/**
* 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;
}
/**
* Calculates the Julian day of a date in the Julian calendar
*
* This algorithm is invalid for negative Julian days.
*
* @param int $year The year, for example: 2000, -1000, 0
* @param int $month The month, from 1 to 12
* @param float $day The day, from 1 to 31, or with decimals
* @return int|bool The Julian day, or false on error
*/
function aa_julian_date_to_julian_day($year, $month, $day)
{
if ($month <= 2) {
$year--;
$month += 12;
}
$julian_day = aa_int(365.25 * ($year + 4716)) + aa_int(30.6001 * ($month + 1)) + $day - 1524.5;
if ($julian_day < 0) {
aa_set_error('This algorithm is invalid for negative Julian days.');
return false;
}
return $julian_day;
}
/**
* Adds a number of days to a date
*
* The calendar in which the date falls is automatically detected.
* This algorithm is invalid for negative Julian days.
*
* @param int $year The year, for example: 2000, -1000, 0
* @param int $month The month, from 1 to 12
* @param float $day The day, from 1 to 31, or with decimals
* @param float $days_to_add The number of days to add, example: 1, 2, -1, -2, -1.25, 1.5
* @return array|bool The new year or false on error
* @returns int 0 The year
* @returns int 1 The month
* @returns float 2 The day
*/
function aa_add_days_to_date($year, $month, $day, $days_to_add)
{
$julian_day = aa_date_to_julian_day($year, $month, $day);
if ($julian_day === false) {
return false;
}
$julian_day += $days_to_add;
if ($julian_day < 0) {
aa_set_error('This algorithm is invalid for negative Julian days.');
return false;
}
$new_date = aa_julian_day_to_date($julian_day);
return $new_date;
}
/**
* Sets the Earth ellipsoid
*
* @param string $earth_ellipsoid The new Earth ellipsoid, default = WGS-1984
* @return string|bool False if the ellipsoid is invalid, the previous Earth ellipsoid otherwise
*/
function aa_set_earth_ellipsoid($earth_ellipsoid = null)
{
global $_aa_earth_ellipsoid;
global $_aa_earth_ellipsoids;
$previous_earth_ellipsoid = $_aa_earth_ellipsoid;
if (is_null($earth_ellipsoid)) {
$earth_ellipsoid = EARTH_ELLIPSOID;
} else {
if (!isset($_aa_earth_ellipsoids[$earth_ellipsoid])) {
aa_set_error('Invalid ellipsoid.');
return false;
}
}
$_aa_earth_ellipsoid = $earth_ellipsoid;
return $previous_earth_ellipsoid;
}
/**
* Returns the list of algorithms
*
* @param string $type The type of list: "algorithms", "categories", "both"
* @return array The list of the algorithms
*/
function aa_get_algorithms($type = null)
{
global $_aa_algorithms;
global $_aa_algorithm_categories;
global $_aa_algorithms_by_category;
is_null($type) and $type = 'algorithms';
switch ($type) {
case 'algorithms':
return $_aa_algorithms;
case 'categories':
return $_aa_algorithm_categories;
case 'both':
return $_aa_algorithms_by_category;
default:
aa_set_error('Type of list invalid.');
return false;
}
}
/**
* Calculates the date from a Julian day
*
* The calendar in which the date falls is automatically detected.
* This algorithm is invalid for negative Julian days.
*
* @param int $julian_day The Julian day
* @return array|bool The date or false on error
* @returns int 0 The year
* @returns int 1 The month
* @returns float 2 The day
*/
function aa_julian_day_to_date($julian_day)
{
if ($julian_day < 0) {
aa_set_error('This algorithm is invalid for negative Julian days.');
return false;
}
$julian_day += 0.5;
$Z = aa_int($julian_day);
$F = $julian_day - $Z;
// fixes Meeus original algorithm (p. 63) to calculate the Julian day of the change of calendar
// the value of 2299161 is the Julian day for 1582-10-15 in the Gregorian calendar + 0.5
// 1582-10-15 is the default first day of the Gregorian calendar
list($change_year, $change_month, $change_day) = aa_get_calendar_change_date();
$change_julian_day = aa_gregorian_date_to_julian_day($change_year, $change_month, $change_day);
$change_julian_day += 0.5;
if ($Z < $change_julian_day) {
$A = $Z;
} else {
$alpha = aa_int(($Z - 1867216.25) / 36524.25);
$A = $Z + 1 + $alpha - aa_int($alpha / 4);
}
$B = $A + 1524;
$C = aa_int(($B - 122.1) / 365.25);
$D = aa_int(365.25 * $C);
$E = aa_int(($B - $D) / 30.6001);
$day = $B - $D - aa_int(30.6001 * $E) + $F;
if ($E < 14) {
$month = $E - 1;
} else {
if ($E == 14 or $E == 15) {
$month = $E - 13;
} else {
aa_set_error('The calculated value of the month is out of range.');
return false;
}
}
if ($month > 2) {
$year = $C - 4716;
} else {
$year = $C - 4715;
}
return array($year, $month, $day);
}
/**
* Converts seconds of arc into a given format
*
* @param float $seconds The seconds of arc
* @param string $format The format: DEGREES, RADIANS, default = null or SECONDS (passthru)
* @return float|array The degrees expressed in the given format
*/
function aa_seconds_to_format($seconds, $format = null)
{
switch ($format) {
case 'DEGREES':
case 'degrees':
$degrees = $seconds / 3600;
break;
case 'RADIANS':
case 'radians':
$degrees = deg2rad($seconds / 3600);
break;
case 'SECONDS':
case 'seconds':
case null:
// passthru
$degrees = $seconds;
break;
default:
aa_set_error('Invalid format.');
return false;
}
return $degrees;
}
