Entity_and_Attribute_Overview:
Not all files contain the same HYPACK strings, but this list represents all the HYPACK strings represented in the files. These are the original files, no corrections have been made to these files.
The times recorded in the navigation file are in UTC. Keywords and the information they provide are as follows:
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 vessel name, agencies involved with the survey, and the location of the survey.
ELL: Ellipsoid information. The name of the ellipsoid followed by the semi-major axis in meters and the flattening ratio.
PRO: Project 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.
DEV 0: For survey 2015-001-FA: Indicates that lines collected with device designation 0 are lines of Differential Global Positioning System (DGPS) collected with the ProFlex*** DGPS receiver. ***Note: this is mislabeled in the header as Hemisphere DGPS.***
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. ***A change to the n3 offset occurred on JD 185 (file 001_1224.185) where the n3 offset for DEV 0 was changed from 0 to -4.2 and DEV 1 changed from -4.43 to -4.2. This change occurred after the GPS antenna offsets for DEV 0 and DEV 1 were remeasured and found to be both 4.2 m from the water line. This does not affect the data used for this survey.***
PRD: Private Device Data, which has multiple formats depending on the type of device generating the data. KTD for is example is a Kinematic Tide Datum File.
DDT: identifies the device that the computer clock is being synchronized to.
DEV 1: For survey 2015-001-FA: Indicates that lines collected with device designation 1 are lines of Differential Global Positioning System (DGPS) collected with the Hemisphere*** DGPS receiver. ***Note: this is mislabeled in the header as ProFlex DGPS.***
DEV 2: Disabled for survey 2015-001-FA.
DEV 3: Disabled for survey 2015-001-FA.
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 (0 for Proflex and 1 for Hemisphere DGPS) 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 18 N, 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.
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 2015-001-FA there were several different messages were sent from the GPS systems: $GPGGA, $GPVTG, and $GPRMC were standard throughout the survey. These message strings will be defined below.
TID: Tide correction in the format "TID dn t dc" where dn=device number, t=time tag (seconds past midnight), dc = draft correction. ***considered unusable for this survey.
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.
KTC: Describes how HYPACK records water levels (tide corrections) when using RTK where “KTC dn t nv eh lh u kval offset draft final” where dn = device number, t=time tag (seconds past midnight, matches GPS position), nv=number of values, eh= WGS84ellipsoidal height (from GPS), lh= local ellipsoidal height (on local ellipsoid), u=undulation, kval= K value, offset= antenna offset, draft=draft correction, final=final tide ***considered unusable for this survey.
The (National Marine Electronics Association) NMEA strings $GPGGA, $GPVTG, $GPRMC and $GPZDA are stored in the HYPACK file. These are defined as follows.
$GPGGA is GPS fix data in the format "$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 hemisphere; q=fix quality where 0=fix not available or invalid; 1=GPS fix; 2=Differential GPS fix; 3=GPS PPS Mode fix; 4=RTK fix; 5=RTK float; 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.
Example: $GPGGA,160209.00,3806.336689,N,07505.875090,W,4,11,0.9,5.038,M,-36.840,M,1,0378*61 UTC Time = 160209.00 Latitude = 3806.336689 N Longitude = 07505.875090 W Fix Quality = 4 (indicates RTK) Number of satellites = 11 HDOP = 0.9 relative accuracy of horizontal position Altitude = 5.038 meters above mean sea level Height of geoid above WGS84 ellipsoid = -36.840 meters Time since last update = 01 Checksum = *61.
$GPVTG is track made good and ground speed in the format "$GPVTG, true, T, mag, M, grsp1, N, grsp2, K, mode", where t=true course made good over ground in degrees, T= True, m=magnetic course made good over ground in degrees, M=magnetic, grsp1=ground speed, N=Knots, grsp2=ground speed, K=Kilometers per hour, mode=Mode indicator (A=Autonomous, D=Differential, E=Estimated, N=Data not valid).
Example: $GPVTG,340.39,T,356.37,M,005.50,N,010.18,K,D*27 True course made good: 340.39 Magnetic course made good: 356.37 Ground speed (knots) = 5.5 Ground speed (kilometers) = 10.18 Mode=Differential
$GPRMC is the recommended minimum specific GPS/TRANSIT data in the format "$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.
Example: $GPRMC,210134.00,A,3748.21357,N,07520.67408,W,4.66,201.72,130715,,,D*48 UTC time = 210134.00 Navigation receiver warning = A Latitude 37 deg. 48.21357 min North Longitude 075 deg. 20.67408 min West Speed over ground = 4.66 (kts) Course Made Good = 201.72 (deg True) Date of fix = 130715 (DDMMYY) mandatory checksum = D*48
$GPZDA is UTC Date/Time and Local Time Zone Offset in the format "$GPZDA,hhmmss.ss,xx,xx,xxxx,xx,xx" where hhmmss.ss=UTC, xx=Day, 01 to 31, xx=month, 01 to 12, xxx=Year, xx=Local zone description, 00 to +/- 13 hours, xx=Local zone minutes description (same sign as hours), checksum.
Example: $GPZDA,173357.00,28,04,2007,,*69 UTC= 173357.00 UTC day = 28 UTC month = 04 UTM year = 2007 Local zone hours = null Local zone minutes = null Checksum = *69
Entity_and_Attribute_Detail_Citation:
