1 // constants.h -- various constant definitions
3 // Written by Curtis Olson, started February 2000.
5 // Copyright (C) 2000 Curtis L. Olson - http://www.flightgear.org/~curt/
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 General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
24 * Various constant definitions.
28 #ifndef _SG_CONSTANTS_H
29 #define _SG_CONSTANTS_H
32 #include <simgear/compiler.h>
37 // Make sure PI is defined in its various forms
43 #define SG_PI 3.1415926535f
44 #define SGD_PI 3.1415926535
50 #define SGD_2PI SGD_PI * 2.0
54 # define SGD_PI_2 M_PI_2
56 # define SGD_PI_2 1.57079632679489661923
60 #define SGD_PI_4 0.78539816339744830961
63 #define SGD_DEGREES_TO_RADIANS (SGD_PI/180.0)
64 #define SGD_RADIANS_TO_DEGREES (180.0/SGD_PI)
66 #define SG_DEGREES_TO_RADIANS SGD_DEGREES_TO_RADIANS
67 #define SG_RADIANS_TO_DEGREES SGD_RADIANS_TO_DEGREES
73 # define SG_E 2.7182818284590452354
76 /** pi/180/60/60, or about 100 feet at earths' equator */
77 #define SG_ONE_SECOND 4.848136811E-6
80 /** Radius of Earth in kilometers at the equator. Another source had
81 * 6378.165 but this is probably close enough */
82 #define SG_EARTH_RAD 6378.155
84 // Maximum terrain elevation from sea level
85 #define SG_MAX_ELEVATION_M 9000.0
87 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
89 /** Value of earth radius from LaRCsim (ft) */
90 #define SG_EQUATORIAL_RADIUS_FT 20925650.
92 /** Value of earth radius from LaRCsim (meter) */
93 #define SG_EQUATORIAL_RADIUS_M 6378138.12
95 /** Radius squared (ft) */
96 #define SG_EQ_RAD_SQUARE_FT 437882827922500.
98 /** Radius squared (meter) */
99 #define SG_EQ_RAD_SQUARE_M 40680645877797.1344
103 /** Arc seconds to radians. (arcsec*pi)/(3600*180) = rad */
104 #define SG_ARCSEC_TO_RAD 4.84813681109535993589e-06
106 /** Radians to arc seconds. (rad*3600*180)/pi = arcsec */
107 #define SG_RAD_TO_ARCSEC 206264.806247096355156
109 /** Feet to Meters */
110 #define SG_FEET_TO_METER 0.3048
112 /** Meters to Feet */
113 #define SG_METER_TO_FEET 3.28083989501312335958
115 /** Meters to Nautical Miles. 1 nm = 6076.11549 feet */
116 #define SG_METER_TO_NM 0.0005399568034557235
118 /** Nautical Miles to Meters */
119 #define SG_NM_TO_METER 1852.0000
121 /** Meters to Statute Miles. */
122 #define SG_METER_TO_SM 0.0006213699494949496
124 /** Statute Miles to Meters. */
125 #define SG_SM_TO_METER 1609.3412196
127 /** Radians to Nautical Miles. 1 nm = 1/60 of a degree */
128 #define SG_NM_TO_RAD 0.00029088820866572159
130 /** Nautical Miles to Radians */
131 #define SG_RAD_TO_NM 3437.7467707849392526
133 /** meters per second to Knots */
134 #define SG_MPS_TO_KT 1.9438444924406046432
136 /** Knots to meters per second */
137 #define SG_KT_TO_MPS 0.5144444444444444444
139 /** Feet per second to Knots */
140 #define SG_FPS_TO_KT 0.5924838012958962841
142 /** Knots to Feet per second */
143 #define SG_KT_TO_FPS 1.6878098571011956874
145 /** meters per second to Miles per hour */
146 #define SG_MPS_TO_MPH 2.2369362920544020312
148 /** meetrs per hour to Miles per second */
149 #define SG_MPH_TO_MPS 0.44704
151 /** Meters per second to Kilometers per hour */
152 #define SG_MPS_TO_KMH 3.6
154 /** Kilometers per hour to meters per second */
155 #define SG_KMH_TO_MPS 0.2777777777777777778
157 /** Pascal to Inch Mercury */
158 #define SG_PA_TO_INHG 0.0002952998330101010
160 /** Inch Mercury to Pascal */
161 #define SG_INHG_TO_PA 3386.388640341
164 /** For divide by zero avoidance, this will be close enough to zero */
165 #define SG_EPSILON 0.0000001
167 /** Highest binobj format version we know how to read/write. This starts at
168 * 0 and can go up to 65535 */
169 #define SG_BINOBJ_VERSION 6
171 /** for backwards compatibility */
172 #define SG_SCENERY_FILE_FORMAT "0.4"
175 #endif // _SG_CONSTANTS_H