GeographicLib: Constants.hpp Source File

GeographicLib 2.7

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Constants.hpp
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1/**
2 * \file Constants.hpp
3 * \brief Header for GeographicLib::Constants class
4 *
5 * Copyright (c) Charles Karney (2008-2024) <karney@alum.mit.edu> and licensed
6 * under the MIT/X11 License. For more information, see
7 * https://geographiclib.sourceforge.io/
8 **********************************************************************/
9
10#if !defined(GEOGRAPHICLIB_CONSTANTS_HPP)
11#define GEOGRAPHICLIB_CONSTANTS_HPP 1
12
13#include <GeographicLib/Config.h>
14
15/**
16 * @relates GeographicLib::Constants
17 * Pack the version components into a single integer. Users should not rely on
18 * this particular packing of the components of the version number; see the
19 * documentation for GEOGRAPHICLIB_VERSION, below.
20 **********************************************************************/
21#define GEOGRAPHICLIB_VERSION_NUM(a,b,c) ((((a) * 10000 + (b)) * 100) + (c))
22
23/**
24 * @relates GeographicLib::Constants
25 * The version of GeographicLib as a single integer, packed as MMmmmmpp where
26 * MM is the major version, mmmm is the minor version, and pp is the patch
27 * level. Users should not rely on this particular packing of the components
28 * of the version number. Instead they should use a test such as \code
29 #if GEOGRAPHICLIB_VERSION >= GEOGRAPHICLIB_VERSION_NUM(1,37,0)
30 ...
31 #endif
32 * \endcode
33 **********************************************************************/
34#define GEOGRAPHICLIB_VERSION \
35 GEOGRAPHICLIB_VERSION_NUM(GEOGRAPHICLIB_VERSION_MAJOR, \
36 GEOGRAPHICLIB_VERSION_MINOR, \
37 GEOGRAPHICLIB_VERSION_PATCH)
38
39// For reference, here is a table of Visual Studio and _MSC_VER
40// correspondences:
41//
42// _MSC_VER Visual Studio
43// 1900 vc14 (2015) First version of VS to include enough C++11 support
44// 191[0-6] vc15 (2017) First version of VS to include enough C++17 support
45// 192[0-9] vc16 (2019)
46// 1930-1944 vc17 (2022)
47// vc18 (2026)
48
49#if defined(_MSC_VER) && defined(GEOGRAPHICLIB_SHARED_LIB) && \
50 GEOGRAPHICLIB_SHARED_LIB
51# if GEOGRAPHICLIB_SHARED_LIB > 1
52# error GEOGRAPHICLIB_SHARED_LIB must be 0 or 1
53# elif defined(GeographicLib_SHARED_EXPORTS)
54# define GEOGRAPHICLIB_EXPORT __declspec(dllexport)
55# else
56# define GEOGRAPHICLIB_EXPORT __declspec(dllimport)
57# endif
58#else
59# define GEOGRAPHICLIB_EXPORT
60#endif
61
62#include <stdexcept>
63#include <string>
64#include <GeographicLib/Math.hpp>
65
66/**
67 * \brief Namespace for %GeographicLib
68 *
69 * All of %GeographicLib is defined within the GeographicLib namespace. In
70 * addition all the header files are included via GeographicLib/Class.hpp.
71 * This minimizes the likelihood of conflicts with other packages.
72 **********************************************************************/
73namespace GeographicLib {
74
75 /**
76 * \brief %Constants needed by %GeographicLib
77 *
78 * Define constants specifying the WGS84 ellipsoid, the UTM and UPS
79 * projections, and various unit conversions.
80 *
81 * Example of use:
82 * \include example-Constants.cpp
83 **********************************************************************/
84 class GEOGRAPHICLIB_EXPORT Constants {
85 private:
86 typedef Math::real real;
87 Constants() = delete; // Disable constructor
88
89 public:
90 /**
91 * A synonym for Math::degree<real>().
92 **********************************************************************/
93 static Math::real degree() { return Math::degree(); }
94 /**
95 * @return the number of radians in an arcminute.
96 **********************************************************************/
97 static Math::real arcminute()
98 { return Math::degree() / Math::dm; }
99 /**
100 * @return the number of radians in an arcsecond.
101 **********************************************************************/
102 static Math::real arcsecond()
103 { return Math::degree() / Math::ds; }
104
105 /** \name Ellipsoid parameters
106 **********************************************************************/
107 ///@{
108 /**
109 * @tparam T the type of the returned value.
110 * @return the equatorial radius of WGS84 ellipsoid (6378137 m).
111 **********************************************************************/
112 template<typename T = real> static T WGS84_a()
113 { return 6378137 * meter<T>(); }
114 /**
115 * @tparam T the type of the returned value.
