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

#                    doc: Sat Jan 18 14:54:43 2003

#                    (c) 2003 A.M. Thurnherr

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

# HISTORY:

#	Jan 18, 2003: - incepted aboard the Aurora Australis (KAOS)

#	Jan 19, 2003: - continued

#	Jan 20, 2003: - replaced INTENSITY by AMPLITUDE

#	Jan 21, 2003: - changed heading-correction field names

#	Jan 27, 2003: - cosmetics

#	Feb 14, 2003: - moved BT setup into header

#	Mar 15, 2003: - moved 10th xmit voltage into header as BATTERY field

#				  - removed again, because values are not meaningful

#	Feb 24, 2004: - continued aboard Nathaniel B. Palmer (Anslope II)

#				  - BUG: ensemble # was wrong on error messages

#	Feb 26, 2004: - removed ESW_ERROR and bitmasking of ERROR_STATUS_WORD

#	Feb 27, 2004: - removed some unused (commented-out) baggage

#	Mar 11, 2004: - BUG: renamed ACD -> ADC

#	Mar 18, 2004: - cosmetics

#	Mar 30, 2004: - rewrote to speed up reading; new version takes

#					~40% less time

#	Sep 14, 2005: - made BT data optional (NUMBER_OF_DATA_TYPES)

#				  - added DATA_FORMAT

#	Sep 15, 2005: - debugged

#				  - implement checksum to robustly find EOF

#				  - renamed to RDI_BB_Read.pl

#				  - BUG: had used POSIX::mktime with wrong month def!

#	Oct 30, 2005: - added WH300 FW16.27 file format

#				  - added DATA_FORMAT_VARIANT

#				  - changed semantics so that first valid ensemble is

#				    in E[0] (instead of E[$ensNo-1])

#	Nov  8, 2005: - replaced UNIXTIME by UNIX_TIME

#				  - added SECNO

#	Aug 31: 2006: - added DAYNO

#	Aug  1, 2007: - BUG: typo in monthLength()

#	Sep 18, 2007: - modified readHeader() readDta() WBRhdr() WBRens() to

#					conserve memory (no large arrays as retvals)

#	Jun  4, 2008: - BUG: BB150 code was not considered on Sep 18, 2007

#	Aug 15, 2010: - downgraded "unexpected number of data types" from error to warning

#				  - BUG: WBRcfn had not been set correctly

#				  - modified to allow processing files without time info

#	May 12, 2011: - added code to report built-in-test errors

#	Mar 19, 2013: - added support for WH600 data file (58 fixed leader bytes)

#	Mar 20, 2013: - removed DATA_FORMAT stuff

#				  - added support for BT data in subset of ensembles

#	Apr 29, 2013: - changed semantics to assume EOF when unexpected number of data types

#					are present in an ensemble

#	Nov 25, 2013: - renamed from [RDI_BB_Read.pl]

#				  - begin implementing WBWens()

#				  - checkEnsemble() expunged

#	Mar  3, 2014: - BUG: WBPens() did not handle incomple ensembles at EOF correctly

#	Mar  4, 2014: - added support for DATA_SOURCE_ID

#	Apr 24, 2014: - added debug statements to log %-GOOD values

#	May  6, 2014: - loosened input format checks

#	May  7, 2014: - removed BT_present flag

#	Sep  6, 2014: - adapted WBRhdr to >7 data types

#	Oct 15, 2014: - implemented work-around for readData() not recognizing

#					incomplete ensemble at the end, which seems to imply that there is

#				    a garbage final ensemble that passes the checksum test???

