HYPACK RAW File Header Information. Interpretation:
Posted by Christian Shaw on 25 September 2015 09:48 AM
HYPACK RAW File Header Information. Interpretation:
FTP: The first record located at the top of the header used to identify the file format.
VER: HYPACK version number
INF: General survey information filled in by the data technician. This typically contains the survey participants, the vessel name, other agencies involved with the survey, and the location of the survey.
FIL: Raw format file.
ELL: Ellipsoid information. The name of the ellipsoid followed by the semi-major axis in meters and the flattening ration.
PRO: Projection information record where TME indicates Transverse Mercator and the central meridian of -75 indicates UTM, zone 18.
DTM: Datum transformation record
GEO: Geoid model. Blank if not present.
HVU: Horizontal and Vertical Units (meters)
TND: Survey time and date in UTC.
OFF: Device Offsets in the format "OFF dn n1 n2 n3 n4 n5 n6 n7" where dn = device number; n1 = starboard or port offset (positive starboard); n2 = forward or aft offset (positive forward); n3 = height (antenna) or depth (transducer draft) offset; n4 = yaw rotation angle (positive for clockwise rotation); n5 = roll rotation angle (port side up is positive); n6 = pitch rotation angle (bow up is positive); n7 = device latency in seconds.
DEV 0: First Driver in HYPACK Hardware List.
DEV 1: Second Driver in HYPACK Hardware List. Dev 2 etc... to follow.
DDT: Place holder for a custom device driver of a "SMI" (Special Marine Instrument)).
LIN 2: planned line data follows
PTS: planned line waypoints (easting and northing, UTM, zone 18N, meters)
LBP: planned line begin point (easting and northing, UTM zone 18N, meters)
LNN: planned line name
EOL: end of planned line
USR: user information
EOH: end of header.
The remaining elements have similar information in the first 3 columns. The first column will indicate the data type, the second column will indicate the device that recorded the information and the third column is the time tag (seconds past midnight) that is also sometimes referred to as the latency. The remaining information on each line is specific to the data type. Not all data types were recorded in each HYPACK file.
POS: Position of the ship in the format "POS dn t x y" where dn=device number; t=time tag (seconds past midnight); x=easting; y=northing. On this cruise these values are in UTM, Zone 19, WGS84.
QUA: Position quality information in the format "QUA dn t n m h sat mode" where dn=device number; t=time tag (seconds past midnight); n=number of values to follow; m = 10 minus HDOP (horizontal dilution of precision); h=HDOP; sat=number of satellites; mode=GPS mode (NMEA 0183 standard values) where 0 = fix not available or invalid; 1 = GPS fix; 2 = Differential GPS fix; 3 = GPS PPS Mode fix; 4 = RTK fix; and 5 = RTK Float. The last 3 values are decoded from GST message: standard deviation of latitude error (meters); standard deviation of longitude error (meters); Standard deviation of semi-major axis of error ellipsis (meters).
RAW: Position information in the format "RAW dn t n lat long alt utc" where dn=device number; t=time tag (seconds past midnight); n=number of values to follow; lat=raw latitude in the format ddmmmm.mmmm. To convert to ddmm.mmmmm multiply by 100; long=raw longitude in the format ddmmmm.mmmm. To convert to ddmm.mmmmm multiply by 100; alt=antenna altitude above ellipsoid (meters); utc=GPS time in the format HHMM.
CAP: Information captured by the HYPACK system sent from an external device in the format "CAP dn t val" where dn=device number; t=time tag (seconds past midnight); val=value passed by the instrument. In this case the value being passed is a pressure depth value in the units of PSI. For example: *000126.9844 = 26.9844 PSI (disregard the *0001). One would need to subtract atmospheric pressure (1 atm ~= 14.7 psi_ from this value to obtain the sensor PSI reading.
MSG: Message string in the format "MSG dn t message" where dn=device number; t=time tag (seconds past midnight); message is the message sent from the device. During survey 2012-005-FA there were several different messages were sent from the GPS systems: $GPGGA, $GPVTG, $GPRMC, and $GPZDA were standard throughout the survey. These message strings will be defined below.
GYR: Gyro data (heading) in the format "GYR dn t h" where dn=device number, t=time tag (seconds past midnight), h=heading.
FIX: events marked manually by the user in the format "FIX dn t event_number" where dn=device number (typically 99 as there is no device for manual events); t=time tag (seconds past midnight); event_number=event number such as 1,2,3,4.
MSG strings from GPS:
$GPGGA is GPS fix data in the format "$GPGGA, t, lat, lath, long, longh, q, sat, h, a, M, alt, M, t2, refcheck" where t=time in UTC in the format hhmmss.ss; lat=latitude in the format ddmm.mmmmmm; lath= N or S indicating the latitude hemisphere; long=longitude in the format dddmm.mmmmmm; longh=E or W indicating the longitude hemisphere; q=fix quality where 2 is a DGPS fix; sat=number of satellites; h=Horizontal Dilution of Precision (HDOP); a=Antenna altitude above mean sea level (geoid); M= units of antenna altitude in meters; alt=height of geoid above WGS84 ellipsoid; M=units of geoidal height in meters; t2=time since last DGPS update; refcheck=DGPS reference station id and the checksum.
$GPRMC is the recommended minimum specific GPS/TRANSIT data in the format "$GPRMC, hhmmss.ss, A, llll.ll, a, yyyyy.yy, a,x.x, x.x, ddmmyy, x.x, a, m*hh" where hhmmss.ss=UTC time fix, A=data staus (A=valid position, V=navigation receiver warning), llll.ll=latitude in the format ddmm.mmm, a=North/South, yyyyy.yy=longitude in the format dddmm.mmm, a=East/West, x.x=speed over ground in knots, x.x=track angle in degrees true, ddmmyy=UTC date of fix, x.x=magnetic variation degrees (Easterly variation subtracts from true course), a= E or W of magnetic varation, m= mode indicate (A=autonomous, D=Differential, E=Estimate, N=Data not valid), *hh=checksum.
$GPVTG is track made good and ground speed in the format "$GPVTG, t, T, m, M, n, N, k, K refcheck" where t=true course made good over ground, degrees; T indicates the previous number refers to true course; m=magnetic course made good over ground, dgrees; M indicates the previous number refers to magnetic course; n=ground speed; N indicates the previous number refers to Knots, k=ground speed; K indicates the previous number refers to Kilometers per hour, refcheck= checksum at the end of the string with the first character an *.
$GPZDA is UTC Date/Time and local time zone offset in the format "$GPZDA, hhmmss.ss,dd,mm,yyyy, xx, yy checksum" where hhmmss.ss= time in UTC; dd=UTC day; mm=UTC month; yyyy=UTC year; xx=offset to local time zone in hours; yy=offset to local time zone in minutes;checksum ***on this cruise the navigation computer was set to UTC time so the $GPZDA string indicates zero time offset.
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