/**
* Converts decimal degrees into a given format
*
* @param float $degrees The decimal degrees
* @param string $format The format: DMS, HMS, MOD360, NONE, RADIANS, default = NONE
* @param bool $mod360 True to convert degrees to a value between 0 and 360 degrees before formating,
* false otherwise, default = false
* @return float|array The degrees expressed in the given format
* @returns int 0 The degrees or the hours
* @returns int 1 The minutes
* @returns float 2 The seconds
* @returns bool 3 True if positive, false if negative
*/
function aa_degrees_to_format($degrees, $format = null, $mod360 = false)
{
if ($mod360) {
$degrees = aa_degrees_to_mod360($degrees);
}
switch ($format) {
case 'DMS':
case 'dms':
$degrees = aa_degrees_to_dms($degrees);
break;
case 'HMS':
case 'hms':
$degrees = aa_degrees_to_hms($degrees);
break;
case 'MOD360':
case 'mod360':
$degrees = aa_degrees_to_mod360($degrees);
break;
case 'NONE':
case null:
// passthru, no formatting
break;
case 'RADIANS':
case 'radians':
$degrees = deg2rad($degrees);
break;
default:
aa_set_error('Invalid format.');
return false;
}
return $degrees;
}
/**
* Converts decimal degrees into hours, minutes and seconds
*
* @param float $degrees The decimal degrees
* @return array The degrees expressed in hours, minutes and seconds
* @returns int 0 The hours
* @returns int 1 The minutes
* @returns float 2 The seconds
*/
function aa_degrees_to_hms($degrees)
{
$degrees = aa_degrees_to_mod360($degrees);
$time = $degrees * 24 / 360;
$hours = (int) $time;
$remainder = ($time - $hours) * 60;
$minutes = (int) $remainder;
$seconds = ($remainder - $minutes) * 60;
return array($hours, $minutes, $seconds);
}
/**
* Calculates the nutation arguments
*
* This function is used internally to calculate the nutation.
*
* @param int $time The time measured in Julian centuries from the Epoch J2000.0 (JDE 2451 545.0)
* @param bool $use_cache Caches the arguments of the nutation during the calculation, default = true
* @return float The nutation arguments
*/
function aa_nutation_arguments($time, $use_cache = true)
{
global $_aa_nutation_periodic_terms;
static $cache = array();
if ($use_cache === false or !isset($cache[$time])) {
$T2 = $time * $time;
$T3 = $T2 * $time;
$D = aa_degrees_to_mod360(297.85036 + 445267.11148 * $time - 0.0019142 * $T2 + $T3 / 189474);
$M = aa_degrees_to_mod360(357.52772 + 35999.05034 * $time - 0.0001603 * $T2 - $T3 / 300000);
$Mprime = aa_degrees_to_mod360(134.96298 + 477198.867398 * $time + 0.0086972 * $T2 + $T3 / 56250);
$F = aa_degrees_to_mod360(93.27191000000001 + 483202.017538 * $time - 0.0036825 * $T2 + $T3 / 327270);
$omega = aa_degrees_to_mod360(125.04452 - 1934.136261 * $time + 0.0020708 * $T2 + $T3 / 450000);
foreach ($_aa_nutation_periodic_terms as $terms) {
list($coef_D, $coef_M, $coef_Mprime, $coef_F, $coef_omega, $coef0_sin, $coef1_sin) = $terms;
$nutation_arguments[] = deg2rad($coef_D * $D + $coef_M * $M + $coef_Mprime * $Mprime + $coef_F * $F + $coef_omega * $omega);
}
if ($use_cache === false) {
return $nutation_arguments;
}
$cache[$time] = $nutation_arguments;
}
return $cache[$time];
}
function calculate_first_argument($time)
{
$T2 = $time * $time;
$T3 = $T2 * $time;
return deg2rad(aa_degrees_to_mod360(125.04452 - 1934.136261 * $time + 0.0020708 * $T2 + $T3 / 450000));
}
