ALPH 98013 Sparker Field Navigation Data and
Shotpoint Navigation Data:
Click on each of the survey areas for a more detailed map and to view the seismic
Click on each of the survey areas for a more detailed map and to view the
Dumpsite Area | Mosaic Area
Raw Navigation Data:
The raw navigation was collected using a USGS differential GPS system (Ashtech).
These files represent the data that was originally recorded on floppy disk aboard
ship. The data are in NEMA format. WARNING:
These data have not been checked for errors. Use
To aid viewing of the original raw navigation data, each data entry was reformatted
(removing the NEMA codes) by filtering the raw data files through a UNIX awk script.
Every navigation fix from the original data has been preserved, however.
The navigation is stored in ASCII files using six fields separated by tabs, with
each file representing a separate julian day (i.e. jd254web.txt). Navigation fixes
are at 10 second intervals. The start and end of each line is marked within each
reformatted navigation file.
- Field 1: Date and Time (julian day:hour (GMT):minute:second)
- Field 2: Latitude (degrees and minutes)
- Field 3: Longitude (degrees and minutes)
- Field 4: Speed (in knots, computed from the navigation)
- Field 5: Heading (in degrees, computed from the navigation, i.e.
course made good)
- Field 6: Average Water Depth (the average of depths for 10 second
Depths are in meters, but have not been corrected for the depth of the transducer,
which was about 1 m below the sea surface