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
51 // Make sure PI is defined in its various forms
53 // SG_PI and SGD_PI (float and double) come from plib/sg.h
56 #define SGD_2PI 6.28318530717958647692
60 # define SGD_PI_2 M_PI_2
62 # define SGD_PI_2 1.57079632679489661923
66 #define SGD_PI_4 0.78539816339744830961
69 # define M_E 2.7182818284590452354
72 // SG_ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator
73 #define SG_ONE_SECOND 4.848136811E-6
76 // Radius of Earth in kilometers at the equator. Another source had
77 // 6378.165 but this is probably close enough
78 #define SG_EARTH_RAD 6378.155
81 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
83 // Value of earth radius from [8]
84 #define SG_EQUATORIAL_RADIUS_FT 20925650. // ft
85 #define SG_EQUATORIAL_RADIUS_M 6378138.12 // meter
87 #define SG_EQ_RAD_SQUARE_FT 437882827922500. // ft
88 #define SG_EQ_RAD_SQUARE_M 40680645877797.1344 // meter
92 // Arc seconds to radians // (arcsec*pi)/(3600*180) = rad
93 #define SG_ARCSEC_TO_RAD 4.84813681109535993589e-06
95 // Radians to arc seconds // (rad*3600*180)/pi = arcsec
96 #define SG_RAD_TO_ARCSEC 206264.806247096355156
99 #define SG_FEET_TO_METER 0.3048
102 #define SG_METER_TO_FEET 3.28083989501312335958
104 // Meters to Nautical Miles, 1 nm = 6076.11549 feet
105 #define SG_METER_TO_NM 0.00053995680
107 // Nautical Miles to Meters
108 #define SG_NM_TO_METER 1852.0000
110 // Radians to Nautical Miles, 1 nm = 1/60 of a degree
111 #define SG_NM_TO_RAD 0.00029088820866572159
113 // Nautical Miles to Radians
114 #define SG_RAD_TO_NM 3437.7467707849392526
116 // For divide by zero avoidance, this will be close enough to zero
117 #define SG_EPSILON 0.0000001
120 // Highest binobj format version we know how to read/write. This starts at
121 // 0 and can go up to 65535
122 #define SG_BINOBJ_VERSION 5
123 // for backwards compatibility
124 #define SG_SCENERY_FILE_FORMAT "0.4"
127 #endif // _SG_CONSTANTS_H