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.
ELL: Ellipsoid information. The name of the ellipsoid followed by the semi-major axis in meters and the flattening ration.
PRO: Project information record where TME indicates Transverse Mercator and the central meridian of -69 indicates UTM, zone 19.
DTM: Datum transformation record.
GEO: Geoid Model File. Blank if not present. GEO <geo_file> <h_corr> where 'h_corr' is orthometric height correction in meters.
HVU: Horizontal and Vertical Units (meters)
TND: Survey time and date in UTC.
DEV 0: Lines with device designation 0 are lines of DGPS data.
OFF 0: device offsets for device 0. Format of the value is OFF dn n1 n2 n3 n4 n5 n6 n7 where dn=device number; n1=starboard, port offsets where positive is starboard; n2=forward, aft offset where positive is forward; n3=height (antenna) or depth (transducer draft) offset - always positive; n4=yaw rotation angle where positive for clockwise rotation; n5=roll rotation angle where port side up is positive; n6=pitch rotation angle where bow up is positive; n7=device latency in seconds. No offset for device 0 during this data collection.
DEV 1: Disabled.
DEV 2: Disabled.
DEV 3: Indicates that the lines with device designation 3 are lines of bathy data.
OFF 3: Offset of bathy data (transducer located 0.6 m below water line of vessel).
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.
POS: Position of the ship - in this case the antenna location - 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.
EC1: Echo Sounding (single frequency) in the format "EC1 dn t rd" where dn=device number; t=time tag (seconds past midnight); rd=raw depth.
GYR: Gyro Data (heading) in the format "GYR dn t h" where dn=device number; t=time tag (seconds past midnight); h=ship heading angle.
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. On this cruise, four different messages were sent from the DGPS: $GPVTG, $GPZDA, $SDDPT, and $GPGGA. These will be defined later.
FIX: Event marked manually by the user in the format "FIX dn t event number where dn=device number; t=time tag (seconds past midnight); event number=event number (1,2,3...) automatically increments. The device number is automatically supplying a value of 99.
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 2=Differential GPS fix. The next 3 values are the standard deviation of latitude error (meters), longitude error (meters) and semi-major axis of error ellipsis (meters).
The NMEA strings present in the HYPACK file are the $GPVTG, $GPZDA, $SDDPT, and $GPGGA. These sentences are defined as follows.
$GPVTG is track made good and ground speed in the format "$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.
$GPGGA is GPS fix data in the format "$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.
$SDDPT is water depth relative to the transducer. Field 1 is the depth in meters. Field 2 is the offset from the transducer: positive - distance from transducer to water line, or negative - distance from transducer to keel. Field 3 (asterisk and subsequent numbers and characters) is the CRC checksum of the NMEA data.
The purpose of these data is to provide the navigation for USGS cruise 2011-006-FA as recorded by CSI LGBX Pro Differential Global Positioning System (DGPS) with HYPACK software. This provides an archive of the original navigation as well as allowing others to reprocess the navigation for their purposes.
Are there legal restrictions on access or use of the data?
Use_Constraints:The public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
Neither the U.S. government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
|Data format:||This WinZip file contains the ANSI text HYPACK navigation files as well as the associated metadata files. in format WinZip (version 9.0) Size: 12.2|
|Media you can order:||DVD (Density 4.7 Gbytes) (format UDF)|
The user must have software capable of uncompressing the WinZip file.