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USGS Coastal and Marine Geology Program

Field Activity Details for field activity 1987-029-FA

Other ID: STRL S5-87-AFR

Status: Completed

Organization(s): USGS, Woods Hole Coastal and Marine Science Center

Funding Program(s):

Principal Investigator(s): Barry Irwin

Affiliate Investigator(s):

Information Specialist(s):

Data Type(s): Electro-Magnetic: Gravity, Sonar: Single Beam, Electro-Magnetic: Magnetics, Location-Elevation: Navigation

Scientific Purpose/Goals: Collect gravity, magnetics and bathymetric data around Senegal, Gambia, Guinea-Bissau, Guinea, and Sierra Leone to a 3 nm grid with internal consistency +/-3 mgals.


Start Port/Location: Dakar, Senegal

End Port/Location: Freetown, Sierra Leone

Start Date: 1987-07-22

End Date: 1987-08-20

Equipment Used: GPS (wh), 12 kHz, Magnavox satellite positioning system, LaCoste-Romberg gravimeter G-179, Geometrics G-856 magnetometer, Gyro compass, GE 810 Correlation sonar

Information to be Derived:

Summary of Activity and Data Gathered: Departed Dakar at 1920 on 22 Jul. 1987. The ship proceeded south to survops area. After completing the two remaining lines in Senegal, all runable lines in the waters off The Gambia, Guinea-Bissau, Guinea and Sierra Leone were completed. Most of the onshore lines run north of Sierra Leone were shortened due to shoals on the eastern ends. Gravimeter S-26 lost its 200 Hz power supply on 2 Aug. 87. The unit was swapped with the unit in meter S-41, which was then shut down. S-26 remained online for the remainder of the cruise and showed no evidence of data tears. Arrived in Freetown, Sierra Leone at 1230 on 20 Aug. 1987.

Staff: Barry Irwin, Carol A. Ryland, Sarah Griscom

Affiliate Staff:
Robin Bouse; Fernandes Caetano and Batiga Mitchel - Guinea Bissau

Notes: Original Center People field contained: Barry Irwin - party chief, Robin Bouse, Sarah Griscom, Carol Renaud.
Project = Defense Mapping Agency Gravity, Defense Mapping Agency Gravity


Senegal, Gambia, Guinea-Bissau, Guinea, Sierra Leone, Africa, North Atlantic;

North: 12.5 South: 6.5 West: -17.75 East: -11.5


photo of Starella


Folger, D.W., McCullough, James R., Irwin, Barry J., Driscoll, George R., and Polloni, Christopher F., 1990, Map showing free-air gravity anomalies off the western coast of Africa; Senegal (south of 15 degrees north latitude) to Sierra Leone: U.S. Geological Survey Miscellaneous Field Studies Map MF-2098-D, scale 1:1,500,000.


Data Acquired

Survey EquipmentSurvey InfoData Type(s)Data Collected
LaCoste-Romberg gravimeter G-179 --- Gravity
12 kHz --- Single Beam
1987-029-FA-SE-001 ( Collection of paper record displays of seismic data (12 kHz) for lines )
Geometrics G-856 magnetometer --- Magnetics
GE 810 Correlation sonar --- Navigation
Gyro compass --- Navigation
GPS (wh) --- Navigation
Magnavox satellite positioning system --- Navigation

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