#	Oct  2, 2015: - added &skip_initial_trash()

#	Dec 18, 2015: - added most data types to WBPofs()

#				  - BUG: WBPens() requires round() for scaled values

#	Jan  9, 2016: - removed system() from writeData()

#				  - BUG: WBRhdr() did not set DATA_SOURCE_ID

#				  - added PRODUCER

#				  - BUG: writeData() did not work correctly for ECOGIG OC26 moored data (spaces in filename?)

#				  - added support for patching coordinate system

#	Feb 16, 2016: - added transducer orientation to WBPens()

#				  - BUG: most WBPens() error messages used wrong file name

#	Feb 23, 2016: - changed WBRhdr() to use 2nd ensemble (with correct data-source id)

#	Feb 26, 2016: - added basic BT data to WBPens(); not BT_RL_* and BT_SIGNAL_STRENGTH

#	Feb 29, 2016: - LEAP DAY: actually got BT data patching to work

#	Jul 30, 2016: - BUG: incomplete last ensemble with garbage content was returned on reading

#						 WH300 data

# FIRMWARE VERSIONS:

#	It appears that different firmware versions generate different file

#	structures. Currently (Sep 2005) these routines have been tested

#	with the following firmware versions (as reported by [listHdr]):

#

#	Firmw.	DATA_FORMAT(_VARIANT)	Owner 	Cruise	FIXED_LEADER_LENGTH

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

#	05.52	BB150 (1)				UH 		CLIVAR/P16S 42

#	16.12	WH300 (1)				FSU 	A0304		53

#	16.21	WH300 (1)				LDEO 	NBP0402		53

#	16.27	WH300 (2)				Nash 	?			59

# PD0 FILE FORMAT EXTENSIONS:

#

#	- file creator encoded in DATA_SOURCE_ID

#

#	- first ensemble uses default RDI DATA_SOURCE_ID because the LDEO_IX

#	  software assumes this

#

#	- DATA_SOURCE_ID = 0x7F						original TRDI PD0 file

#

#	- DATA_SOURCE_ID = 0xA0 | PATCHED_MASK		produced by IMP+LADP 

#		PATCHED_MASK & 0x04:						pitch value has been patched

#		PATCHED_MASK & 0x02:						roll value has been patched

#		PATCHED_MASK & 0x01:						heading value has been patched

#			- PITCH & ROLL can be missing (0x8000 badval as in velocities)

#			- HEADING can be missing (0xF000 badval, as 0x8000 is valid 327.68 heading)

#

#	- DATA_SOURCE_ID = 0xE0 					produced by editPD0

# NOTES:

#	- RDI stores data in VAX/Intel byte order (little endian)

#	- the output data structure does not exactly mirror the file data

#	  structure; the header is not stored at all and the fixed leader

#	  data are not duplicated in every ensemble

#	- in the RDI files some fields that logically belong into the header

#	  or the fixed leader (e.g. BT_MIN_CORRELATION) appear in the 

#	  ensemble data --- these are not read on input

#	- the field names are generally unabbreviated except for

#	  BT (= Bottom Track), RL (= Reference Layer), MIN and MAX

#	- all arrays are 0-referenced, but the ensemble number is not!

