So far we have discussed the different geophysical methods that we use in maritime archaeology to understand submerged landscapes and to find shipwrecks. However, you haven’t had the opportunity to engage with the data yourselves … until now. In the attached file you will find the processed data from a bathymetric survey of the sea floor.
The data is from an open access source (the Channel Coastal Observatory). We have processed files for part of the coast off southern England and converted them into the image you can now download through use of a geographical information system (simply, a piece of computer software that lets us bring lots of different pieces of spatial data together). We have then extracted a large area as a file for you to look at.
Your challenge is to find as many shipwrecks on the attached image as possible. We are not going to say (yet) how many there are to be found, but, there are more than six…
How to find anomalies/shipwrecks?
There are a number of different things we look for when trying to identify new sites in survey data. First, you look for anything that stands out as different to, or that disrupts, the general pattern visible in the seabed for a given area. In a perfect world we would have a flat seabed and all wrecks would rise vertically out from them. This would allow us to see a wreck just as if it were sailing on the surface of the sea. However, the wrecking process and the nature of the seabed means that this is very rarely the case. Instead we are looking for ships and parts of ships. One of the best indicators of a wreck being in a given area is disruption to local sedimentary process, i.e. the patterns on the sea floor change; scour pits may be dug into the ground near the wreck as the water speeds up around it and/or material may mound up around the wreck.
The next thing to do is to keep an eye on scale. In the image you can download below we have provided a scale bar and put a 50x50m grid over the image (please note you can turn the grid off if you find it distracting). There are many geological structures that you can find on the seabed that can look like shipwrecks, but, either they are far too large, or far too small for it to be likely.
However, the most important thing in the identification of shipwrecks from geophysical data is experience. When we work with survey datasets we generally refer to most potential wrecks as ‘anomalies’ until we are sure that it is a wreck. As such, don’t worry about being wrong, but try to make sure that you have a good reason for picking out what you think may be wrecks. Is it because you can see a scour pit/change in the seabed? Is it because there is a structure that looks like a ship!
To take part in this activity download the pdf attached to this step. Using a viewer on your computer or mobile device zoom in and scroll over the seabed. When you find something that you think looks like a wreck take a screen grab of it and post it on Padlet. We will read through the comments and answer any questions you may have. Good luck!
© University of Southampton, 2015