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 * Various constant definitions.
29 #ifndef _SG_CONSTANTS_H
30 #define _SG_CONSTANTS_H
37 #include <simgear/compiler.h>
39 #ifdef SG_HAVE_STD_INCLUDES
42 # ifdef SG_MATH_EXCEPTION_CLASH
43 # define exception C_exception
49 // Make sure PI is defined in its various forms
51 // PI, only PI, and nothing but PI
55 # define SG_PI 3.14159265358979323846
59 #define SG_2PI 6.28318530717958647692
63 # define SG_PI_2 M_PI_2
65 # define SG_PI_2 1.57079632679489661923
69 #define SG_PI_4 0.78539816339744830961
72 # define M_E 2.7182818284590452354
75 // ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator
76 #define ONE_SECOND 4.848136811E-6
79 // Radius of Earth in kilometers at the equator. Another source had
80 // 6378.165 but this is probably close enough
81 #define EARTH_RAD 6378.155
84 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
86 // Value of earth radius from [8]
87 #define EQUATORIAL_RADIUS_FT 20925650. // ft
88 #define EQUATORIAL_RADIUS_M 6378138.12 // meter
90 #define RESQ_FT 437882827922500. // ft
91 #define RESQ_M 40680645877797.1344 // meter
94 // Value of earth flattening parameter from ref [8]
98 // EPS = sqrt(1-(1-f)^2)
101 #define FP 0.003352813178
102 #define E 0.996647186
103 #define EPS 0.081819221
104 #define INVG 0.031080997
106 // Time Related Parameters
108 #define MJD0 2415020.0
109 #define J2000 (2451545.0 - MJD0)
110 #define SIDRATE .9972695677
115 // Degrees to Radians
116 #define DEG_TO_RAD 0.017453292 // deg*pi/180 = rad
118 // Radians to Degrees
119 #define RAD_TO_DEG 57.29577951 // rad*180/pi = deg
121 // Arc seconds to radians // (arcsec*pi)/(3600*180) = rad
122 #define ARCSEC_TO_RAD 4.84813681109535993589e-06
124 // Radians to arc seconds // (rad*3600*180)/pi = arcsec
125 #define RAD_TO_ARCSEC 206264.806247096355156
128 #define FEET_TO_METER 0.3048
131 #define METER_TO_FEET 3.28083989501312335958
133 // Meters to Nautical Miles, 1 nm = 6076.11549 feet
134 #define METER_TO_NM 0.00053995680
136 // Nautical Miles to Meters
137 #define NM_TO_METER 1852.0000
139 // Radians to Nautical Miles, 1 nm = 1/60 of a degree
140 #define NM_TO_RAD 0.00029088820866572159
142 // Nautical Miles to Radians
143 #define RAD_TO_NM 3437.7467707849392526
145 // For divide by zero avoidance, this will be close enough to zero
146 #define SG_EPSILON 0.0000001
149 // Highest binobj format version we know how to read/write. This starts at
150 // 0 and can go up to 65535
151 #define SG_BINOBJ_VERSION 5
152 // for backwards compatibility
153 #define SG_SCENERY_FILE_FORMAT "0.4"
156 #endif // _SG_CONSTANTS_H