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This commit is contained in:
Timur A. Fatkhullin
2025-03-21 13:08:23 +03:00
parent c0cba8422f
commit 441743ff01
5 changed files with 114 additions and 42 deletions
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108
cxx/mount_astrom.h
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@@ -14,6 +14,12 @@
#include "mount_astrom_default.h"
#include "utils.h"
namespace erfa
{
#include <erfa.h>
#include <erfam.h>
} // namespace erfa
namespace mcc::traits
{
@@ -36,6 +42,14 @@ concept mcc_real_or_char_range =
namespace mcc::astrom
{
// a time duration represented in radians (the precision is near 1 nanosecond)
// typedef std::chrono::duration<double, std::ratio<134670467, 10000000000000000>> mcc_radsec_duration_t;
typedef std::chrono::duration<double, std::ratio<134670467, 10000000000000000>> mcc_chrono_radians;
// https://gssc.esa.int/navipedia/index.php?title=CEP_to_ITRF
static constexpr double mcc_UT1_to_sideral_ratio = 1.002737909350795; // UT1/sideral
// modified Julian date (based on ERFA eraCal2jd)
template <traits::mcc_real_scalar_or_real_range_c ResT>
@@ -132,24 +146,34 @@ static int mcc_julday(const std::chrono::system_clock::time_point& start_time,
/*
* angles are in degrees or sexagimal string form
* RA and DEC are apparent!
*
* returns
* NaN if object is non-rising or "alt_limit" < 0, Inf is circumpolar
*/
template <traits::mcc_real_or_char_range AT,
traits::mcc_real_or_char_range RT,
traits::mcc_real_or_char_range DT,
traits::mcc_real_or_char_range LT>
double mcc_time_to_alt_limit(const AT& alt_limit,
const RT& RA,
const DT& DEC,
const LT& LAT,
const std::chrono::system_clock::time_point& now)
double mcc_time_to_alt_limit(traits::mcc_real_or_char_range auto const& alt_limit,
traits::mcc_real_or_char_range auto const& RA,
traits::mcc_real_or_char_range auto const& DEC,
traits::mcc_real_or_char_range auto const& LAT,
traits::mcc_real_or_char_range auto const& LON,
const std::chrono::system_clock::time_point& now,
traits::mcc_time_duration_c auto const& dut1, // UT1-UTC
traits::mcc_time_duration_c auto const& tt_tai, // TT-TAI
// TAI-UTC (leap seconds)
traits::mcc_time_duration_c auto const& tai_utc)
{
// sin(alt) = sin(DEC)*sin(phi) + cos(DEC)*cos(phi)*cos(HA)
// HA = LST - RA
// cos(HA) = cos(LST)*cos(RA) + sin(LST)*sin(RA)
double ra, dec, lat, alt;
using AT = std::decay_t<decltype(alt_limit)>;
using RT = std::decay_t<decltype(RA)>;
using DT = std::decay_t<decltype(DEC)>;
using LT = std::decay_t<decltype(LAT)>;
using LGT = std::decay_t<decltype(LON)>;
double ra, dec, lat, lon, alt;
if constexpr (std::floating_point<AT>) {
alt = alt_limit * utils::deg2radCoeff;
@@ -183,25 +207,53 @@ double mcc_time_to_alt_limit(const AT& alt_limit,
lat *= utils::deg2radCoeff;
}
if constexpr (std::floating_point<LGT>) {
lon = LON * utils::deg2radCoeff;
} else {
lon = utils::parsAngleString(LON);
lon *= utils::deg2radCoeff;
}
if (lat >= 0.0) { // north hemisphere
if (dec < (lat - std::numbers::pi / 2.0)) { // never rises above horizont
if (dec < (lat - std::numbers::pi / 2.0)) { // never rises above horizon
return std::numeric_limits<double>::quiet_NaN();
}
} else { // south hemisphere
if (dec > (lat + std::numbers::pi / 2.0)) { // never rises above horizont
