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

#                    S V E L _ C O R R E C T I O N S . P L 

#                    doc: Thu Dec 30 01:35:18 2010

#                    dlm: Tue May 24 16:44:07 2016

#                    (c) 2010 A.M. Thurnherr

#                    uE-Info: 116 64 NIL 0 0 72 0 2 4 NIL ofnI

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

# HISTORY:

#	Dec 30, 2010: - created

#	Oct  5, 2011: - sscorr_w temporarily disabled

#				  - re-enabled

#	Oct 26, 2011: - BUG? in calc_binDepth() on very shallow station 38 in

#					2010 Gom Spill data set the uplooker code did not stop

#				 	at the surface, requiring additon of another test

#	Mar  4, 2014: - added support for missing TILT (PITCH/ROLL)

#	May 12, 2016: - removed unused lines of code

#	May 18, 2016: - removed assumption of 1500m/s soundspeed setting

#				  - made sscorr_w return nan on undef'd input vel

#   May 24, 2016: - calc_binDepths() -> binDepths()

#				  - added caching to binDepths

# NOTES:

#	In an effort to track down the scale bias, NBP0901 stn 160 was reprocessed with various

#   simplified soundspeed correction methods:

#		1) no sscorr: bias is depth dependent and disappears btw 2500 and 3000m

#		2) simplified (dBin/dADCP): very similar to full correction, esp. when dBin is used

#		3) hacked correction (1450m/s vs 1500m/s assumed soundspeed) => bias largely disappears

sub sscorr_w($$$$$)												# sound-speed correction for w

{																# see RDI Coord. Trans. manual sec. 4.1, ...

	my($wObs,$wCTD,$ssADCP,$dADCP,$dBin) = @_;					# but there is an error: the ^2 applies to the []

	return nan unless numberp($wObs);

	my($tanSqBeamAngle) = tan(rad($LADCP{BEAM_ANGLE}))**2;

	$dADCP = int($dADCP);										# @sVelProf is binned to 1m

	$dBin = int($dBin);

	while (!numberp($sVelProf[$dADCP])) { $dADCP--; }			# skip gaps & bottom of profile

	while (!numberp($sVelProf[$dBin ])) { $dBin--;  }

	my($Kn) = sqrt(1 + (1 - $sVelProf[$dBin]/$sVelProf[$dADCP])**2 * $tanSqBeamAngle);

	return ($wObs*$sVelProf[$dBin]/$ssADCP - $wCTD) / $Kn;		# full correction

}

sub binDepths($)												# see RDI Coord Trans manual sec. 4.2

{

	my($ens) = @_;

	return @{$LADCP{ENSEMBLE}[$ens]->{BIN_DEPTHS}}				# cached result

		if (@{$LADCP{ENSEMBLE}[$ens]->{BIN_DEPTHS}});

	my(@bindz);													# if not cached => calculate

	# if the following assertion fails, the entire code needs to be searched for

	# each call of calc_binDepths() needs to be protected by a test

	die("ensemble $ens") unless defined($LADCP{ENSEMBLE}[$ens]->{TILT});

	my($tanSqBeamAngle) = tan(rad($LADCP{BEAM_ANGLE}))**2;

	my($curdz) = 0;												# calc avg sndspeed btw transducer & 1st bin

	$curdz-- until numberp($sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)]);

	my($avgss) = my($ADCPss) = $sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)];

	my($sumss) = my($nss) = 0;

	if ($LADCP{ENSEMBLE}[$ens]->{XDUCER_FACING_UP}) {

		while ($curdz >= -$LADCP{DISTANCE_TO_BIN1_CENTER}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT}))) {

			if (numberp($sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)])) {

				$sumss += $sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)]; $nss++;

			}

			$curdz--;

		}

	} else {

		while ($curdz <= $LADCP{DISTANCE_TO_BIN1_CENTER}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT}))) {

			if (numberp($sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)])) {

				$sumss += $sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)]; $nss++;

			}

			$curdz++;

		}

	}

	$avgss = $sumss/$nss if ($nss>0);

	my($Kn) = sqrt(1 + (1 - $avgss/$ADCPss)**2 * $tanSqBeamAngle);

	$bindz[0] = $LADCP{ENSEMBLE}[$ens]->{XDUCER_FACING_UP} ?

					- $LADCP{DISTANCE_TO_BIN1_CENTER}*$Kn*$avgss/$LADCP{ENSEMBLE}[$ens]->{SPEED_OF_SOUND}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT})) :

					+ $LADCP{DISTANCE_TO_BIN1_CENTER}*$Kn*$avgss/$LADCP{ENSEMBLE}[$ens]->{SPEED_OF_SOUND}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT}));

	for (my($bin)=1; $bin<=$LADCP_lastBin-1; $bin++) {

		$sumss = $nss = 0;

		if ($LADCP{ENSEMBLE}[$ens]->{XDUCER_FACING_UP}) {

			while ($curdz >= $bindz[$bin-1]-$LADCP{BIN_LENGTH}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT}))) {

				last unless (int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz) >= 0);

				if (numberp($sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)])) {

					$sumss += $sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)]; $nss++;

				}

				$curdz--;

			}

		} else {

			while ($curdz <= $bindz[$bin-1]+$LADCP{BIN_LENGTH}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT}))) {

				if (numberp($sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)])) {

					$sumss += $sVelProf[int($LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH}+$curdz)]; $nss++;

				}

				$curdz++;

			}

		}

		$avgss = $sumss/$nss if ($nss > 0);			# otherwise, leave avgss as is

		$Kn = sqrt(1 + (1 - $avgss/$ADCPss)**2 * $tanSqBeamAngle);

		$bindz[$bin] = $LADCP{ENSEMBLE}[$ens]->{XDUCER_FACING_UP} ?

						$bindz[$bin-1] - $LADCP{BIN_LENGTH}*$Kn*$avgss/$LADCP{ENSEMBLE}[$ens]->{SPEED_OF_SOUND}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT})) :

	                    $bindz[$bin-1] + $LADCP{BIN_LENGTH}*$Kn*$avgss/$LADCP{ENSEMBLE}[$ens]->{SPEED_OF_SOUND}*cos(rad($LADCP{ENSEMBLE}[$ens]->{TILT}));

    }

    for (my($i)=0; $i<@bindz; $i++) {							# cache result

    	$LADCP{ENSEMBLE}[$ens]->{BIN_DEPTHS}[$i] = $LADCP{ENSEMBLE}[$ens]->{CTD_DEPTH} + $bindz[$i];

    }

	return @{$LADCP{ENSEMBLE}[$ens]->{BIN_DEPTHS}};				# return result

}

1;