LSSTApplications  19.0.0-11-g2ce9f25+2,20.0.0+1,20.0.0+11,20.0.0+2,20.0.0+3,20.0.0+4,20.0.0+5,20.0.0+8,20.0.0+9,20.0.0-1-g009f3de,20.0.0-1-g10df615+8,20.0.0-1-g253301a+4,20.0.0-1-g32a200e+8,20.0.0-1-g596936a+9,20.0.0-1-g8a53f90+1,20.0.0-1-gc96f8cb+10,20.0.0-1-gd1c87d7+1,20.0.0-15-g34741e2+3,20.0.0-2-g04cfba9+2,20.0.0-2-gec03fae+2,20.0.0-3-g082faa5+1,20.0.0-3-g2fa8bb8+6,20.0.0-3-gbdbfa727+1,20.0.0-4-gde602ef96+3,20.0.0-4-ge48a6ca+4,20.0.0-8-g1acaa36,20.0.0-8-g7eef53f7+5,w.2020.27
LSSTDataManagementBasePackage
constants.h
Go to the documentation of this file.
1 /*
2  * LSST Data Management System
3  * Copyright 2014-2015 AURA/LSST.
4  *
5  * This product includes software developed by the
6  * LSST Project (http://www.lsst.org/).
7  *
8  * This program is free software: you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation, either version 3 of the License, or
11  * (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16  * GNU General Public License for more details.
17  *
18  * You should have received a copy of the LSST License Statement and
19  * the GNU General Public License along with this program. If not,
20  * see <https://www.lsstcorp.org/LegalNotices/>.
21  */
22 
23 #ifndef LSST_SPHGEOM_CONSTANTS_H_
24 #define LSST_SPHGEOM_CONSTANTS_H_
25 
28 
29 
30 namespace lsst {
31 namespace sphgeom {
32 
33 // Note: given a compiler that does correctly rounded decimal to
34 // binary floating point conversions, PI = 0x1.921fb54442d18p1 in
35 // IEEE double precision format. This is less than π.
36 constexpr double PI = 3.1415926535897932384626433832795;
37 constexpr double ONE_OVER_PI = 0.318309886183790671537767526745;
38 constexpr double RAD_PER_DEG = 0.0174532925199432957692369076849;
39 constexpr double DEG_PER_RAD = 57.2957795130823208767981548141;
40 
41 // The maximum error of std::asin in IEEE double precision arithmetic,
42 // assuming 1 ulp of error in its argument, is about
43 // π/2 - arcsin (1 - 2⁻⁵³), or a little less than 1.5e-8 radians
44 // (3.1 milliarcsec).
45 constexpr double MAX_ASIN_ERROR = 1.5e-8;
46 
47 // The computation of squared chord length between two unit vectors
48 // involves 8 elementary operations on numbers with magnitude ≤ 4. Its
49 // maximum error can be shown to be < 2.5e-15.
50 constexpr double MAX_SQUARED_CHORD_LENGTH_ERROR = 2.5e-15;
51 
52 // The largest value ε such that 1 + ε rounds to 1 in IEEE double
53 // precision, assuming round-to-nearest-ties-to-even rounding.
54 constexpr double EPSILON = 1.1102230246251565e-16;
55 
56 }} // namespace lsst::sphgeom
57 
58 #endif // LSST_SPHGEOM_CONSTANTS_H_
lsst::sphgeom::PI
constexpr double PI
Definition: constants.h:36
lsst::sphgeom::RAD_PER_DEG
constexpr double RAD_PER_DEG
Definition: constants.h:38
lsst::sphgeom::ONE_OVER_PI
constexpr double ONE_OVER_PI
Definition: constants.h:37
lsst::sphgeom::MAX_SQUARED_CHORD_LENGTH_ERROR
constexpr double MAX_SQUARED_CHORD_LENGTH_ERROR
Definition: constants.h:50
lsst
A base class for image defects.
Definition: imageAlgorithm.dox:1
lsst::sphgeom::DEG_PER_RAD
constexpr double DEG_PER_RAD
Definition: constants.h:39
lsst::sphgeom::MAX_ASIN_ERROR
constexpr double MAX_ASIN_ERROR
Definition: constants.h:45
lsst::sphgeom::EPSILON
constexpr double EPSILON
Definition: constants.h:54