116 * @return the flattening of WGS84 ellipsoid (1/298.257223563).
117 **********************************************************************/
118 template<typename T = real> static T WGS84_f() {
119 // Evaluating this as 1000000000 / T(298257223563LL) reduces the
120 // round-off error by about 10%. However, expressing the flattening as
121 // 1/298.257223563 is well ingrained.
122 return 1 / ( T(298257223563LL) / 1000000000 );
123 }
124 /**
125 * @tparam T the type of the returned value.
126 * @return the gravitational constant of the WGS84 ellipsoid, \e GM, in
127 * m<sup>3</sup> s<sup>&minus;2</sup>.
128 **********************************************************************/
129 template<typename T = real> static T WGS84_GM()
130 { return T(3986004) * 100000000 + 41800000; }
131 /**
132 * @tparam T the type of the returned value.
133 * @return the angular velocity of the WGS84 ellipsoid, &omega;, in rad
134 * s<sup>&minus;1</sup>.
135 **********************************************************************/
136 template<typename T = real> static T WGS84_omega()
137 { return 7292115 / (T(1000000) * 100000); }
138 /**
139 * @tparam T the type of the returned value.
140 * @return the equatorial radius of GRS80 ellipsoid, \e a, in m.
141 **********************************************************************/
142 template<typename T = real> static T GRS80_a()
143 { return 6378137 * meter<T>(); }
144 /**
145 * @tparam T the type of the returned value.
146 * @return the gravitational constant of the GRS80 ellipsoid, \e GM, in
147 * m<sup>3</sup> s<sup>&minus;2</sup>.
148 **********************************************************************/
149 template<typename T = real> static T GRS80_GM()
150 { return T(3986005) * 100000000; }
151 /**
152 * @tparam T the type of the returned value.
153 * @return the angular velocity of the GRS80 ellipsoid, &omega;, in rad
154 * s<sup>&minus;1</sup>.
155 *
156 * This is about 2 &pi; 366.25 / (365.25 &times; 24 &times; 3600) rad
157 * s<sup>&minus;1</sup>. 365.25 is the number of days in a Julian year and
158 * 365.35/366.25 converts from solar days to sidereal days. Using the
159 * number of days in a Gregorian year (365.2425) results in a worse
160 * approximation (because the Gregorian year includes the precession of the
161 * earth's axis).
162 **********************************************************************/
163 template<typename T = real> static T GRS80_omega()
164 { return 7292115 / (T(1000000) * 100000); }
165 /**
166 * @tparam T the type of the returned value.
167 * @return the dynamical form factor of the GRS80 ellipsoid,
168 * <i>J</i><sub>2</sub>.
169 **********************************************************************/
170 template<typename T = real> static T GRS80_J2()
171 { return T(108263) / 100000000; }
172 /**
173 * @tparam T the type of the returned value.
174 * @return the central scale factor for UTM (0.9996).
175 **********************************************************************/
176 template<typename T = real> static T UTM_k0()
177 {return T(9996) / 10000; }
178 /**
179 * @tparam T the type of the returned value.
180 * @return the central scale factor for UPS (0.994).
181 **********************************************************************/
182 template<typename T = real> static T UPS_k0()
183 { return T(994) / 1000; }
184 ///@}
185
186 /** \name Triaxial ellipsoid parameters
187 *
188 * These parameters are close to the values given by Milan Bursa, Vladimira
189 * Fialova, "Parameters of the Earth's tri-axial level ellipsoid", Studia
190 * Geophysica et Geodaetica 37(1), 1-13 (1993).
191 * - longitude of major axis = &minus;14.93&deg; &plusmn; 0.05&deg;
192 * - \e a = 6378171.36 m &plusmn; 0.30 m
193 * - \e a / (\e a &minus; \e c) = 297.7738 &plusmn; 0.0003
194 * - \e a / (\e a &minus; \e b) = 91449 &plusmn; 60
195 * .
196 * which gives: \e a = 6378171.36 m, \e b = 6378101.61 m, \e c = 6356751.84
197 * m. Here take the semiaxes to be whole numbers of meters, with (\e a +
198 * \e b)/2 = WGS84_a(), \e a &minus; \e b = 70 m, \e c = round(WGS84_a() *
199 * (1 - WGS84_f())). This gives
200 * - \e a = 6378172 m
201 * - \e b = 6378102 m
202 * - \e c = 6356752 m
203 * - \e lon0 = &minus;14.93&deg;
204 **********************************************************************/
205 ///@{
206 /**
207 * @tparam T the type of the returned value.
208 * @return the major semiaxis of a triaxial approximation to the Earth, \e
209 * a, in m (= 6378172).
210 **********************************************************************/
211 template<typename T = real> static T Triaxial_Earth_a()
212 { return WGS84_a<T>() + 70/real(2); }
213 /**
214 * @tparam T the type of the returned value.
215 * @return the median semiaxis of a triaxial approximation to the Earth, \e
216 * b, in m (= 6378102).
217 **********************************************************************/
218 template<typename T = real> static T Triaxial_Earth_b()
219 { return WGS84_a<T>() - 70/real(2); }
220 /**
221 * @tparam T the type of the returned value.
222 * @return the minor semiaxis of a triaxial approximation to the Earth, \e
223 * c, in m (= 6356752).
224 **********************************************************************/
225 template<typename T = real> static T Triaxial_Earth_c()
226 { using std::round; return round(WGS84_a<T>() * (1 - WGS84_f())); }
227 /**
228 * @tparam T the type of the returned value.
229 * @return the longitude, with respect to Greenwich, of the major semiaxis
230 * of of a triaxial approximation to the Earth, \e lon0, in degrees (=
231 * &minus;14.93).
232 **********************************************************************/
233 template<typename T = real> static T Triaxial_Earth_lon0()
234 { return T(1493) / 100; }
235 ///@}
236
237 /** \name SI units
238 **********************************************************************/
239 ///@{
240 /**
241 * @tparam T the type of the returned value.
242 * @return the number of meters in a meter.
243 *
244 * This is unity, but this lets the internal system of units be changed if
245 * necessary.
246 **********************************************************************/
247 template<typename T = real> static T meter() { return T(1); }
248 /**
249 * @return the number of meters in a kilometer.
250 **********************************************************************/
251 static Math::real kilometer()
252 { return 1000 * meter<real>(); }
253 /**
254 * @return the number of meters in a nautical mile (approximately 1 arc
255 * minute)
256 **********************************************************************/
257 static Math::real nauticalmile()
258 { return 1852 * meter<real>(); }
259
260 /**
261 * @tparam T the type of the returned value.
262 * @return the number of square meters in a square meter.
263 *
264 * This is unity, but this lets the internal system of units be changed if
265 * necessary.
266 **********************************************************************/
267 template<typename T = real> static T square_meter()
268 { return meter<T>() * meter<T>(); }
269 /**
270 * @return the number of square meters in a hectare.
271 **********************************************************************/
272 static Math::real hectare()
273 { return 10000 * square_meter<real>(); }
274 /**
275 * @return the number of square meters in a square kilometer.
276 **********************************************************************/
277 static Math::real square_kilometer()
278 { return kilometer() * kilometer(); }
279 /**
280 * @return the number of square meters in a square nautical mile.
281 **********************************************************************/
282 static Math::real square_nauticalmile()
283 { return nauticalmile() * nauticalmile(); }
284 ///@}
285
286 /** \name Anachronistic British units
287 **********************************************************************/
288 ///@{
289 /**
290 * @return the number of meters in an international foot.
291 **********************************************************************/
292 static Math::real foot()
293 { return real(254 * 12) / 10000 * meter<real>(); }
294 /**
295 * @return the number of meters in a yard.
296 **********************************************************************/
297 static Math::real yard() { return 3 * foot(); }
298 /**
299 * @return the number of meters in a fathom.
300 **********************************************************************/
301 static Math::real fathom() { return 2 * yard(); }
302 /**
303 * @return the number of meters in a chain.
304 **********************************************************************/
305 static Math::real chain() { return 22 * yard(); }
306 /**
307 * @return the number of meters in a furlong.
308 **********************************************************************/
309 static Math::real furlong() { return 10 * chain(); }
310 /**
311 * @return the number of meters in a statute mile.
312 **********************************************************************/
313 static Math::real mile() { return 8 * furlong(); }
314 /**
315 * @return the number of square meters in an acre.
316 **********************************************************************/
317 static Math::real acre() { return chain() * furlong(); }
318 /**
319 * @return the number of square meters in a square statute mile.
320 **********************************************************************/
321 static Math::real square_mile() { return mile() * mile(); }
322 ///@}
323
324 /** \name Anachronistic US units
325 **********************************************************************/
326 ///@{
327 /**
328 * @return the number of meters in a US survey foot.
329 **********************************************************************/
330 static Math::real surveyfoot()
331 { return real(1200) / 3937 * meter<real>(); }
332 ///@}
333 };
334
335 /**
336 * \brief Exception handling for %GeographicLib
337 *
338 * A class to handle exceptions. It's derived from std::runtime_error so it
339 * can be caught by the usual catch clauses.
340 *
341 * Example of use:
342 * \include example-GeographicErr.cpp
343 **********************************************************************/
344 class GeographicErr : public std::runtime_error {
345 public:
346
347 /**
348 * Constructor
349 *
350 * @param[in] msg a string message, which is accessible in the catch
351 * clause via what().
