U.S. Geological Survey Data Series 429
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 subfolder located within the NAVIGATION folder. The accuracy of the LORAN-C varied from 528 to 1,320 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 minutes (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 eight columns:
Field 1: D (DOY, Day of Year)
Field 2: H (Hour)
Field 3: M (Minute)
Field 4: LAT (Latitude, Decimal Degrees)
Field 5: LONG (Longitude, Decimal Degrees)
Field 6: ADTA (Annotated Shot Number)
Field 7: LINE (Trackline Number or Name)
Field 8: FIXT (Fix Type)
90KI1 Annotated Navigation Fixes (36-KB TXT)
91KI2 Annotated Navigation Fixes (71-KB TXT)
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 thirteen 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)
90KI1 Processed Shotpoint Navigation (180-KB Excel file)
91KI2 Processed Shotpoint Navigation (352-KB Excel file)
Three point-shapefile layers were created: all navigation shots (90KI1 and 91KI2_POINTS.shp), start-of-line shots (90KI1 and 91KI2_FIRST.shp), and start-of-segment shots (90KI1 and 91KI2_SEGMENT.shp). A trackline shapefile (90KI1 and 91KI2_LINES.shp) was generated from the POINTS.shp files 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 attribute tables of the LINES.shp files were manually updated with information for CRUISE and LEG.
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 m contours supplemented by 20 m 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.
NOTE: Examination of the data, after the cruise, showed that the navigation recorded for line 90KI1_1 ended on 21 June, 1990, at 23:30Z; no navigation exists for the last 12 min of line 90KI1_1(d) or any portion of lines 90KI1_1(e) and 90KI1_1(f). The navigation recorded for lines 90KI1_2 and 90KI2_6 was also incomplete and represents only sporadic fixes.
The initial survey effort for 91KI2 began on 14 May, 1991, but was ended on 22 May, 1991, due to rough seas and poor weather, as noted in the cruise logbook. No usable data were collected during that time period. The second effort, which is presented in this archive, began on 08 July, 1991, and continued successfully through 26 July, 1991.
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