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Minerals Management Service

U.S. Geological Survey Data Series 370

Navigation Data and Maps


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Raw Shotpoint Navigation

As the seismic reflection data were acquired, the position of the vessel was recorded using GPS and LOng RAnge Navigation (LORAN)-C systems; a description of the navigation acquistion system (1,445-KB PDF) has been provided in the RAW sub-folder located within the NAVIGATION folder. The accuracy of the LORAN-C varied from 528 to 1320 ft, with repeatable accuracy between 60 and 300 ft (http://www.navcen.uscg.gov/loran/handbook/h-book.htm.)

Positions were recorded in latitude and longitude coordinates every 5 min and appear on the seismic profiles as incremental, hand-annotated vertical event marks. Navigation data were obtained as DAT files, opened using Notepad, and saved as tab-deliminated text files with 9 columns:

Field 1: $LCGGA [denotes GPS receiver]
Field 2: HRMINS (UTC)
Field 3: LAT (Latitude, Degrees Minutes.m)
Field 4: N (North)
Field 5: LONG (Longitude, Degrees Minutes.m)
Field 6: W (West)
Field 7: Valid fix #1
Field 8: Valid fix #2
Field 9: Horizontal dilution of position

The outputs from the LORAN-C receiver consisted of five fields separated by commas and defined as follows:

Field 1: $LCGLL [denotes LORAN-C receiver]
Field 2: LAT (Latitude, Degrees Minutes.m)
Field 3: N (North)
Field 4: LONG (Longitude, Degrees Minutes.m)
Field 5: W (West)

92ER2 Annotated Navigation Fixes (1,540-KB PDF)

92ER4 Annotated Navigation Fixes (1,163-KB PDF)


Processed Shotpoint Navigation

Raw shotpoint navigation data were formatted for use with ESRI ArcGIS 9.2 software and projected in WGS84 to visually inspect shotpoint accuracy. Point locations were checked against written notes made on the paper records and in the cruise logbooks. Any errors were identified, reviewed, and rectified. Hour and minute values were not altered from the format in the original data files. Attribute information was updated to include the USGS-Woods Hole field activity ID and the new USGS-St. Petersburg MASH cruise ID, and to identify if the survey had been continuous or split into legs. Each processed Microsoft Excel navigation file contained 13 fields separated into columns and defined as follows:

Field 1: DATE (Month, Calendar Day, Year)
Field 2: D (DOY, Day of Year)
Field 3: H (Hour)
Field 4: M (Minute)
Field 5: LAT (Latitude, Decimal Degrees)
Field 6: LONG (Longitude, Decimal Degrees)
Field 7: CRUISE (USGS-St. Petersburg MASH Cruise ID)
Field 8: FIELD_ACT (USGS-Woods Hole Field Activity Number)
Field 9: METHOD (Data Collection Device)
Field 10: LEG (Cruise Leg)
Field 11: LINE (Trackline Number or Name)
Field 12: SHOT (Annotated Shot Number)
Field 13: LINE_SEG (Trackline Segment Name)

92ER2 Processed Shotpoint Navigation (112-KB Excel file)

92ER4 Processed Shotpoint Navigation (68-KB Excel file)


Trackline Maps

Three point-shapefile layers were created: all navigation shots (92ER2 and 92ER4_POINTS.shp), start-of-line shots (92ER2 and 92ER4_FIRST.shp), and start-of-segment shots (92ER2 and 92ER4_SEGMENT.shp). A trackline shapefile (92ER2 and 92ER4_LINES.shp) was generated from the POINTS.shp file using the 'locations to paths' function in Hawth's Analysis Tools (free for download at www.spatialecology.com). It should be noted that the ship's track between points is assumed to be a straight line. The attributes table of the LINES.shp file was manually updated with information for CRUISE and LEG.Trackline maps were created with ESRI ArcMap 9.2, exported to Adobe Illustrator for further editing, and saved in JPEG format. These images can be accessed through the links provided below or from within the cruisenav folder. For more information about the GIS project refer to the readme.txt document located on the software page.

The trackline maps provided in this archive were created using ESRI ArcGIS 9.2 software and then exported to Adobe Illustrator CS2 for further editing. See the readme.txt file in the ARC folder for more details. The maps were later converted into JPEG format by Adobe GoLive. The Gulf States shoreline polygon was derived from a 1:70,000 vector coastline map of the United States originated by NOAA, 1994. The bathymetry line layer, with 100-meter contours supplemented by 20-meter contours on the continental shelf, was originated by NOAA, date unknown. The USGS is the originator of all other layers used. These images can be accessed through the links provided below or from within the CRUISENAV folder.

The trackline maps provided below contain links to the printable profiles, which can also be accessed from the Profiles page.

92ER2_92ER4 Location Map

92ER2 Location Map

92ER4 Location Map

NOTE: Examination of the data, after the cruise, showed that the navigation record for 92ER4 ended on 20 August, 1992, at 17:05Z; no navigation exists for the last 10 min of 92ER4_19(a) or any portion of 92ER4_19(b), 92ER4_20, and 92ER4_21. Copies of these scanned profiles are provided in case navigation is found at a later date. A mix of UTC and local time (UTC - 5 hours) was used throughout the dataset.


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