352 **********************************************************************/
353 GeographicErr(const std::string& msg) : std::runtime_error(msg) {}
354 };
355
356} // namespace GeographicLib
357
358#endif // GEOGRAPHICLIB_CONSTANTS_HPP
GEOGRAPHICLIB_EXPORT
#define GEOGRAPHICLIB_EXPORT
Definition Constants.hpp:59
real
GeographicLib::Math::real real
Definition Geod3Solve.cpp:25
Math.hpp
Header for GeographicLib::Math class.
GeographicLib::Constants::yard
static Math::real yard()
Definition Constants.hpp:297
GeographicLib::Constants::Triaxial_Earth_b
static T Triaxial_Earth_b()
Definition Constants.hpp:218
GeographicLib::Constants::arcsecond
static Math::real arcsecond()
Definition Constants.hpp:102
GeographicLib::Constants::Triaxial_Earth_a
static T Triaxial_Earth_a()
Definition Constants.hpp:211
GeographicLib::Constants::square_kilometer
static Math::real square_kilometer()
Definition Constants.hpp:277
GeographicLib::Constants::degree
static Math::real degree()
Definition Constants.hpp:93
GeographicLib::Constants::UPS_k0
static T UPS_k0()
Definition Constants.hpp:182
GeographicLib::Constants::mile
static Math::real mile()
Definition Constants.hpp:313
GeographicLib::Constants::hectare
static Math::real hectare()
Definition Constants.hpp:272
GeographicLib::Constants::kilometer
static Math::real kilometer()
Definition Constants.hpp:251
GeographicLib::Constants::fathom
static Math::real fathom()
Definition Constants.hpp:301
GeographicLib::Constants::GRS80_J2
static T GRS80_J2()
Definition Constants.hpp:170
GeographicLib::Constants::square_nauticalmile
static Math::real square_nauticalmile()
Definition Constants.hpp:282
GeographicLib::Constants::GRS80_GM
static T GRS80_GM()
Definition Constants.hpp:149
GeographicLib::Constants::surveyfoot
static Math::real surveyfoot()
Definition Constants.hpp:330
GeographicLib::Constants::furlong
static Math::real furlong()
Definition Constants.hpp:309
GeographicLib::Constants::arcminute
static Math::real arcminute()
Definition Constants.hpp:97
GeographicLib::Constants::WGS84_omega
static T WGS84_omega()
Definition Constants.hpp:136
GeographicLib::Constants::GRS80_a
static T GRS80_a()
Definition Constants.hpp:142
GeographicLib::Constants::GRS80_omega
static T GRS80_omega()
Definition Constants.hpp:163
GeographicLib::Constants::UTM_k0
static T UTM_k0()
Definition Constants.hpp:176
GeographicLib::Constants::square_mile
static Math::real square_mile()
Definition Constants.hpp:321
GeographicLib::Constants::square_meter
static T square_meter()
Definition Constants.hpp:267
GeographicLib::Constants::meter
static T meter()
Definition Constants.hpp:247
GeographicLib::Constants::chain
static Math::real chain()
Definition Constants.hpp:305
GeographicLib::Constants::foot
static Math::real foot()
Definition Constants.hpp:292
GeographicLib::Constants::WGS84_f
static T WGS84_f()
Definition Constants.hpp:118
GeographicLib::Constants::WGS84_a
static T WGS84_a()
Definition Constants.hpp:112
GeographicLib::Constants::acre
static Math::real acre()
Definition Constants.hpp:317
GeographicLib::Constants::Triaxial_Earth_c
static T Triaxial_Earth_c()
Definition Constants.hpp:225
GeographicLib::Constants::Triaxial_Earth_lon0
static T Triaxial_Earth_lon0()
Definition Constants.hpp:233
GeographicLib::Constants::WGS84_GM
static T WGS84_GM()
Definition Constants.hpp:129
GeographicLib::Constants::nauticalmile
static Math::real nauticalmile()
Definition Constants.hpp:257
GeographicLib::GeographicErr::GeographicErr
GeographicErr(const std::string &msg)
Definition Constants.hpp:353
GeographicLib::Math::degree
static T degree()
Definition Math.hpp:197
GeographicLib::Math::dm
static constexpr int dm
minutes per degree
Definition Math.hpp:143
GeographicLib::Math::ds
static constexpr int ds
seconds per degree
Definition Math.hpp:147
GeographicLib::Math::real
double real
Definition Math.hpp:115
GeographicLib
Namespace for GeographicLib.
Definition Accumulator.cpp:12
std
Definition NearestNeighbor.hpp:806