By Guest Blogger: Jeff Delsescaux
When not being delayed by weather, the crew of the Warwick Project is recording the shipwreck in minute detail. To make sure we make an accurate map of the ship, we use multiple methods including mapping by feature, profiles (cross sectional diagrams), photomosaics, trilateration and direct 1:1 recording.
Mapping by feature is a time consuming recording process that allows for detailed documentation of the layout of the shipwreck’s timbers. Each archaeologist is responsible for recording a different portion of the wreck. All these sections overlap slightly to assist Dr. Piotr Bojakowski and Dr. Katie Custer-Bojakowski with drawing the final site plan.
The first step is to establish a baseline across the section being recorded. Offsets are then taken from this baseline. Every edge, treenail, mark, and feature of the timbers must be recorded. Using a pencil, the data is compiled onto a clipboard covered in Mylar.
Profiles are bit more complex. They record a cross section of the wreck, as if you cut straight down the side of the ship, from deck to keel. First, a string is laid vertically across the wreck, from the turn of the bilge to the top timbers. A few datums are then established within the profile (P06-A, P06-B, et cetera). Using a method called DSM (Direct Survey Method), a number of measurements are taken to datums lying outside the wreck. Once the collected data is plugged into a computer program, commonly referred to as a “WEB,” precise locations for the profile datums can be fixed.
Once they are finished with the DSM, measurements are taken of the profile timbers and, by using a clinometer, angles are recorded at every 30cm.
After all this data is collected, it is time to start drawing. Each diver is expected to produce a 1:10 scale drawing of the area they were responsible for recording. The Assistant Project Director, Doug Inglis, has been diligently making sure everybody continues to make progress on their drawings.
The next step will be making a 1:1 scale drawing underwater by using rolls of acetate. The acetate will be placed on the ceiling planking and held securely in place with small pushpins. Using a grease pencil, the outlines and details of the timbers will be traced onto the clear plastic film. This portion of the project will need to wait for profiles and other measurements to be completed. With the weather being so uncooperative, it is impossible to say when the 1:1 scale drawing will begin.
Reblogged this on Diving | Archaeology.
Making good plan and profile drawings is difficult enough with land-based features. The skills needed to do them underwater are even more impressive.