Gradiometer targets map.

Gradiometer targets map (See large view).

Marine Magnetics generously post-processed the data we collected using Oasis Montaj software as this software is not available for loan or rental and its high cost prevented us from purchasing our own license. Using Oasis Montaj, extraneous data were clipped to enable the modeling of the analytical signal. We used the post-processed data to produce various models of the analytical signal using Surfer mapping software and we plotted the analytical signal and anomaly locations using ArcGIS. Review of those data enabled us to prioritize targets with the highest potentials of representing buried shipwrecks. Attributes considered during our review included the calculated masses of individual anomalies and the density and spatial extent anomaly clusters. Five target clusters were identified within the study area; of these, Targets 2, 3 and 5 appear to have the highest probability of representing buried flotilla shipwrecks based on the mass and distribution of the anomalies that compose them. The relatively similar burial depth of those anomalies, 1.0 to 3.0 m, also corresponds fairly well with the observed burial depth of the known War of 1812 shipwreck that is represented by Target 2.


The Marine Magnetics SeaQuest 3-Axis gradiometer generally is more suitable for high resolution mapping of known shipwrecks than for searching large areas for undocumented submerged cultural resources.

In general, we found the gradiometer easy to assemble and operate, but we had trouble deploying and retrieving it. It is best deployed by two or more people walking it into the water and towing it to the survey area if a winch and adequate deck space are not available.

It provides the ability to precisely ascertain the locations and burial depths of significant ferro-metallic objects that can aid in the delineation of buried shipwrecks.

Targets near known War of 1812 shipwreck in the Patuxent River.

Targets near known War of 1812 shipwreck in the Patuxent River.




Comments, suggestions, and questions can be directed to Dr. Susan Langley


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