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 library is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU Library General Public
9 // License as published by the Free Software Foundation; either
10 // version 2 of the License, or (at your option) any later version.
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // Library General Public License for more details.
17 // You should have received a copy of the GNU Library General Public
18 // License along with this library; if not, write to the
19 // Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 // Boston, MA 02111-1307, USA.
25 #ifndef _SG_CONSTANTS_H
26 #define _SG_CONSTANTS_H
33 #include <simgear/compiler.h>
35 #ifdef FG_HAVE_STD_INCLUDES
38 # ifdef FG_MATH_EXCEPTION_CLASH
39 # define exception C_exception
45 // Make sure PI is defined in its various forms
47 // PI, only PI, and nothing but PI
51 # define FG_PI 3.14159265358979323846
55 #define FG_2PI 6.28318530717958647692
59 # define FG_PI_2 M_PI_2
61 # define FG_PI_2 1.57079632679489661923
65 #define FG_PI_4 0.78539816339744830961
68 # define M_E 2.7182818284590452354
71 // ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator
72 #define ONE_SECOND 4.848136811E-6
75 // Radius of Earth in kilometers at the equator. Another source had
76 // 6378.165 but this is probably close enough
77 #define EARTH_RAD 6378.155
80 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
82 // Value of earth radius from [8]
83 #define EQUATORIAL_RADIUS_FT 20925650. // ft
84 #define EQUATORIAL_RADIUS_M 6378138.12 // meter
86 #define RESQ_FT 437882827922500. // ft
87 #define RESQ_M 40680645877797.1344 // meter
90 // Value of earth flattening parameter from ref [8]
94 // EPS = sqrt(1-(1-f)^2)
97 #define FP 0.003352813178
99 #define EPS 0.081819221
100 #define INVG 0.031080997
102 // Time Related Parameters
104 #define MJD0 2415020.0
105 #define J2000 (2451545.0 - MJD0)
106 #define SIDRATE .9972695677
111 // Degrees to Radians
112 #define DEG_TO_RAD 0.017453292 // deg*pi/180 = rad
114 // Radians to Degrees
115 #define RAD_TO_DEG 57.29577951 // rad*180/pi = deg
117 // Arc seconds to radians // (arcsec*pi)/(3600*180) = rad
118 #define ARCSEC_TO_RAD 4.84813681109535993589e-06
120 // Radians to arc seconds // (rad*3600*180)/pi = arcsec
121 #define RAD_TO_ARCSEC 206264.806247096355156
124 #define FEET_TO_METER 0.3048
127 #define METER_TO_FEET 3.28083989501312335958
129 // Meters to Nautical Miles, 1 nm = 6076.11549 feet
130 #define METER_TO_NM 0.00053995680
132 // Nautical Miles to Meters
133 #define NM_TO_METER 1852.0000
135 // Radians to Nautical Miles, 1 nm = 1/60 of a degree
136 #define NM_TO_RAD 0.00029088820866572159
138 // Nautical Miles to Radians
139 #define RAD_TO_NM 3437.7467707849392526
141 // For divide by zero avoidance, this will be close enough to zero
142 #define FG_EPSILON 0.0000001
145 #endif // _SG_CONSTANTS_H