Monday, July 18, 2011

Update - Maritime Mapping

Welcome to the final week of the 2011 Arcadia field season! Many thanks are due to everyone who contributed their valuable time and energy to helping us understand the nature of the antebellum community at Arcadia Mill. The field school finished this season's final test unit excavation at the end of last Friday, and we are now going through the process of back-filling, performing maintenance on our equipment, and preparing the artifacts that we have recovered for the lab component of our project.

Our maritime survey has been an outstanding success. Thanks to their work, we now have the entire extent of Pond Creek within the boundaries of the property mapped, along with associated features like cut timbers, cut shorelines, vertical pilings, and sandstone scatters. The hand-drawn maps from this work have already been geo-referenced and digitally integrated into our Geographic Information System for analysis. We've also been able to do some geophysical work in the creek with the underwater magnetometer.

Maritime mapping techniques are a little different than what terrestrial archaeologists are used to. Since it is not efficient to section out a grid in such a large area as a creek bed, our divers have established what are called baselines. At Arcadia, these baselines have a starting and ending point known by their UTM coordinates. The crew was then able to measure the distance and angle from their baseline to the feature that they wanted to map. Once integrated into our GIS, the architectural features can be easily compared to the vector data that we already have such as topographic contours, US Geological Survey soil composition, areal photographs, and historic maps.

The maritime component has also been able to take some underwater photographs of features associated with the mill this summer. Thanks to the recent dry weather conditions, the creek was clear of the brown tannin from local oak trees that would obscure visibility. Moreover, the actual water level of the creek has been low enough to make for good lighting conditions.

This image depicts part of a circular brick concentration near a square-cut channel in the creek's bank. This could very well be the location of the bridge because of the earthworks that had been done to allow for easy access to the water.

Thanks to the action of the flow of water over the years, the creek bed is littered with sandstone scatters like these. While some were probably intended to help channel the flow of water, it is possible that some were also used to create a stable foundation to build structures upon.

The maritime component of our field school was always on the lookout for squared timbers. To the left you can see a cut board with a cut circular hole. Mortis and Tenon construction was a popular alternative to relying on expensive nails for holding structures together. The image to the right is vertical piling that might have been for a bridge or wooden support structure.

This video should give you an excellent impression of what it was like as a diver during the survey. As you can see, identifying cultural features and telling them apart from the natural character of the creek bed can be quite a challenge!

No comments:

Post a Comment