Aerial photography is a surveying technique that involves taking a photographic record from satellites, aircrafts and balloons, to aid with the detection of buried archaeological remains and features, which may be difficult to identify at ground level.

There are two types of aerial photography;

• Oblique – Oblique aerial photography involves taking a photograph from lower altitudes at an angle. This gives a better perspective and a pictorial effect, and allows for identification of earthworks.

• Vertical – Vertical aerial photography involves taking a photograph from great heights directly above an area. This gives a bird’s eye view of an area, allowing for easier map making and identification of crop marks.

Fig. 1: There are two types of aerial photography; oblique and vertical.

These aerial photographs can show numerous phenomena, some of which are sometimes not from archaeological origins. These phenomena include:

• Crop marks – These types of marks develop when a buried wall or ditch increases or decreases crop growth; this is due to the feature affecting the availability of moisture and nutrients in the soil.

Fig 2. An example of a crop mark. You can see in the excavation site the ditch that is affecting the crop’s growth.

• Soil marks – These marks are caused by changes in the subsoil colour, when a plough brings part of the buried feature to the surface.

Fig. 3: An example of soil marks. After this field had been ploughed, this buried feature had parts brought to the surface which has caused discolouration in the soil.

• Earthworks – This phrase is used to describe any features seen in relief. These are also known as shadow marks when viewed from the air.

Fig. 4: This is an example of an earthwork. This particular archaeological site is an abandoned Medieval settlement.

It is from these phenomena that we’re able to identify whether there is buried archaeology in an area which can then allow for an in-depth investigation.

References:

Balme, J., Paterson, A. 2006. Archaeology in Practice: A Student Guide to Archaeological Analayses. Oxford, UK: Blackwell Publishing. Pg 218.

Renfrew, C., Bahn, P. 1991. Archaeology: Theories, Methods and Practice. London, UK: Thames & Hudson. Pg 249-53.

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