Illustration in the Field
The drawings that archaeologists complete when they are on site are very important. Archaeologists will draw the features and trenches they dig as part of the recording process.
Drawings can help archaeologists understand the stratigraphy and the features that they are digging. Archaeologists will make sure that each different soil type (or layer - read about this in the Archaeology Glossary) is marked on a drawing, as well as the different things that they can see. For example, the rocks and stones, or wood or bone will all be marked on a drawing with a different key, so that anyone looking at the drawing will understand what the archaeologist saw.
Drawings can be better than photographs (although archaeologists will always take photos too!) because sometimes the photo will not show some small details. Archaeologists can empathise things that they think are important, and make bold lines to show the edges of contexts or features that may not be as obvious in the photo.
On site illustration is often called technical drawing. This is because archaeologists will take lots of measurements for points on the drawing and join them up. This means that the drawing shows exactly what is there - with the right dimensions. So someone sitting in a far away place would be able to look at the drawing, without ever being to the site and be able to know how big a stone was, or how long a wall was. The drawings are all drawn with a scale, so that very large areas can fit onto the pieces of paper. Because the drawings use measurements, it’s not quite the same as an artist sitting down to paint a landscape therefore, archaeologists don’t have to be amazing at art to be able to draw accurate drawings on site.
On site, archaeologists will complete two types of drawings - plan drawings and section drawings.
Plan drawings are what you can see on the ground. Imagine you are a bird looking down from above - a plan drawing is a birds eye view of the feature or site.
Archaeologists will draw any features, or trenches in plan, and will often draw the whole site (if the entire site is being excavated). This lets the archaeologist understand where features are in relation to one another.
Source: The Ness of Brodgar, ' The Art of Archaeological Planning' https://www.nessofbrodgar.co.uk/the-art-of-archaeological-planning/
Archaeologists draw sections of features, in order to understand their stratigraphy. Look back to the Archaeology Glossary to remind yourself what a section is, and how archaeologists understand stratigraphy. Archaeologists ensure that the sides of their trench, or the section that they’ve excavated of their feature is very straight. This is important because it shows the changes in stratigraphy and how thick layers are at that point. It is important to record this, so archaeologists will draw the section - taking care to measure each change in context, and any inclusions that are in the layer (for example stones) or finds that have been left in the section (such as pottery). This section drawing provides archaeologists with a record of the changes, so that they can understand these different layers.
Source: Wright. Internet Archaeology. 20. 'Archaeology, Vector Graphs and the Web'. https://intarch.ac.uk/journal/issue20/1/2.1.html
Plumb and Line
This is one of the more common techniques. Archaeologists will use a base line to measure points off of, this would usually look like the x-axis on the sheet of paper. They will then drop a plumb bob to the point they want to measure. They can then use a tape to measure from the base line to the string of the plumb bob. It’s important that the tape is kept very straight (they can use a line level to check it is level), and that the two tapes are at 90 degrees to one another (perpendicular). This will make sure the point is as accurate as possible.
Triangulation is a little trickier to begin with, but can usually become a faster and more accurate technique. To do triangulation, you will need two tape measures. Again, the archaeologists will drop a plumb bob to the point they would like to measure, then they will use the two tapes to measure from fixed points that they know the measurements of. This can be the corners of the trench, for example. They can then use a compass to measure on the paper from these two points, and the place where the two lines cross is the point. This technique may seem a little more confusing, but when you are in the field is can become very quick, especially if you work with a team of drawers and people can read out the measurements to you!
Tools they need
Just like most drawings that you will see, archaeologists use pencils to draw (4H is the favourite amongst archaeologists) and they use a very sharp point to make sure the line is as neat as possible.
These drawings will be done on tracing paper - or what archaeologists call permatrace). Some paper comes with grids (squares) already printed on, or the permatrace can be clipped to a drawing board that has grid lines. These grid lines will help the person drawing draw to scale - as each little box can represent 1cm, 2cm, 5cm or more!
A line and line level are important for drawings - as mentioned in the Archaeologists’ Tool Kit! Archaeologists can set up a base line (a line to take all measurements off of) and its important that this line is straight to make measurements as accurate as possible. A line level has a little bubble in it that can show you when the string line lies straight.
Soft Tapes and Hand Tapes are also needed to draw. A soft tape - one of those long tapes that can roll up - is often used for the base line, then archaeologists use a hand tape to measure off of it.
A Plumb-Bob helps to measure the exact point that an archaeologist wants to find. Read about it in the Archaeologists Tool Kit!