ONCE MORE INTO THE BREACH: USING GPR (AGAIN) TO FIND AN EASY TARGET HIDDEN IN PLAIN SIGHT AT WEST POINT, NEW YORK

Over the last 25 years, four separate investigations used Ground Penetrating Radar (GPR) to hunt for two large “cannon” known to be buried in the parade field at West Point. All attempts to date have been inconclusive, until now. Our approach is new because we took a step back and recognized “the forest for the trees,” as the saying goes.

The 12-inch diameter coastal artillery mortars (hereby referred to as cannon) are each 15 feet long, 45 tons of metal, and were mounted on 50-ton carriages on a concrete pad. They were used between 1902 and 1931 to give US Military Academy Cadets a place to train on coastal artillery weapons. Notable Army officers such as MacArthur, Patton, and Eisenhower all would have used these cannons while they were Cadets. When coastal artillery training was no longer in fashion for the US Army, the cannon were left in place and buried to expand the parade field, known as The Plain. Using GPR is an attractive method for geophysical investigation because of the target properties, the flat ground, and the fact that our department owns the machine. The challenging issue is that photogrammetry research from old aerial photos places the cannon directly underneath two sets of permanently-mounted metal bleachers built on gravel pads. It is impossible to fit the GPR under the bleachers for an adequate survey, and the metal causes too much interference in the data. But there is hope for a new approach.

Previous studies conducted widely-spaced single GPR line surveys, then chose single hyperbole along a line to conduct very targeted high resolution grid surveys hoping to find a single cannon. This methodology was repeated over the years with newer GPR technology, newer software, different researchers to interpret the data. All were inconclusive. In this renewed approach we take a broader view, using high resolution grids but patching them together to capture a larger area and look for larger patterns and context in the subsurface. Here we map the whole coastal artillery mortar complex, instead of just trying to find the cannon. The results are reassuring for student-led independent study, reinforcing the importance of critical thinking and context and holistic understanding. It has also been a lesson in persistence and resilience – we know the mortars are underground, but will we hit our target?