USGS Cruise MGNM 99023 Chirp Survey
Field Navigation Data & Shotpoint Maps
Shotpoint Navigation Data
Raw Navigation Data
The raw navigation was collected using a differential GPS system (Ashtech).
These files represent the raw data recorded on floppy disk aboard ship. The data
are in NEMA format. WARNING: These data have
not been checked for errors. Use with caution.
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. jd208web.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 (decimal degrees)
- Field 3: Longitude (decimal degrees)
- 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: Water Depth (derived from a Furuno digital echo sounder).
Depths are in meters, but have not been corrected for the depth of the transducer,
which was about 1 m below the sea surface
Download Files (click on the Julian Day):
Julian Day: 208 | 209
| 210 | 211