Mapping and map analysis: new tools for land evaluation

Abstract. Rural planning studies require knowledge about the attributes and spatial distributions of the natural resources of areas to be developed. When these data are available only in the form of paper maps simple technology limits the planner in the number of questions that can be answered quickly and effectively. Geographical information systems now enable mapped data to be stored and linked to other relevant spatial information so that many kinds of questions about the natural resources can be answered, and various scenarios can be compared before they are carried out. The methods used for data analysis in geographical information systems are explained briefly and are illustrated by using an example of locating a simple earth dam in a small catchment in Kisii District, Kenya. Although these new tools are often technically excellent, the results they give can be no better than the quality of the data and the models used for analysis allow. There is still much work to he done on the propagation of errors in geographical analysis, whether done with the aid of the computer or not.