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Drayton Hall Survey and GIS

A Geographic Information System

The ceiling of Drayton Hall is only 600 square feet, which is relatively small for the application of GIS; however, by applying methods used for large scale analysis, (locating roads, identifying geological faults), similar patterns were identified on this much reduced scale.

The use of GIS was an experimental aspect of this project that demonstrated encouraging results in its potential use for both short term evaluation associated with treatment, as well as longer term monitoring.  Once all of the data were collected and digitally drawn in AutoCAD, each condition was then imported into Arcview. From this point Arcview was used to create regression modeling to identify the correlation between the existing crack patterns and variables associated with them such as their distance from each other. Spatial analysis was conducted using three ArcGIS extensions including Spatial Analyst,  3-D Analyst and Geostatistical Analyst in order to find the spatial structure of the cracks as well as to create predictive maps to identify the location of potential threats to the surface.
40 pix spacergis regression
The final map created was the result of a regression analysis. This process statistically applied several different variables, each of which was calculated by its defined weighting. The end result is a map that shows potential unseen "threat" to the ceiling based on visible clues.

In preparation for treatment, the 1991 documentation of conditions was extended to include size of cracking based on width, direction of vertical displacement of cracking, and size of cracking based on vertical displacement. Additional collected data included exact locations of major ceiling features to assist in the creation of a CAD drawing, to be used as a base map for all survey data, as well as treatment documentation. Using triangulation from two datum points, measurements of over 600 ceiling points were taken which included major decorative elements as well as the intersection of all major crack intersections.
gibbs image
While the cracks were initially considered the most important aspect, the actual fields of unbroken plaster between the cracks proved to be valuable as well. Note that most of the large areas of detachment (blue) are in direct contact with the largest unbroken fields of plaster (dark mustard and gray) .

ceiling joists
Included in the ceiling assessment was a review of previous treatments including the pouring of plaster from above between floor joists in an attempt to rebuild lost and broken keys.
The Great Hall
The 2002 Geographic Information System (GIS) assessment provided the ACL with a new way to study and identify the areas for potential treatment based on proposed correlations between the cracks and the detachment,  allowing us to approach treatment more selectively and more intelligently. By looking at the more clearly defined areas of potential threat from the 2002 GIS and by turning to the information related to the 1978 treatment, we were able to build confidence in the potential results of our selective injection method. The introduction of newer diagnostic technology provided us with the evidence needed to treat fewer areas with greater confidence.