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
33 #include <simgear/compiler.h>
35 #ifdef SG_HAVE_STD_INCLUDES
38 # ifdef SG_MATH_EXCEPTION_CLASH
39 # define exception C_exception
47 // Make sure PI is defined in its various forms
49 // SG_PI and SGD_PI (float and double) come from plib/sg.h
52 #define SGD_2PI 6.28318530717958647692
56 # define SGD_PI_2 M_PI_2
58 # define SGD_PI_2 1.57079632679489661923
62 #define SGD_PI_4 0.78539816339744830961
68 # define SG_E 2.7182818284590452354
71 /** pi/180/60/60, or about 100 feet at earths' equator */
72 #define SG_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 SG_EARTH_RAD 6378.155
80 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
82 /** Value of earth radius from LaRCsim (ft) */
83 #define SG_EQUATORIAL_RADIUS_FT 20925650.
85 /** Value of earth radius from LaRCsim (meter) */
86 #define SG_EQUATORIAL_RADIUS_M 6378138.12
88 /** Radius squared (ft) */
89 #define SG_EQ_RAD_SQUARE_FT 437882827922500.
91 /** Radius squared (meter) */
92 #define SG_EQ_RAD_SQUARE_M 40680645877797.1344
96 /** Arc seconds to radians. (arcsec*pi)/(3600*180) = rad */
97 #define SG_ARCSEC_TO_RAD 4.84813681109535993589e-06
99 /** Radians to arc seconds. (rad*3600*180)/pi = arcsec */
100 #define SG_RAD_TO_ARCSEC 206264.806247096355156
102 /** Feet to Meters */
103 #define SG_FEET_TO_METER 0.3048
105 /** Meters to Feet */
106 #define SG_METER_TO_FEET 3.28083989501312335958
108 /** Meters to Nautical Miles. 1 nm = 6076.11549 feet */
109 #define SG_METER_TO_NM 0.00053995680
111 /** Nautical Miles to Meters */
112 #define SG_NM_TO_METER 1852.0000
114 /** Radians to Nautical Miles. 1 nm = 1/60 of a degree */
115 #define SG_NM_TO_RAD 0.00029088820866572159
117 /** Nautical Miles to Radians */
118 #define SG_RAD_TO_NM 3437.7467707849392526
120 /** For divide by zero avoidance, this will be close enough to zero */
121 #define SG_EPSILON 0.0000001
124 /** Highest binobj format version we know how to read/write. This starts at
125 * 0 and can go up to 65535 */
126 #define SG_BINOBJ_VERSION 6
128 /** for backwards compatibility */
129 #define SG_SCENERY_FILE_FORMAT "0.4"
132 #endif // _SG_CONSTANTS_H