#======================================================================

#                    L I B T I D E S . P L 

#                    doc: Thu Aug 24 21:37:14 2006

#                    dlm: Thu Apr 26 10:22:53 2012

#                    (c) 2006 A.M. Thurnherr

#                    uE-Info: 17 0 NIL 0 0 72 2 2 4 NIL ofnI

#======================================================================

# tidal calculations

# HISTORY:

#   Aug 24, 2006: - created during GRAVILUCK

#   Jan 22, 2008: - renamed M2() to M2_bias()

#                 - added M2_phase()

#   Apr 26, 2012: - added K1 & M2 tidal frequencies

#----------------------------------------------------------------------

# tidal frequencies

#   - taken from thesis Makefile

#   - according to my memory, the values are from Apel's book

#----------------------------------------------------------------------

$M2 = 24/1.9322;

$K1 = 24/1.0027;

#----------------------------------------------------------------------

# given t0, a decimal day at the beginning of "flood", return a scale

# between -1 and 1 that can be multiplied with the max tidal flow amplitude

# to estimate tidal velocity at time t. 

#----------------------------------------------------------------------

sub M2_bias(@)

{

	my($t0,$t) = &antsFunUsage(2,'ff','time-origin, time',@_);

	return sin(2*3.14159265358979 * ($t-$t0) / ($M2/24));

}

sub M2_phase(@)

{

	my($t0,$t) = &antsFunUsage(2,'ff','time-origin, time',@_);

	return round(360 * frac(($t-$t0) / ($M2/24)));

}

1;