Skip to 0 minutes and 8 secondsWhen you hit the launch button, this is the screen that you'll see. Before we start doing the exercise, let's first look at the controls. In the upper left-hand corner, we have a zoom bar. If you hit the plus (+) button, you will zoom in. If you hit the minus (-) button, you will zoom out. You can also drag this or use the scroll button on your mouse. In the upper right-hand corner is a Greyscale button and an Interpretation button. Greyscale, seen here, shows you a geophysical plot overlying a satellite map. The Interpretation button is a drawing of that geophysical plot. Below the Greyscale and Interpretation buttons is a slider that influences the transparency.
Skip to 0 minutes and 45 secondsAll the way to the left, fully transparent. All the way to the right, you get a solid image. And in the middle, between, is something semi-transparent.
Skip to 0 minutes and 58 secondsNow let's do some interpretation. First, click on the Greyscale button and locate the slider all the way to the left on full transparency. Can you see any of the archaeological features in this image? The rectangular shape of the fort is visible, but there's very little of the extra-mural settlement in this area that can be seen. Now move the slider to its halfway position, or thereabouts. Now you can see the overall size of the settlement inside and outside of the fort walls relative to the modern landscape. Now zoom into an area for closer inspection.
Skip to 1 minute and 41 secondsAnd then move the slider all the way to the right to reduce the transparency. You will see that while some of the lines revealed by geophysical survey are still very visible and clear, for example here, many of these features become less distinct. Staying at the same zoom and transparency, click on Interpretation. This should help to reduce the fuzziness or noise of the geophysical survey by indicating the results that relate to structures, mostly roads, walls, and ditches. Remember, though, that this drawing is an interpretation of the geophysical survey results, and a different surveyor may be more or less confident in their interpretation of some of these features.
Skip to 2 minutes and 21 secondsIf you zoom out a bit, hopefully the interpretation will resolve into a pattern that is easier to understand. The black outlines ditches, which often formed boundaries between plots of land, while grey shows the outlines of buildings and other structures. Black blobs are pits or holes. Sometimes a lack of indication can also be useful. For example, let's look at the fort. The break in the ditches and banks show the location of a road and gate into the fort. Or these squarish blocks in a rectangular shape here indicate the presence of a barrack. To the southeast of the fort is a native settlement. Press the Iron Age Settlement button to the right if you need help locating this feature.
Skip to 3 minutes and 12 secondsHere you can see the Iron Age settlement outlined in a pink box, remembering that the negative anomalies are black and the positive anomalies in grey. Sometimes, though, geophysics does not always reveal clear results. Click the Temple button to the right of the screen to locate Roman temples that were discussed in week 4. The location of the temples, outlined here in the pink circle, has been known from previous excavation. But note the general shape or outline of the temple is not seen in the geophysical survey or the interpretation plot.
Skip to 3 minutes and 51 secondsWhile there's no substitute for excavation, the layering and interrogation of evidence in this form is significant when it comes to interpreting a site without or even before putting a spade in the ground. Now it's your turn.
Exploring magnetometry exercise - explanation
In the next step you will have an opportunity to explore the buried landscape of Roman Maryport through the magnetometry data recovered by Drs Alan Biggins and David Taylor for the Senhouse Museum Trust. We have overlaid Biggin’s and Taylors plots on a satellite image of the modern landscape.
You will be able to switch between viewing the greyscale plot, a basic representation of the anomalies identified, and Biggins and Taylor’s interpretation plan of that data. You will also have a chance to examine specific features and identify others.
In this screen recording, Rob Collins shows how to get the most of of the exercise, demonstrating how to:
- zoom and move around the map
- switch between the greyscale plot and interpretation
- adjust the transparency of the magnetometry plots
- jump to features we have highlighted
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