So you’ve revealed your first context or feature, but before you can dive straight in an excavate it you need to create an accurate drawn record of its shape and position within your trench. We enlisted our Venturers to demonstrate how to do it in 8 easy steps.
First up, you need to make sure your trench is nicely cleaned back, that means all the lose earth is removed so that you’ve got the best possible view of your shiny new context.
Next, set up your baseline. This is a temporary measure set up along the trench edge that will allow you to accurately measure the context’s position inside it.
Run a length of string between the two nails (long enough to cover the extent of your context) and pin it along the trench edge. To this attach your fixed tape and check it’s perfectly horizontal with your trusty spirit level.
Each of the four corners of your trench will have pre-plotted coordinates, it’s important to record the coordinate of the trench corner that your line begins from, so that the context can later be located in relation to whole site plan.
Having your sheet of permatrace firmly attached to a clean drawing board is essential (mud splatters & tea stain etc will not be tolerated), and wind is not your friend! So use masking tape or bulldog clips to fix it in place.
Site Code (your plan will be pretty useless without it!)
Scale (usually 1:20 for plans)
Description of Context
A North Arrow
Who it’s drawn by (a true artist always signs their handiwork!)
Draw the base line along the bottom of your permatrace (remember that 1 square = 20cm, so if your baseline is 4m long it should cover 20 squares), and you’re set to begin!
This is where your skills at filling out dot-to-dots come into play! Using the second tape measure and the plumb-bob you can start to plot the shape of your context.
Dangle the plumb-bob over the first point of the context you want to draw, and run the second tape measure between the line of the plumb-bob and the fixed measure (making sure the two tapes cross each other at a right angle for an accurate reading.)
On your permatrace, count out the horizontal measurement along the baseline (or ‘x’ axis), and then use the vertical measurement from the mobile measure to count up the ‘y’ axis, and then draw a small dot.
So if your first point is 80cm from the corner along the baseline, and 60cm up from the baseline, the first point would be located 4 squares across and 3 squares up. Simple!
All you have to do now is continue to take measurements at regular intervals, plotting the dots on the plan as you go, and when you’re done it really is just a case of joining the dots!
And there you have it!
Once you’ve got this process down you can then start annotating the drawing with further detail, using different line types to show changes in boundary, and, if it’s a cut, adding hachures to denote the type/steepness/length of slope. Here are a few basics to get you started…
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