3D MODELLING OF HERITAGE SITES IN AFRICA. 
A CASE STUDY IN THE WORLD HERITAGE SITE OF KILWA KISIWANI, TANZANIA. 
Heinz Rüther 3 , Gerard Mtalo b , Eric Mngumi “.a 
3 School of Architecture, Planning and Geomatics, University of Cape Town - (Heinz.ruther@eng.uct.ac.za) 
b University College for Land and Architectural Studies, Dar es Salaam - (mtalo@uclas.ac.tz) 
CIPA 2003 XIX th International Symposium 
KEY WORDS: African Heritage, Kilwa, Digital Documentation, Laser Scanning, CAD, Data Structure 
ABSTRACT: 
No metrically correct 3D documentation exists for the UNESCO World Heritage Site of Kilwa Kisiwani and Songo Mnara, once one 
of the most important African trading centres in the Indian Ocean region. Modem technology makes it possible to create such 
documentation and develop an integrated information system for the site. This paper describes an ongoing research project on the 
documentation of two of Kilwa’s remaining structures, the fortress, known as Gereza, and the Great Mosque on Kilwa Kisiwani. The 
project forms part of the development of a methodology for the digital recording of African heritage sites and the design of a 
database as part of an integrated information system for African heritage sites. The Kilwa documentation is a pilot- and case study 
within this larger framework. It focuses on the development of appropriate methods, procedures and techniques, recognizing the 
technical, economical and physical limitations of documentation work in an African environment. Specifically, the project looks at 
the smooth transfer of photogrammetrically acquired point clouds into CAD programmes. The photogrammetry-to-CAD transfer is 
addressed through the development of a data structure, which is employed to systematically code photogrammetrically acquired 
points on features of interest. An interpreter is then used to translate the labels of the feature points and their coordinates into an 
AutoLisp feature file, which in turn can be ‘understood’ by the CAD system and plotted. The resulting 3D wireframe model forms a 
basis for the creation of surface and/or solid models that are subsequently draped with real texture for realistic representation of the 
site. The paper also reports on first experiences with a laser scanner and attempts a comparison of laser scanning and close-range 
photogrammetry. 
1. INTRODUCTION 
1.1 Back ground and motivation 
The coast of East Africa, from Mogadishu to Mozambique has 
several small offshore islands and mainland settlements with a 
history dating back to early medieval times. It is important for 
indigenous people of East Africa to realise, that the popular 
theory, that these ruins are exclusively of Arabic origin, is 
erroneous and possibly a deliberate attempt to obscure the 
predominant East African element in the history of the region. 
The structures are understood today as the relics of earlier 
Swahili settlements, and not those of foreign migrants or 
invaders (‘Arabs’, ‘Shirazi’ and others), as often maintained. 
Although the mosques and tombs are by definition Islamic, they 
are not direct transplants from Arabia or the Persian Gulf. 
Instead, their architectural style has developed locally and is 
unique to the Swahili coast in both forms and coral masonry 
techniques (J.E.G. Sutton, 1998). 
The ruins of Kilwa are the remnants of a once prominent 
trading centre in East Africa, with links to Sofala and 
Zimbabwe, to the South, and Arabia and the Far East to the 
North and East. Its merchants traded gold, silver, ivory, pearls, 
perfumes, Arabian crockery, Persian earthenware and Chinese 
porcelain. In recognition of its importance, UNESCO declared 
Kilwa a World Heritage Site in 1981 and the site also appears in 
a list of the 100 World’s Most Endangered Heritage Sites. The 
site comprises a number of buildings distributed over two 
islands, Kilwa Kisiwani and Songo Mnara. The Gereza, a 
fortress, (Figure 1) and the Great Mosque of Kilwa (Figure 2), 
two of the most prominent buildings of the site and the objects 
of the documentation, are located on Kilwa Kisiwani, in sight of 
the coast of Southern Tanzania. Ground plans of the Gereza and 
the Mosque have been published before, but no metrically 
accurate 3D documentation of the Kilwa ruins exists. It was 
therefore decided to include Kilwa into the African Heritage 
Database. 
The digital documentation of the Gereza, including 3D models, 
database and GIS is designed to 
- create a permanent digital record of the Kilwa ruins 
- provide metric data for ongoing restoration work 
- provide data for education and research 
- generate awareness of African Heritage in Africa 
- support initiatives towards the development of tourism 
- contribute to the development of an appropriate 
methodology for African heritage recording, with the aim 
of creating an African (architectural) Heritage Database and 
Information System (Rüther, 2002). 
In developing the documentation a number of factors specific to 
Kilwa and Africa had to be considered: 
- the extent of deterioration of the Gereza is such that most of 
the building has been reduced to an open structure with a 
number of freestanding walls without a roof, while about 
50% of the mosque is roofless. The top sections of the 
freestanding walls are badly broken and highly irregular