#	- a list of filenames can be be passed to readData() so that

#	  files split onto several memory cards (typically .000 .001 &c)

#	  can be read --- not sure if this works, actually

#	- the RDI manuals are not entirely clear everywhere; I have made

#	  guesses in some cases, but they should not affect the main

#	  fields of interest

#	- some fields in the fixed leader are not really fixed in a LADCP

#	  setting (e.g. xducer orientation); I'v made an educated guess

#	  as to which fields to move to the ENS array

#	- all units except pressure are SI, i.e. in m and m/s

#	- I don't understand the ERROR_STATUS_WORD; here's what 3 different

#	  instruments returned:

#	  	0x88000100	FSU instrument during A0304 (Firmware 16.12)

#		0x88008180	LDEO uplooker (slave) during NBP0402 (Firmware 16.21)

#		0x00008180	LDEO downlooker (master) during NBP0402 (Firmware 16.21)

#	  According to the manual (January 2001 version) this would, for example,

#	  indicate power failures on both FSU and LDEO slave instruments...

# &readData() returns perl obj (ref to anonymous hash) with the following

# structure:

#

#	DATA_SOURCE_ID					scalar		0x7f (Workhorse, also DVL)

#	NUMBER_OF_DATA_TYPES			scalar		6 (no BT) or 7

#	ENSEMBLE_BYTES					scalar		?, number of bytes w/o checksum

#	HEADER_BYTES					scalar		?

#	FIXED_LEADER_BYTES				scalar		42 for BB150; 53 for WH300, 58 for WH600, 59 for WH300(Nash)

#	VARIABLE_LEADER_BYTES			scalar		?

#	VELOCITY_DATA_BYTES				scalar		?

#	CORRELATION_DATA_BYTES			scalar		?

#	ECHO_INTENSITY_DATA_BYTES		scalar		?

#	PERCENT_GOOD_DATA_BYTES			scalar		?

#	BT_PRESENT						bool		NUMBER_OF_DATA_TYPES == 7

#	BT_DATA_BYTES					scalar		undefined, ? if BT_PRESENT

#	CPU_FW_VER						scalar		0--255

#	CPU_FW_REV						scalar		0--255

#	BEAM_FREQUENCY					scalar		75, 150, 300, 600, 1200, 2400 [kHz]

#	CONVEX_BEAM_PATTERN				bool		undefined, 1

#	CONCAVE_BEAM_PATTERN			bool		undefined, 1

#	SENSOR_CONFIG					scalar		1--3

#	XDUCER_HEAD_ATTACHED			bool		undefined, 1

#	BEAM_ANGLE						scalar		15,20,30,undefined=other [deg]

#	N_BEAMS							scalar		4--5

#	N_DEMODS						scalar		2--3(???),undefined=n/a

#	N_BINS							scalar		1--128

#	PINGS_PER_ENSEMBLE				scalar		0--16384

#	BIN_LENGTH						scalar		0.01--64 [m]

#	BLANKING_DISTANCE				scalar		0-99.99 [m]

#	MIN_CORRELATION					scalar		0--255

#	N_CODE_REPETITIONS				scalar		0--255

#	MIN_PERCENT_GOOD				scalar		1--100 [%]

#	MAX_ERROR_VELOCITY				scalar		0--5 [m/s]

#	TIME_BETWEEN_PINGS				scalar		0--? [s]

#	BEAM_COORDINATES				bool		undefined,1

#	INSTRUMENT_COORDINATES			bool		undefined,1

#	SHIP_COORDINATES				bool		undefined,1

#	EARTH_COORDINATES				bool		undefined,1

#	PITCH_AND_ROLL_USED				bool		undefined,1

#	USE_3_BEAM_ON_LOW_CORR			bool		undefined,1

#	BIN_MAPPING_ALLOWED				bool		undefined,1

#	HEADING_ALIGNMENT 				scalar		-179.99..180 [deg]

#	HEADING_BIAS			 		scalar		-179.99..180 [deg]

#	CALCULATE_SPEED_OF_SOUND		bool		undefined,1

#	USE_PRESSURE_SENSOR				bool		undefined,1

#	USE_COMPASS						bool		undefined,1

#	USE_PITCH_SENSOR				bool		undefined,1

#	USE_ROLL_SENSOR					bool		undefined,1

#	USE_CONDUCTIVITY_SENSOR			bool		undefined,1

#	USE_TEMPERATURE_SENSOR			bool		undefined,1

#	SPEED_OF_SOUND_CALCULATED		bool		undefined,1

#	PRESSURE_SENSOR_AVAILABLE		bool		undefined,1

#	COMPASS_AVAILABLE				bool		undefined,1

#	PITCH_SENSOR_AVAILABLE			bool		undefined,1

#	ROLL_SENSOR_AVAILABLE			bool		undefined,1

#	CONDUCTIVITY_SENSOR_AVAILABLE	bool		undefined,1

#	TEMPERATURE_SENSOR_AVAILABLE	bool		undefined,1

#	DISTANCE_TO_BIN1_CENTER			scalar		0--655.35 [m]

#	TRANSMITTED_PULSE_LENGTH		scalar		0--655.35 [m]

#	RL_FIRST_BIN					scalar		1--128

#	RL_LAST_BIN						scalar		1--128

#	FALSE_TARGET_THRESHOLD			scalar		0--254, undefined=disabled

#	LOW_LATENCY_SETTING				scalar		0--5(???)

