Archaeological prospection

Archaeological prospection is another way of saying archaeological survey – the process of looking for new archaeological sites. Traditionally this involves extensive fieldwork, surveying landscapes by car or on foot, and is costly in terms of time, money, and resources. Remote sensing survey is a useful alternative, as huge areas can be covered very quickly compared to survey on the ground. It also allows ground to be covered evenly and in a representative manner. For example, rough terrain, or areas where roads or tracks are few, can still be examined using remote sensing. It also allows us to study areas that are inaccessible for other reasons – for example areas where conflict situations prevent access on the ground.

_{Remote sensing can be used to study archaeology in difficult and dangerous places – such as the uplands of northern Yemen. Courtesy of ESA.}

There are different methods available for finding archaeological sites. The simplest way is by using software such as Google Earth, where the satellite imagery is already processed and accurately positioned, to check an area systematically for possible sites and record their location. Specific high-resolution satellite imagery can also be downloaded and opened in other suitable software to carry out this sort of systematic survey. With this method it is usually helpful to work using a grid to make sure the whole area of interest is covered.

_{Systematically covering a survey area using a grid. Imagery courtesy of ESA.}

It is also possible to employ multispectral imagery – images that use parts of the light spectrum that the human eye cannot detect – to look for sites that are either not visible or less clear in ordinary imagery. These techniques rely on the archaeological sites having physical properties that differ from those of the surrounding area. For example, an animal enclosure may have soil that is slightly wetter due to higher levels of organic content from animal manure.

Another option is to study the topography. Many archaeological features will have different elevations to their immediate surroundings. A burial mound, for example, will stand above the local terrain. The ditch around a fort or castle, on the other hand, will appear as a depression within its surroundings. Radar remote sensing provides a great source of topographical data that can help to identify archaeological sites, even if they are not clearly visible on high-resolution satellite imagery.

_{Tells (ancient settlement mounds) in north-eastern Syria are easier to spot using a digital elevation model than satellite imagery. Imagery courtesy of the USGS and ESA.}

Whenever possible, sites located using remote sensing should be visited on the ground to make sure the imagery has been interpreted correctly. It is very easy for an archaeologist to misinterpret features, especially when they are new to remote sensing survey!