A POWERFUL TOOL FOR THE DIGITISATION OF THE PAST
AS A VALUABLE RESOURCE FOR STUDYING AND UNDERSTANDING THE PAST, HISTORICAL MAPS CAN PROVIDE IMPORTANT INFORMATION THAT MIGHT OTHERWISE NOT BE AVAILABLE TO US, BUT THEY CAN ALSO PRESENT SOME CHALLENGES IN THEIR USE AND INTERPRETATION. MAEASaM’s RESEARCHERS, RENIER VAN DER MERWE AND ED BURNETT BRING TO LIGHT THIS LARGELY UNDER-REPRESENTED BUT POWERFUL TOOL FOR THE DOCUMENTATION OF AFRICA’S ARCHAEOLOGY IN THE MAEASaM PROJECT..
As the second largest continent, Africa’s history is as diverse and dynamic as its present. With a deep history stretching from the hominin footprints at Laetoli, Tanzania to the pyramids of Giza and the monumental architecture of Great Zimbabwe, reconstructing such deep and diverse archaeological landscapes requires multiple techniques, methods, and lines of enquiry. Currently, Africanist archaeologists are using remote sensing techniques to reconstruct past landscapes, such as ground penetrating radar, satellite imagery, and light-based detection methods, commonly known as LiDAR. These techniques are revolutionising our understanding of past landscapes; however, another powerful yet largely under-represented tool is to be found in Africa’s historical maps.
A brief review of the literature reveals the extent to which maps have been part of our global human story. From the oldest surviving map – the Imago Mundi or the Babylonian Map – dating to around 600 BCE, to the most detailed global mapping apps such as Google Earth Street View and Google Maps that help billions of humans navigate their daily movements today, it is no surprise that maps have been hailed as ‘humankind’s greatest tool’.
Historical maps offer a unique perspective at this juncture. They have aided archaeologists in locating ancient settlements that may not be visible to us in the 21st century. One of the many unique qualities of Africa’s archaeology is that the largest constituent of her sites is of non-monumental character making it challenging even for the most robust remote sensing technologies to pick them up on the landscape. This means that archaeologists must find different means to discover and document these kinds of sites for future generations.
BIASES AND CHALLENGES
Made within the last ~200 years, historical maps can be surprisingly accurate, and can reveal information about present and past landscape changes and the societies that inhabited them. Instead of losing their value the older they become, historical maps are transformed from the current realities of their time to a document that can help reveal missing pieces of the past.
A caveat is that many historical maps are biased. The inherent contradiction of these sources of information is that while they were commonly produced and used in colonial endeavours (this part of their history should not be ignored and should be treated with utmost caution) they can also provide valuable information about regions which have been systematically understudied today. In Sudan, for example, archaeological investigations have tended to focus on the Nile Valley. This unevenness is perhaps a result of antiquarian assumptions of a one-way Egyptian influence, and the more obviously “charismatic” nature of many Nile Valley heritage sites (Meskell 2018). Darfur, on the other hand, has been chronically understudied and this has been due to such biases in conjunction with a long history of conflict in this vast region (Musa Mohamed 1986; Chlebowski and Drzewiecki 2019). The gaps however are starting to be filled. Currently, Ed Burnett at the University of Cambridge and Renier van der Merwe based at the Origins Centre in South Africa are digitising and georeferencing historical maps to enhance our understanding of the archaeology and history of eastern and southern Africa respectively.
Due to the nature of the scaling system used on these maps, a small point may, in fact, represent an area of many hundreds of meters in real life. Furthermore, different maps have different levels of accuracy, which means that a site indicated on a map may be several kilometers away from the actual site. A key factor that affects accuracy and scale of a map is where the cartographer obtained information as well as the motivation for developing the map. For example, the 1: 250,000 map series of Sudan and Zimbabwe are both the same type of maps. They are topographical in nature with the same scale. However, both have different problems and accuracy due to the different ways in which information was obtained as well as the dates in which they were created. The Sudan series is based primarily on a series of surveys in the 1900s and 1910s, and many points are incorrectly referenced making georeferencing and subsequent digitisation challenging. In contrast, the Zimbabwe series (created in the 1970’s and partially based on other maps created in the 50s and 60s) was developed from a systematic land survey with the specific function of generating an accurate topographic map, which resulted in a map series with a high degree of accuracy. Despite having high accuracy, unevenness of coverage is also a theme of many historical maps.
WORKING WITH THE DATA
Working with historical maps is by no means an easy task. The process of using historical maps, once they have been obtained in a digital format, involves three main steps: georeferencing, digitisation, and verification. Georeferencing means warping the digital historical map image into an understandable format for a GIS program, digitisation involves the plotting of points (archaeological sites) of interest into a digital format, and verification means either field-based ground truthing or the application of enhanced visual satellite imagery for site identification.
FURTHER INFORMATION
The team at MAEASaM continue to work closely with African historical maps to try to interpret past landscape uses. To explore further visit: Historical Maps – Mapping Africa’s (maeasam.org)
Contribution by:
Ed Burnett, MAEASaM Researcher for Sudan, McDonald Institute for Archaeological Research, Cambridge University.
Renier van der Merwe, MAEASaM Researcher for Zimbabwe and Botswana, Origins Centre, University of the Witwatersrand, South Africa.
References:
- Chlebowski, A., and Drzewiecki, M., 2019. Recent Research Work at the Western and Southern Fringes of Nubia. In: D. Raue (Ed.), Handbook of Ancient Nubia. Berlin: De Gruyter, pp. 1029-1049. https://doi.org/10.1515/9783110420388-042
- Meskell, L., 2018. A future in ruins: UNESCO, world heritage, and the dream of peace. New York: Oxford University Press.
- Musa Mohamed, I., 1986. The archaeology of Central Darfur (Sudan) in the 1st Millennium A.D. Oxford: B.A.R.