Author: Mattie Bennett, Project Archaeologist
Field survey, or Landscape archaeology, is the way in which archaeologists are able to assess the geography of an area to examine whether it is a viable site to excavate. There are a multiplicity of ways in which this can be undertaken, here we are going to discuss how we specifically use field walking, aerial photography and systems such as the Global Positioning System (GPS) to undertake field survey.
Field Survey is often a great tool which can be used to great effect on excavations, in both the pre-excavation and post-excavation stages of a site. The Field Survey not only allows for the initial search for archaeological sites, but also allows for collection information regarding specifics of a site, such as the geography and how the site may have been organised (Banning, 2002). This allows archaeologists to be more specific in their approach and ask narrower questions of a site, for instance if we can see dark rings approximating 8-10m in diameter, we could be expecting a site that is Bronze or Iron age in origin (See Lara’s previous blog on Roundhouses).
One of the easiest ways to conduct a Field Survey is to create a transect, or simply known as field walking. This is where an archaeologist walks in a straight line across a length of a prospective site. Here they can take their time scouring the surface for signs of previous use or artefacts. Indeed in recently ploughed fields finds can be brought up from deep within the soil and can often be seen on the surface – these can include anything from knapped flint to ceramics. Field walking can provide a very good initial assessment of a site and may give some indication to what eras of occupation there may have been on the site.
Aerial photography is another element of landscape archaeology which is incredibly valuable. Some features of the landscape may just be far too large to be seen on the ground, or even hidden within the landscape. Some may remember the summer of 2018, where a drought in the UK had one benefit for archaeology – hidden sites of the countryside became visible from the air due to the differential between the dry ground and the disturbed ground of the past. Many of these sites would have been incredibly difficult to see if not for aerial photography.
In addition to the wider approach of Field Survey, there are often surveyors on site who can use Real-Time Kinematic (RTK) devices such as Trimble or Leica. RTK uses global navigation satellite systems (GNSS) such as the USA’s GPS or the EU’s Galileo to take more accurate measurements (Wanninger, 2008) and is a very mobile way of taking these measurements.These RTK devices can be used on the micro scale of the site to record the individual features excavated by archaeologists. This can provide very accurate data points which can then be turned into a Survey Map which by the end of the excavation can then be presented as an incredibly useful visual aid.
There are many other techniques you can use for field surveys such as Geophysics or Lidar (recently used to uncover Mayan cities in the Yucatan peninsula! (Inomata et al., 2020)), which we may come back to in a future blog! For now lets see surveyors in action and look at some data from our very own site at Hawstead.
Here is one of the survey maps from our own excavations at the Hawstead community project! This is an example of how RTK devices can be used on site. First we have a large aerial photo of the site, it has very clear demarcations of large circular features!
Highlighted is an area that was targeted for excavation, which can be seen below.
From this trench, the surveyor on site took the GPS points of excavated features.
Now the problem here is that although we can see all the labelled points, it is quite difficult to see what is actually happening within the area. That’s where GIS software and the design team comes into play! They have the technical knowhow on how to turn these series of points into something concrete and representative of the archaeology!
And this is one of a series of survey maps, we can see the excavated outline of two ring gullies intersected by a series of pits! Being able to take accurate measurements and then collate that into readable and visual data means that we can have access to solid information which can help us inform further archaeological excavations for a site and aid in the write up for projects.
So there we have some of the basics of Field Surveying and how archaeologists can use surveyors on site to great effect!
Inomata, T., Triadan, D., Vázquez López, V.A., Fernandez-Diaz, J.C., Omori, T., Méndez Bauer, M.B., García Hernández, M., Beach, T., Cagnato, C., Aoyama, K., Nasu, H., 2020. Monumental architecture at Aguada Fénix and the rise of Maya civilization. Nature 582, 530–533. https://doi.org/10.1038/s41586-020-2343-4