#	TRANSMIT_LAG_DISTANCE			scalar		0--655.35 [m]

#	CPU_SERIAL_NUMBER				scalar		undefined, 0--65535 if WH300

#	NARROW_BANDWIDTH				bool		undefined,1 (only set if WH300)

#	WIDE_BANDWIDTH					bool		undefined,1 (only set if WH300)

#	TRANSMIT_POWER					scalar		undefined, 0--255(high) if WH300

#	TRANSMIT_POWER_HIGH				bool		undefined,1 (only set if WH300)

#	BT_PINGS_PER_ENSEMBLE			scalar		0--999

#	BT_DELAY_BEFORE_REACQUIRE		scalar		0--999

#	BT_MIN_CORRELATION				scalar		0--255

#	BT_MIN_EVAL_AMPLITUDE			scalar		0--255

#	BT_MIN_PERCENT_GOOD				scalar		0--100 [%]

#	BT_MODE							scalar		4,5,6(?)

#	BT_MAX_ERROR_VELOCITY			scalar		0--5 [m/s], undef=not screened

#	BT_RL_MIN_SIZE					scalar		0--99.9 [m]

#	BT_RL_NEAR						scalar		0--999.9 [m]

#	BT_RL_FAR						scalar		0--999.9 [m]

#	BT_MAX_TRACKING_DEPTH			scalar		8--999.9 [m]

#	ENSEMBLE[ensemble_no-1]			array		ensemble info

#		XDUCER_FACING_UP			bool		undefined, 1

#		XDUCER_FACING_DOWN			bool		undefined, 1

#		N_BEAMS_USED				scalar		3,4,5(?)

#		NUMBER						scalar		1--16777215

#		BUILT_IN_TEST_ERROR			scalar		?,undefined=none

#		SPEED_OF_SOUND				scalar		1400--1600 [m/s]

#		XDUCER_DEPTH				scalar		0.1--999.9 [m]

#		HEADING						scalar		0--359.99 [deg]    --- IMP EXTENSION: undef

#		PITCH						scalar		-20.00-20.00 [deg] --- IMP EXTENSION: undef

#		ROLL						scalar		-20.00-20.00 [deg] --- IMP EXTENSION: undef

#		SALINITY					scalar		0-40 [psu]

#		TEMPERATURE					scalar		-5.00--40.00 [deg]

#		MIN_PRE_PING_WAIT_TIME		scalar		? [s]

#		HEADING_STDDEV				scalar		0-180 [deg]

#		PITCH_STDDEV				scalar		0.0-20.0 [deg]

#		ROLL_STDDEV					scalar		0.0-20.0 [deg]

#		ADC_XMIT_CURRENT			scalar		0--255

#		ADC_XMIT_VOLTAGE			scalar		0--255

#		ADC_AMBIENT_TEMPERATURE		scalar		0--255

#		ADC_PRESSURE_PLUS			scalar		0--255

#		ADC_PRESSURE_MINUS			scalar		0--255

#		ADC_ATTITUDE_TEMPERATURE	scalar		0--255

#		ADC_ATTITUDE				scalar		0--255

#		ADC_CONTAMINATION			scalar		0--255

#		ERROR_STATUS_WORD			scalar		undefined, ? (only set if WH300)

#		PRESSURE					scalar		undefined, ?-? [dbar] (only set if WH300)

#		PRESSURE_STDDEV				scalar		undefined, ?-? [dbar] (only set if WH300)

#		DATE						string		MM/DD/YYYY

#		YEAR						scalar		?

#		MONTH						scalar		1--12

#		DAY							scalar		1--31

#		TIME						string		HH:MM:SS.hh

#		HOUR						scalar		0--23

#		MINUTE						scalar		0--59

#		SECONDS						scalar		0--59.99

#		UNIX_TIME					scalar		0--?

#		SECNO						scalar		0--? (number of seconds since daystart)

#		DAYNO						double		fractional day number since start of current year (1.0 is midnight Jan 1st)

#		VELOCITY[bin][beam]			scalars		-32.767--32.768 [m/s], undef=bad

#		CORRELATION[bin][beam]		scalars		1--255, undefined=bad

#		ECHO_AMPLITUDE[bin][beam]	scalars		0--255

#		PERCENT_GOOD[bin][beam]		scalars		0--255

#		BT_RANGE[beam]				scalars		tons [m]

#		BT_VELOCITY[beam]			scalars		see VELOCITY

#		BT_CORRELATION[beam]		scalars		see CORRELATION

#		BT_EVAL_AMPLITUDE[beam]		scalars		0--255

#		BT_PERCENT_GOOD[beam]		scalars		see PERCENT_GOOD

#		BT_RL_VELOCITY[beam]		scalars		see VELOCITY

#		BT_RL_CORRELATION[beam]		scalars		see CORRELATION

#		BT_RL_ECHO_AMPLITUDE[beam]	scalars		see ECHO_AMPLITUDE

#		BT_RL_PERCENT_GOOD[beam]	scalars		see PERCENT_GOOD

#		BT_SIGNAL_STRENGTH[beam]	scalars		0--255

#		HIGH_GAIN					bool		1, undefined

#		LOW_GAIN					bool		1, undefined

use strict;

