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MAGNETOMETER REPORT FOR JULY 25, 2001
This survey was conducted on July 25, 2001 by,
Capt Greg Bounds onboard the M/V Bookmaker.
Objective:
The Objective is to
accurately map the magnetic field of the main pile area of the Corrigans
wreck site using a highly sensitive computer enhanced cesium
magnetometer. Then compare the data collected with known target
locations to try and locate any ferrous shipwreck material, which may
still lay undiscovered on the seafloor.
This site contains many known iron cannon and other ferrous targets that
can be used to calibrate the Magnetometer to the navigational equipment
used on board the tow vessel. By comparing the locations of the known
cannons with the latitude and longitude generated by the magnetometer
software a margin of error can be calculated and new targets if any can
be located and identified.
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EQUIPMENT |
| The equipment used to conduct this survey: |
| Geometrics G-881 cesium magnetometer |
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Cycle rate 10 pulses per second |
| Trimble NT 200D GPS |
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The DGPS provides accurate position data to the logging
computer |
| Compaq PRESARIO 1200 |
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The logging computer creates a file and records the data
generated by the DGPS and Magnetometer simultaneously. After the
survey is complete the data is then processed and compiled into
a workable format. |
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| Software: |
| EO MAG |
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This program brings together the navigational data and the
magnetometer data and stores it on a file. |
| SURFER |
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This program creates the contoured charts of the magnetometer
data. |
| AutoCAD 2000 |
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This program is used to create the complete chart of the
surveyed area and plot all targets discovered. |
Figure: 6 - Aerial photograph of Corrigans wreck site with plots
Figure: 7 - Chart plotting track of magnetomer runs on Corrigans wreck
site
Figure: 8 - Contour chart of Corrigans anomalies
CONCLUSION
After conducting the survey, and processing the data (see
contoured chart on page 5), several large anomalies were discovered.
By comparing the locations of these anomalies with the locations of the
known ferrous objects on Chart A, many of these new targets can be
identified.
Below is a list of targets that were visually identified by the M/V
Bookmaker crew.
Cannon A:
27 43.941
80 22.686
Cannon Pile:
27 43.775
80 22.623
27 43.769
80 22.639
27 43.756
80 22.639
27 43.705
80 22.591
These Cannon positions matched the locations recorded on the ferrous chart
(chart A) within a reasonable distance. This proves the
magnetometer and the navigational equipment together can produce a very
accurate survey.
With this equipment, targets are more readily located and identified.
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