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Magnetometer and Ground Penetrating Radar
(GPR) surveys were performed across the site
with a line spacing of 1.5ft.
The results of
the magnetometer survey were inconclusive
for burials.
They did,
however, image features such as the remnants
of a fence that once existed in the
churchyard.
The results of
the GPR survey were much more useful for the
identification of unmarked burials.
Numerous
hyperbolic reflections in the GPR survey
images indicate that there may indeed be
unmarked burials at the site of the
Historical Society of the Phoenixville Area.
The hyperbolic
reflections, caused by diffraction of the
radar wave off the edges of discrete objects
in the subsurface, could be associated with
coffins.
To support the
interpretation of unmarked burials, all GPR
profiles were analyzed for these diffraction
hyperbolas.
With a survey
line spacing of 1.5ft, the three dimensional
results of the GPR survey over a coffin
should show continuity across two or more
GPR survey lines.
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 GPR results of the cemetery site
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Combined magnetometer and GPR results of the cemetery site
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The position of each
GPR anomaly was marked with either a gray or
a black circle.
Black circles
indicate GPR anomalies that strongly
resembles the anomaly that would be expected
from a coffin while gray circles indicate
GPR anomalies that moderately resemble the
anomaly that would be expected from a
coffin.
Anomalies at
the locations of gray circles are hyperbolic
but lack some aspect of the strength of
resemblance of the black circles (i.e.
shallower in depth, smaller in size, weaker
in signal strength).
The continuity
of the GPR anomalies across multiple lines
and the presence of so many hyperbolic
reflections across the site indicates that
there are numerous unmarked burials at the
site of the HSPA.
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