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>
40 // Make sure PI is defined in its various forms
42 // SG_PI and SGD_PI (float and double) come from plib/sg.h
45 #define SGD_2PI 6.28318530717958647692
49 # define SGD_PI_2 M_PI_2
51 # define SGD_PI_2 1.57079632679489661923
55 #define SGD_PI_4 0.78539816339744830961
61 # define SG_E 2.7182818284590452354
64 /** pi/180/60/60, or about 100 feet at earths' equator */
65 #define SG_ONE_SECOND 4.848136811E-6
68 /** Radius of Earth in kilometers at the equator. Another source had
69 * 6378.165 but this is probably close enough */
70 #define SG_EARTH_RAD 6378.155
72 // Maximum terrain elevation from sea level
73 #define SG_MAX_ELEVATION_M 9000.0
75 // Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h
77 /** Value of earth radius from LaRCsim (ft) */
78 #define SG_EQUATORIAL_RADIUS_FT 20925650.
80 /** Value of earth radius from LaRCsim (meter) */
81 #define SG_EQUATORIAL_RADIUS_M 6378138.12
83 /** Radius squared (ft) */
84 #define SG_EQ_RAD_SQUARE_FT 437882827922500.
86 /** Radius squared (meter) */
87 #define SG_EQ_RAD_SQUARE_M 40680645877797.1344
91 /** Arc seconds to radians. (arcsec*pi)/(3600*180) = rad */
92 #define SG_ARCSEC_TO_RAD 4.84813681109535993589e-06
94 /** Radians to arc seconds. (rad*3600*180)/pi = arcsec */
95 #define SG_RAD_TO_ARCSEC 206264.806247096355156
98 #define SG_FEET_TO_METER 0.3048
100 /** Meters to Feet */
101 #define SG_METER_TO_FEET 3.28083989501312335958
103 /** Meters to Nautical Miles. 1 nm = 6076.11549 feet */
104 #define SG_METER_TO_NM 0.0005399568034557235
106 /** Nautical Miles to Meters */
107 #define SG_NM_TO_METER 1852.0000
109 /** Meters to Statute Miles. */
110 #define SG_METER_TO_SM 0.0006213699494949496
112 /** Statute Miles to Meters. */
113 #define SG_SM_TO_METER 1609.3412196
115 /** Radians to Nautical Miles. 1 nm = 1/60 of a degree */
116 #define SG_NM_TO_RAD 0.00029088820866572159
118 /** Nautical Miles to Radians */
119 #define SG_RAD_TO_NM 3437.7467707849392526
121 /** meters per second to Knots */
122 #define SG_MPS_TO_KT 1.9438444924406046432
124 /** Knots to meters per second */
125 #define SG_KT_TO_MPS 0.5144444444444444444
127 /** Feet per second to Knots */
128 #define SG_FPS_TO_KT 0.5924838012958962841
130 /** Knots to Feet per second */
131 #define SG_KT_TO_FPS 1.6878098571011956874
133 /** meters per second to Miles per hour */
134 #define SG_MPS_TO_MPH 2.2369362920544020312
136 /** meetrs per hour to Miles per second */
137 #define SG_MPH_TO_MPS 0.44704
139 /** Meters per second to Kilometers per hour */
140 #define SG_MPS_TO_KMH 3.6
142 /** Kilometers per hour to meters per second */
143 #define SG_KMH_TO_MPS 0.2777777777777777778
145 /** Pascal to Inch Mercury */
146 #define SG_PA_TO_INHG 0.0002952998330101010
148 /** Inch Mercury to Pascal */
149 #define SG_INHG_TO_PA 3386.388640341
152 /** For divide by zero avoidance, this will be close enough to zero */
153 #define SG_EPSILON 0.0000001
155 /** Highest binobj format version we know how to read/write. This starts at
156 * 0 and can go up to 65535 */
157 #define SG_BINOBJ_VERSION 6
159 /** for backwards compatibility */
160 #define SG_SCENERY_FILE_FORMAT "0.4"
163 #endif // _SG_CONSTANTS_H