Thursday, September 10, 2009

How to be an Archaeologist: The Radial Contour Survey

We’ve written before about close contour surveys and how important they are in archaeologing circles. Without them test pits and trenches couldn’t be accurately placed, the terrain would be less easy to understand and spot levelling during excavations would be rendered almost meaningless, reducing other records, such as the stratigraphic matrix, to a comparatively ineffective load of old codswallop.
In short, without a close contour survey an archaeological dig amounts to little more than treasure hunting.

We’re not going to rehash the detailed methodology of contour surveying here. You can look up our previous articles on the subject if you’ve forgotten. However, by way of a brief recap, a baseline is created (generally bisecting the highest points of the site, if possible) and a series of evenly spaced ‘ribs’ established at right angles along it. The dumpy is then set over the individual ‘spine’ pegs and the stadia staff moved along the ‘ribs’ until the relevant contour is located. After this it’s a simple job of recording the distance from the baseline to the relevant location before moving on to the next contour. Once collated all the information is transferred to the finished map.
Last time we wrote about this subject, however, we forget to include a blank record sheet for anybody wanting to conduct their own survey who couldn’t be bothered creating one for themselves. Now might be a good time to correct this omission.
Let’s start off with a combined ‘Benchmark Record’ and ‘Spine Record’. (We’re being incredibly generous here. By rights we should be getting squillions of quid in copyright royalties for the amount of work we’ve put into these things, but we’d rather forego our fees and make sure that bone-idle amateur archaeologists out there don’t go round buggering up important sites.)

As always, click on the image above for the full-sized version. Rotate it 90 degrees before you print it up and it should fit perfectly on an A4 piece of paper.
Next up we have the ‘Ribs’ record sheet, again designed to fit on size A4. If you’re having difficulty filling these in correctly then please refer to our previous posting on this topic.

There are times during most contour surveys when a simple ‘spine’ and ‘rib’ model won’t suffice, when a feature runs almost parallel to the ribs, for example, and the distance between the spine pegs is insufficient to capture the sudden changes in the contours. At other times, when an area of the site is full of humps and crannies and stuff that fall between the ‘ribs’, again the baseline method is unsuitable.
(Is everybody following this? I’m having difficulty myself here. Comments explaining back to me in proper, understandable English what I’ve just written would be welcome.)
At times like these the ‘Radial Contour Survey’ comes into its own.
Now, observant dumpy owners out there will already be aware that just below the level itself is an adjustable dial for measuring angles, as shown in somewhat blurred photograph below.

As a rule, radial surveys come into effect either at the end of, or part way along, an already established baseline. The principal mechanics of the radial survey are basically the same as those for the ‘ribs’. The dumpy is set up over the relevant ‘Spine’ peg, aligned with the baseline, and the ‘Angle-o-meter’ set to nought degrees. Then the level itself is turned relative to the dial, to establish the first angle of sight. The size of this angle depends on the complexity of the features you’re surveying, and how bothered you can be with the finer details.
Using the usual stadia staff and tape measure method, a ‘Radial Rib’ is marked out, the relevant contours/ spot levels taken, and the dumpy rotated by the same number of degrees again clockwise for the next set of figures. Eventually enough data will have been collected to transfer the results to the finished map.
Does this make sense?
I hope it does because even I’m starting to get bored of it now.
Anyhow, all of these measurements need recording, and because, once again, the chances are you can’t be bothered designing your own ‘Radial Record’ sheet, here’s one we made earlier.

Now go out there and make sure you do all this in a responsible, professional fashion, like what we do.
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JahTeh said...

I cannot believe there are no comments for this enthralling post!

What are people thinkinzzzzzzzzzzzzzzzzzzzzzzzzzzzz

Brian Hughes said...


Some matters are beyond rational thought.

David Sankey said...

Very useful for training purposes - thanks