63 Geocarto International, Vol. 15, No. 2, June 2000 Published by Geocarto International Centre, G.P.O. Box 4122, Hong Kong. Monitoring Trends in Urban Growth and Surveying City Quarters in Ouagadougou, Burkina Faso Using SPOT-XS Steven M. de Jong Department of Environmental Sciences, Wageningen University POBox 339, 6700 AH Wageningen, The Netherlands Alain Bagre DGUT/DASU Minist ‘ ere d’Urbanisation Ouagadougou, Burkina Faso Pieter B.M. van Teeffelen Faculty of Geographical Sciences Utrecht University, The Netherlands Willem P.A. van Deursen Carthago Consultants Rotterdam, The Netherlands Abstract City planning agencies in developing countries lack important information on the generally rapid urban development which is taking place. Remote Sensing is a promising technique which provides that much needed information. A time series of four SPOT-XS images of Ouagadougou in Burkina Faso is analyzed to assess the usefulness of SPOT imagery for urban planning, and to determine the growth of Ouagadougou between 1986 and 1997. Another research objective is to examine the possibilities which SPOT images offer for the socio-economic classification of city sections. Both traditional image classification methods and a new contextual approach are applied. The latter approach aims at identifying structural patterns within the city boundaries which can be used as indicators for district function and status. Aerial photos and field surveys are utilized as ground reference data. The conclusions are that SPOT images are useful in surveying urban expansion over time but that it is difficult to identify the socio-economic function of city districts. The 20 x 20 m spatial resolution is not sufficient to bring out some of the subtle pattern differences between the city quarters. The contextual approach yielded some promising results by separating squatter areas from others but it was not capable of differentiating pre-colonial parts and old periphery sections. High resolution images of the recently launched Ikonos satellite with a pixel size of 4 x 4 m may provide a better spatial resolution for the contextual approach. Introduction Many cities in western Africa such as Ouagadougou, Abidjan and Dakar have witnessed a very rapid increase in their population in the last decade. For the city of Ouagadougou the population has grown from 475,000 to 1.8 million between 1975 to 1996 and the end to this rapid growth is not yet in sight (figure 1). Various factors account for this rapid urbanization (Leisinger & Schmitt, 1995; Kessler & Geerling, 1994): • persistent droughts over the last 25 years led to famines in the countryside and hence to massive rural-urban migration; • the younger men and women are leaving the countryside, moving to urban areas to escape from the rigid social structure of traditional rural life; • migrants expect to find jobs in the larger cities; • high, to very high, birth rates in urban areas. A part of this urban migration could be channeled into a planned settlement structure. However, a significant part of the new population settled in a haphazard way, giving rise to spontaneous, sometimes illegal, settlements without essential amenities such as drinking water, sewage disposal, electricity and roads. City planning agencies are hampered by a lack of vital information for the planning of public services and infrastructure. The agencies face the tremendous task of investing adequately in the provision of housing, infrastructure,