use Time::Local;						# timegm()

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

# Time Conversion Subroutines

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

sub monthLength($$)										# of days in month

{

    my($Y,$M) = @_;

    return 31 if ($M==1 || $M==3 || $M==5 || $M==7 ||

                  $M==8 || $M==10 || $M==12);

    return 30 if ($M==4 || $M==6 || $M==9 || $M==11);

    return 28 if ($Y%4 != 0);

    return 29 if ($Y%100 != 0);

    return 28 if ($Y%400 > 0);

    return 29;

}

{ my($epoch,$lM,$lD,$lY,$ldn);							# static scope

  sub dayNo($$$$$$)

  {

	  my($Y,$M,$D,$h,$m,$s) = @_;

	  my($dn);

	  if ($Y==$lY && $M==$lM && $D==$lD) {				# same day as last samp

		  $dn = $ldn;

	  } else {											# new day

		  $epoch = $Y unless defined($epoch);			# 1st call

		  $lY = $Y; $lM = $M; $lD = $D;					# store

		  for ($dn=0,my($cY)=$epoch; $cY<$Y; $cY++) {	# multiple years

			  $dn += 337 + &monthLength($Y,$M);

		  }

		  $dn += $D;									# day in month

		  while (--$M > 0) {							# preceding months

			  $dn += &monthLength($Y,$M);

		  }

		  $ldn = $dn;									# store

	  }

	  return $dn + $h/24 + $m/24/60 + $s/24/3600;

  }

} # static scope

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

# Read Data

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

my($WBRcfn,$WBPcfn);									# current file names for reading/patching

my($BIT_errors) = 0;									# built-in-test errors

my($FmtErr) = "%s: illegal %s Id 0x%04x at ensemble %d";

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

# skip to first valid ensemble (skip over initial garbage)

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

sub skip_initial_trash(@)

{

	my($quiet) = @_;

	my($buf,$dta);

	my($found) = 0;										# zero consecutive 0x7f found

	my($skipped) = 0;

	while ($found < 2) {

		sysread(WBRF,$buf,1) == 1 || last;

		($dta) = unpack('C',$buf);

		if ($dta == 0x7f) {

			$found++;

		} elsif ($found==1 && ($dta==0xE0 || ($dta&0xF0==0xA0 && $dta&0x0F<8))) {

			$found++;

		} elsif ($found == 0) {

			$skipped++;

		} else {

			$skipped += $found;

			$found = 0;

		}

	}

	die("$WBRcfn: no valid ensemble header found [$!]\n")

		if ($found < 2);

	printf(STDERR "WARNING: %d bytes of initial garbage\n",$skipped)

		if ($skipped > 0 && !$quiet);

	return sysseek(WBRF,-2,1);

}

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

# readHeader(file_name,^dta) WBRhdr(^data)

#	- read header data

#	- also includes some data from 1st ens

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

sub readHeader(@)

{

	my($fn,$dta) = @_;

	$WBRcfn = $fn;

    open(WBRF,$WBRcfn) || die("$WBRcfn: $!");

