
43 const double SGD_PI = M_PI;
44 const float SG_PI = M_PI;
46 const float SG_PI = 3.1415926535f;
47 const double SGD_PI = 3.1415926535;
50 #endif // of PLIB-SG guard
53 const double SGD_2PI = SGD_PI * 2.0;
57 # define SGD_PI_2 M_PI_2
59 # define SGD_PI_2 1.57079632679489661923
63 const double SGD_PI_4 = 0.78539816339744830961;
65 #ifndef SGD_DEGREES_TO_RADIANS // // remove me once FlightGear no longer uses PLIB
67 const double SGD_DEGREES_TO_RADIANS = SGD_PI / 180.0;
68 const double SGD_RADIANS_TO_DEGREES = 180.0 / SGD_PI;
70 const float SG_DEGREES_TO_RADIANS = SG_PI / 180.0f;
71 const float SG_RADIANS_TO_DEGREES = 180.0f / SG_PI;
73 #endif // of PLIB-SG guard
79 # define SG_E 2.7182818284590452354
82 /** pi/180/60/60, or about 100 feet at earths' equator */
83 #define SG_ONE_SECOND 4.848136811E-6
86 /** Radius of Earth in kilometers at the equator. Another source had
87 * 6378.165 but this is probably close enough */
88 #define SG_EARTH_RAD 6378.155
90 // Maximum terrain elevation from sea level
91 #define SG_MAX_ELEVATION_M 9000.0
93 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
95 /** Value of earth radius from LaRCsim (ft) */
96 #define SG_EQUATORIAL_RADIUS_FT 20925650.
98 /** Value of earth radius from LaRCsim (meter) */
99 #define SG_EQUATORIAL_RADIUS_M 6378138.12
101 /** Radius squared (ft) */
102 #define SG_EQ_RAD_SQUARE_FT 437882827922500.
104 /** Radius squared (meter) */
105 #define SG_EQ_RAD_SQUARE_M 40680645877797.1344
108 // Physical Constants, SI
110 /**mean gravity on earth */
111 #define SG_g0_m_p_s2 9.80665 // m/s2
113 /**standard pressure at SL */
114 #define SG_p0_Pa 101325.0 // Pa
116 /**standard density at SL */
117 #define SG_rho0_kg_p_m3 1.225 // kg/m3
119 /**standard temperature at SL */
120 #define SG_T0_K 288.15 // K (=15degC)
122 /**specific gas constant of air*/
123 #define SG_R_m2_p_s2_p_K 287.05 // m2/s2/K
125 /**specific heat constant at constant pressure*/
126 #define SG_cp_m2_p_s2_p_K 1004.68 // m2/s2/K
128 /**ratio of specific heats of air*/
129 #define SG_gamma 1.4 // =cp/cv (cp = 1004.68 m2/s2 K , cv = 717.63 m2/s2 K)
131 /**constant beta used to calculate dynamic viscosity */
132 #define SG_beta_kg_p_sm_sqrK 1.458e-06 // kg/s/m/SQRT(K)
134 /** Sutherland constant */
135 #define SG_S_K 110.4 // K
140 /** Arc seconds to radians. (arcsec*pi)/(3600*180) = rad */
141 #define SG_ARCSEC_TO_RAD 4.84813681109535993589e-06
143 /** Radians to arc seconds. (rad*3600*180)/pi = arcsec */
144 #define SG_RAD_TO_ARCSEC 206264.806247096355156
146 /** Feet to Meters */
147 #define SG_FEET_TO_METER 0.3048
149 /** Meters to Feet */
150 #define SG_METER_TO_FEET 3.28083989501312335958
152 /** Meters to Nautical Miles. 1 nm = 6076.11549 feet */
153 #define SG_METER_TO_NM 0.0005399568034557235
155 /** Nautical Miles to Meters */
156 #define SG_NM_TO_METER 1852.0000
158 /** Meters to Statute Miles. */
159 #define SG_METER_TO_SM 0.0006213699494949496
161 /** Statute Miles to Meters. */
162 #define SG_SM_TO_METER 1609.3412196
164 /** Radians to Nautical Miles. 1 nm = 1/60 of a degree */
165 #define SG_NM_TO_RAD 0.00029088820866572159
167 /** Nautical Miles to Radians */
168 #define SG_RAD_TO_NM 3437.7467707849392526
170 /** meters per second to Knots */
171 #define SG_MPS_TO_KT 1.9438444924406046432
173 /** Knots to meters per second */
174 #define SG_KT_TO_MPS 0.5144444444444444444
176 /** Feet per second to Knots */
177 #define SG_FPS_TO_KT 0.5924838012958962841
179 /** Knots to Feet per second */
180 #define SG_KT_TO_FPS 1.6878098571011956874
182 /** meters per second to Miles per hour */
183 #define SG_MPS_TO_MPH 2.2369362920544020312
185 /** meetrs per hour to Miles per second */
186 #define SG_MPH_TO_MPS 0.44704
188 /** Meters per second to Kilometers per hour */
189 #define SG_MPS_TO_KMH 3.6
191 /** Kilometers per hour to meters per second */
192 #define SG_KMH_TO_MPS 0.2777777777777777778
194 /** Pascal to Inch Mercury */
195 #define SG_PA_TO_INHG 0.0002952998330101010
197 /** Inch Mercury to Pascal */
198 #define SG_INHG_TO_PA 3386.388640341
200 /** slug/ft3 to kg/m3 */
201 #define SG_SLUGFT3_TO_KGPM3 515.379
204 /** For divide by zero avoidance, this will be close enough to zero */
205 #define SG_EPSILON 0.0000001
207 /** Highest binobj format version we know how to read/write. This starts at
208 * 0 and can go up to 65535 */
209 #define SG_BINOBJ_VERSION 6
211 /** for backwards compatibility */
212 #define SG_SCENERY_FILE_FORMAT "0.4"
215 #endif // _SG_CONSTANTS_H