1 // constants.h -- various constant definitions
3 // Written by Curtis Olson, started February 2000.
5 // Copyright (C) 2000 Curtis L. Olson - curt@flightgear.org
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 #ifndef _SG_CONSTANTS_H
25 #define _SG_CONSTANTS_H
32 #include <simgear/compiler.h>
34 #ifdef FG_HAVE_STD_INCLUDES
37 # ifdef FG_MATH_EXCEPTION_CLASH
38 # define exception C_exception
44 // Make sure PI is defined in its various forms
46 // PI, only PI, and nothing but PI
50 # define FG_PI 3.14159265358979323846
54 #define FG_2PI 6.28318530717958647692
58 # define FG_PI_2 M_PI_2
60 # define FG_PI_2 1.57079632679489661923
64 #define FG_PI_4 0.78539816339744830961
67 # define M_E 2.7182818284590452354
70 // ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator
71 #define ONE_SECOND 4.848136811E-6
74 // Radius of Earth in kilometers at the equator. Another source had
75 // 6378.165 but this is probably close enough
76 #define EARTH_RAD 6378.155
79 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
81 // Value of earth radius from [8]
82 #define EQUATORIAL_RADIUS_FT 20925650. // ft
83 #define EQUATORIAL_RADIUS_M 6378138.12 // meter
85 #define RESQ_FT 437882827922500. // ft
86 #define RESQ_M 40680645877797.1344 // meter
88 // Value of earth flattening parameter from ref [8]
92 // EPS = sqrt(1-(1-f)^2)
95 #define FP 0.003352813178
97 #define EPS 0.081819221
98 #define INVG 0.031080997
100 // Time Related Parameters
102 #define MJD0 2415020.0
103 #define J2000 (2451545.0 - MJD0)
104 #define SIDRATE .9972695677
109 // Degrees to Radians
110 #define DEG_TO_RAD 0.017453292 // deg*pi/180 = rad
112 // Radians to Degrees
113 #define RAD_TO_DEG 57.29577951 // rad*180/pi = deg
115 // Arc seconds to radians // (arcsec*pi)/(3600*180) = rad
116 #define ARCSEC_TO_RAD 4.84813681109535993589e-06
118 // Radians to arc seconds // (rad*3600*180)/pi = arcsec
119 #define RAD_TO_ARCSEC 206264.806247096355156
122 #define FEET_TO_METER 0.3048
125 #define METER_TO_FEET 3.28083989501312335958
127 // Meters to Nautical Miles, 1 nm = 6076.11549 feet
128 #define METER_TO_NM 0.00053995680
130 // Nautical Miles to Meters
131 #define NM_TO_METER 1852.0000
133 // Radians to Nautical Miles, 1 nm = 1/60 of a degree
134 #define NM_TO_RAD 0.00029088820866572159
136 // Nautical Miles to Radians
137 #define RAD_TO_NM 3437.7467707849392526
139 // For divide by zero avoidance, this will be close enough to zero
140 #define FG_EPSILON 0.0000001
143 #endif // _SG_CONSTANTS_H