While we mostly used triangulation to delineate interesting rocks on our drawing, we found that the results worsened as we approached the edge of the trench, as the inaccuracies of the method became a high percentage of the measurement taken. Therefore, for the rocks around the centre of the trench, we decided to use offsetting and ‘swinging the tape’ in order to record these rocks.

Having pegged a tape horizontally along an edge of the trench, a second tape was used to measure horizontal displacement from this edge. In order to do this accurately, an angle of 90 degrees must be obtained between the two tapes. Rather than measure with a compass or optical square, we opted for the quicker method of holding the end of the tape firmly on the rock corner and then adjusting the tape so that it read the lowest reading possible, as the lowest reading would be obtained when there was a 90 degree angle between the rock-point and the baseline tape.

Written on August 8th, 2012 , Diploma Year One, Techniques

Whilst this technique obviously has many applications, it was encountered in the process of recording significate rocks within a trench otherwise full of rocks so is written to demonstrate this scenario.

You will need two surveyors tapes, preferably of different colours as that makes it much easier to record and minimises errors (proven by experimentation!). Secure each tape at a corner of the trench. At the start of the recording, we had a white tape and a yellow tape, so labelled the trench corners as W (for white) and Y (for yellow).

Taking care to keep the tapes horizontal (not parallel to the ground as we were on a crazy slope) bring the loose end of the tapes together at a corner of a rock. Note the readings on both tapes. Take readings at all interesting points of the perimeter of the rock, as these will describe the outline when you come to draw it.

Nicky demonstrating the multi-colour tape technique. July 2012. Copyright K Bragg

Once your rock has been described as a series of Y and W readings, it is time to draw! Drawing as soon as possible enables you to see if it has come out at all reasonably-shaped. Remember here that you are interpreting where the edge of a rock is, and the scale at which it is to be drawn will not allow much accuracy of depiction, so even when you do this carefully it is perfectly possible to end up with something preposterous.

You will need to have prepared your drawing with a scale outline of the trench (in our case we used 1:20 as a scale) with your Y and W points (or whatever you want to call them) marked on the drawing. You will need a pair of compasses with which to mark out the distance from Y or W – put the point of the compass against the scale rule and measure out the appropriate reading. This gives you the distance scaled to match the drawing. If you dislike using the scale rule constantly, it is much easier to draw out the scale as a reference on your drawing. We drew the 1, 2 and 3 meter points, and then another metre with finer subdivisions so that you can put the point of the compass at the correct number of metres away and then adjust for the sub-metre fraction. Which is harder to explain than to do. If you want 2.24 metres, you put the point of the compass at the 2 mark and then add on the 0.24. This avoids the need to mark in graduations for every metre, and stops you wearing a hole in the zero point!

Scale for drawing.

Using the compasses, draw arcs of the appropriate length from the appropriate corners and where they cross is the point on the rock that you measured (hopefully!). Repeat for all the points you recorded and then freehand draw the appropriate outline. For the more interesting rock shapes this was aided by a sneaky vertical photo of said rock.

Written on August 3rd, 2012 , Diploma Year One, Techniques

Today started with half an hour spent backfilling the site of last year’s excavation: light-coloured limestone was moved from the spoilheap to the excavation (the light colour denoting lack of exposure and therefore was from the excavation, whereas the darker limestone was a clearance cairn) and then a covering of soil tipped on top. As this was quite tiring, there was a break immediately afterwoods so we could recover!

Site Reconstitution: backfilling last year’s excavation. July 2012. Copyright K Bragg.

As I’d turned up a week after the start of the dig, the trenches were already open and being cleaned, so my first task (and one that was to take several days to accomplish) was to produce a drawing of significant rocks within a trench. The reason for this is that we are looking at potential stone-built structures and amidst the mass of visible stones, we wish to pick out any that could be meaningful.

First significantly-large rocks plotted. July 2012. Copyright K Bragg

Written on July 15th, 2012 , Diploma Year One, Excavation Notebook, Fieldwork

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