}

sub WBRhdr($)

{

	my($dta) = @_;

	my($start_ens,$buf,$hid,$did,$Ndt,$B,$W,$i,$dummy,$id,@WBRofs);

	my($B1,$B2,$B3,$B4,$B5,$B6,$B7,$W1,$W2,$W3,$W4,$W5);

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

	# HEADER

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

	skip_initial_trash();

	($hid,$did,$dta->{ENSEMBLE_BYTES},$dummy,$dta->{NUMBER_OF_DATA_TYPES})

		= unpack('CCvCC',$buf);

	$hid == 0x7f || die(sprintf($FmtErr,$WBRcfn,"Header (hid)",$hid,0));

	$did == 0x7f || die(sprintf($FmtErr,$WBRcfn,"Header (did)",$did,0));

	($hid,$did,$dta->{ENSEMBLE_BYTES},$dummy,$dta->{NUMBER_OF_DATA_TYPES})

		= unpack('CCvCC',$buf);

	$hid == 0x7f || die(sprintf($FmtErr,$WBRcfn,"Header (hid2)",$hid,0));

	$dta->{DATA_SOURCE_ID} = $did;

	if ($did == 0x7f) {

		$dta->{PRODUCER} = 'TRDI ADCP';

	} elsif (($did&0xF0) == 0xA0) {

		$dta->{PRODUCER} = 'IMP+LADCP (Thurnherr software)';

	} elsif (($did&0xF0) == 0xE0) {

		$dta->{PRODUCER} = 'editPD0 (Thurnherr software)';

	} else {

		$dta->{PRODUCER} = sprintf('unknown (0x%02X)');

	}

	printf(STDERR "WARNING: unexpected number of data types (%d)\n",

		$dta->{NUMBER_OF_DATA_TYPES})

			unless ($dta->{NUMBER_OF_DATA_TYPES} == 6 ||

					$dta->{NUMBER_OF_DATA_TYPES} == 7);

##	$dta->{BT_PRESENT} = ($dta->{NUMBER_OF_DATA_TYPES} == 7);

	$dta->{BT_PRESENT} = ($dta->{NUMBER_OF_DATA_TYPES} >= 7);

	sysread(WBRF,$buf,2*$dta->{NUMBER_OF_DATA_TYPES})

		== 2*$dta->{NUMBER_OF_DATA_TYPES}

			|| die("$WBRcfn: $!");

	@WBRofs = unpack("v$dta->{NUMBER_OF_DATA_TYPES}",$buf);

	$dta->{HEADER_BYTES} 					= $WBRofs[0];

	$dta->{FIXED_LEADER_BYTES} 				= $WBRofs[1] - $WBRofs[0];

	$dta->{VARIABLE_LEADER_BYTES}			= $WBRofs[2] - $WBRofs[1];

	$dta->{VELOCITY_DATA_BYTES}				= $WBRofs[3] - $WBRofs[2];

	$dta->{CORRELATION_DATA_BYTES}			= $WBRofs[4] - $WBRofs[3];

	$dta->{ECHO_INTENSITY_DATA_BYTES}		= $WBRofs[5] - $WBRofs[4];

	if ($dta->{BT_PRESENT}) {

		$dta->{PERCENT_GOOD_DATA_BYTES}		= $WBRofs[6] - $WBRofs[5];

		$dta->{BT_DATA_BYTES}				= $dta->{ENSEMBLE_BYTES} - 4 - $WBRofs[6];

	} else {

		$dta->{PERCENT_GOOD_DATA_BYTES}		= $dta->{ENSEMBLE_BYTES} - 4 - $WBRofs[5];

	}

	if ($dta->{FIXED_LEADER_BYTES} == 42) {				# Eric Firing's old instrument I used in 2004

		$dta->{INSTRUMENT_TYPE} = 'BB150';

	} elsif ($dta->{FIXED_LEADER_BYTES} == 53) {		# old firmware: no serial numbers

		$dta->{INSTRUMENT_TYPE} = 'Workhorse';	

	} elsif ($dta->{FIXED_LEADER_BYTES} == 59) {		# new firmware: with serial numbers