if (dec > (lat + std::numbers::pi / 2.0)) { // never rises above horizon
return std::numeric_limits<double>::quiet_NaN();
}
}
double cos_ha = (std::sin(alt) - std::sin(dec) * std::sin(lat)) / std::cos(dec) / std::cos(lat);
if (std::abs(cos_ha) > 1.0) { // circumpolar (it never sets below horizon)
if (std::abs(cos_ha) > 1.0) { // it never sets below given altitude
return std::numeric_limits<double>::infinity();
}
double lst = std::acos(cos_ha) + ra;
auto ut1 = now + dut1;
auto tt = now + tai_utc + tt_tai;
return 0.0;
double ut1_mjd, tt_mjd, result;
int ret = mcc_julday(ut1, ut1_mjd);
if (ret) {
return std::numeric_limits<double>::quiet_NaN();
}
ret = mcc_julday(tt, tt_mjd);
if (ret) {
return std::numeric_limits<double>::quiet_NaN();
}
double lst_now = erfa::eraGst06a(ERFA_DJM0, ut1_mjd, ERFA_DJM0, tt_mjd) + lon;
result = lst - lst_now;
if (result < 0.0) { // the next sideral day
result += 2.0 * std::numbers::pi;
}
result *= mcc_UT1_to_sideral_ratio; // to UT1 scale
return result;
}
@@ -218,6 +270,7 @@ class MccLeapSeconds final
{
public:
typedef std::chrono::system_clock::time_point time_point_t;
typedef std::chrono::duration<double> real_secs_t; // seconds duration in double
MccLeapSeconds()
{
@@ -308,7 +361,8 @@ public:
}
std::optional<double> operator[](const time_point_t& tp) const
// std::optional<double> operator[](const time_point_t& tp) const
std::optional<real_secs_t> operator[](const time_point_t& tp) const
{
if (tp > _expireDate) { // ???????!!!!!!!!!!!
return std::nullopt;
@@ -319,14 +373,16 @@ public:
for (auto const& el : _db | std::views::reverse) {
if (ymd >= el.ymd) {
return el.tai_utc;
// return el.tai_utc;
return real_secs_t{el.tai_utc};
}
}
return std::nullopt;
}
std::optional<double> operator[](const double& mjd) const
// std::optional<double> operator[](const double& mjd) const
std::optional<real_secs_t> operator[](const double& mjd) const
{
double e_mjd;
@@ -338,7 +394,7 @@ public:
for (auto const& el : _db | std::views::reverse) {
if (mjd >= el.mjd) {
return el.tai_utc;
return real_secs_t{el.tai_utc};
}
}
@@ -379,6 +435,7 @@ class MccIersBulletinA final
{
public:
typedef std::chrono::system_clock::time_point time_point_t;
typedef std::chrono::duration<double> real_secs_t; // seconds duration in double
struct pole_pos_t {
double x, y;
@@ -421,13 +478,15 @@ public:
}
double TT_TAI() const
// double TT_TAI() const
real_secs_t TT_TAI() const
{
return _tt_tai;
return real_secs_t{_tt_tai};
}
// DUT1 = UT1 - UTC
std::optional<double> DUT1(const time_point_t& tp) const
// std::optional<double> DUT1(const time_point_t& tp) const
std::optional<real_secs_t> DUT1(const time_point_t& tp) const
{
// use of the closest date
std::chrono::year_month_day ymd{std::chrono::round<std::chrono::days>(tp)};
@@ -443,14 +502,15 @@ public:
auto el_prev = _db.front();
for (auto const& el : _db) {
if (ymd <= el.ymd) {
return el.dut1;
return real_secs_t{el.dut1};
}
}
return std::nullopt;
}
std::optional<double> DUT1(double mjd) const
// std::optional<double> DUT1(double mjd) const
std::optional<real_secs_t> DUT1(double mjd) const
{
mjd = std::round(mjd); // round to closest integer MJD
@@ -464,7 +524,7 @@ public:
for (auto const& el : _db) {
if (mjd <= el.mjd) {
return el.dut1;
return real_secs_t{el.dut1};
}
}