2012-06 Final Report

Download “2012-06 Final Report” MT-2210011-NC-04-Geophysical-Laser-Scan-Report.pdf – Downloaded 311 times – 9 MB

Geophysical and laser scan surveys were conducted at the Longfellow House – Washington’s
Headquarters National Historic Site (NHS), Cambridge, Massachusetts in August, 2011. This work was
undertaken as part of the Archaeological Survey Technology, Data Integration, and Applications (ASTDA) Workshop. This workshop was funded by the National Center for Preservation Technology Training and supported by the Joukowsky Institute for Archaeology and the Ancient World, Brown University, and Harry R. Feldman Survey, Inc.

This work helped identify and map modern landscape features as well as previously unknown and significant landscape and archaeological features including structural foundations, potential garden beds, and colonial-period structures. Ground penetrating radar (GPR), magnetic gradient, conductivity, and electrical resistance survey methods were employed. The GPR and magnetic gradient most effectively identify architectural features in the form of rectilinear anomalies that most likely represent building foundations, or basements of structures pre-dating the Longfellow House – Washington’s Headquarters National Historic Site. The GPR and magnetic gradient methods were also most effective in identifying what appear to be colonial-period landscape features. These two geophysical methods greatly complimented each other in anomaly identification, providing insight to possible material composition of some of the potential archaeological features. The conductivity survey mostly identified modern features such as utilities and existing pathways, but also complimented the GPR and magnetic gradient surveys in mapping some of the colonial-period landscape features. Due to time restrictions, the resistance survey sampling rates were rather coarse (1 m x 1 m sample spacing with 0.5 m electrode spacing) and did not reveal any potential archaeological anomalies. In some instances the geophysical survey anomalies can be compared against features from previous excavations, which reveal that while the geophysical surveys (GPR & magnetic gradient) identified a basement feature pre-dating the existing structure) they also (with conductivity) identified a cultural feature that was not identified during excavations, thus revealing that geophysical surveys are necessary and complementary methods for site investigation.

Use of the TR/CIA Resistance Meter during the ASTDA Workshop

Use of the TR/CIA Resistance Meter during the ASTDA Workshop

3D laser scanning surveys were used to construct a high-resolution model of the Longfellow House -
Washington’s Headquarters National Historic Site and its immediate environment. Geophysical survey results and 3D laser scanning models were integrated into 2D analytical (GIS) and 3D visual (Pointools) environments for enhanced site analysis and the development of new visual methods for data presentation and delivery.

This project was made possible through Grant MT-2210-11-NC-04 from the National Center for Preservation Technology and Training (NCPTT).

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