		$dta->{INSTRUMENT_TYPE} = 'Workhorse';

    } elsif ($dta->{FIXED_LEADER_BYTES} == 58) {		# DVL

		$dta->{INSTRUMENT_TYPE} = 'Explorer';

    } 

#	for ($i=0; $i<$dta->{NUMBER_OF_DATA_TYPES}; $i++) {

#		printf(STDERR "\nWBRofs[$i] = %d",$WBRofs[$i]);

#	}

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

	# Check Data Format of 1st Ensemble

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

	sysseek(WBRF,$start_ens+$WBRofs[1],0) || die("$WBRcfn: $!");

	sysread(WBRF,$buf,2) == 2 || die("$WBRcfn: $!");

	$id = unpack('v',$buf);

	$id == 0x0080 || printf(STDERR $FmtErr."\n",$WBRcfn,"Variable Leader",$id,1);

	sysseek(WBRF,$start_ens+$WBRofs[2],0) || die("$WBRcfn: $!");

	sysread(WBRF,$buf,2) == 2 || die("$WBRcfn: $!");

	$id = unpack('v',$buf);

	$id == 0x0100 || printf(STDERR $FmtErr."\n",$WBRcfn,"Velocity Data",$id,1);

	sysseek(WBRF,$start_ens+$WBRofs[3],0) || die("$WBRcfn: $!");

	sysread(WBRF,$buf,2) == 2 || die("$WBRcfn: $!");

	$id = unpack('v',$buf);

	$id == 0x0200 || printf(STDERR $FmtErr."\n",$WBRcfn,"Correlation Data",$id,1);

	sysseek(WBRF,$start_ens+$WBRofs[4],0) || die("$WBRcfn: $!");

	sysread(WBRF,$buf,2) == 2 || die("$WBRcfn: $!");

	$id = unpack('v',$buf);

	$id == 0x0300 || printf(STDERR $FmtErr."\n",$WBRcfn,"Echo Intensity",$id,1);

	sysseek(WBRF,$start_ens+$WBRofs[5],0) || die("$WBRcfn: $!");

	sysread(WBRF,$buf,2) == 2 || die("$WBRcfn: $!");

	$id = unpack('v',$buf);

	$id == 0x0400 || printf(STDERR $FmtErr."\n",$WBRcfn,"Percent-Good Data",$id,1);

	my($BT_dt);

	if ($dta->{BT_PRESENT}) {

		for ($BT_dt=6; $BT_dt<$dta->{NUMBER_OF_DATA_TYPES}; $BT_dt++) {										# scan until BT found

			sysseek(WBRF,$start_ens+$WBRofs[$BT_dt],0) || die("$WBRcfn: $!");

			sysread(WBRF,$buf,2) == 2 || die("$WBRcfn: $!");

			$id = unpack('v',$buf);

			last if ($id == 0x0600);

		}

		if ($BT_dt == $dta->{NUMBER_OF_DATA_TYPES}) {

			printf(STDERR "WARNING: no BT data found\n");die;

			undef($dta->{BT_PRESENT});

		}

    }

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

	# FIXED LEADER

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

	sysseek(WBRF,$start_ens+$WBRofs[0],0) || die("$WBRcfn: $!");

	sysread(WBRF,$buf,42) == 42 || die("$WBRcfn: $!");

	($id,$dta->{CPU_FW_VER},$dta->{CPU_FW_REV},$B1,$B2,$dummy,$dummy,$dummy,

	 $dta->{N_BINS},$dta->{PINGS_PER_ENSEMBLE},$dta->{BIN_LENGTH},

	 $dta->{BLANKING_DISTANCE},$dummy,$dta->{MIN_CORRELATION},

	 $dta->{N_CODE_REPETITIONS},$dta->{MIN_PERCENT_GOOD},

	 $dta->{MAX_ERROR_VELOCITY},$dta->{TIME_BETWEEN_PINGS},$B3,$B4,$B5,

	 $dta->{HEADING_ALIGNMENT},$dta->{HEADING_BIAS},$B6,$B7,