lsst.sphgeom g0261d94427+c9b10be330
constants.h
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22
23#ifndef LSST_SPHGEOM_CONSTANTS_H_
24#define LSST_SPHGEOM_CONSTANTS_H_
25
28
29
30namespace lsst {
31namespace 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.
36constexpr double PI = 3.1415926535897932384626433832795;
37constexpr double ONE_OVER_PI = 0.318309886183790671537767526745;
38constexpr double RAD_PER_DEG = 0.0174532925199432957692369076849;
39constexpr 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).
45constexpr 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.
50constexpr 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.
54constexpr double EPSILON = 1.1102230246251565e-16;
55
56}} // namespace lsst::sphgeom
57
58#endif // LSST_SPHGEOM_CONSTANTS_H_