[en] In the first part of the paper a computer-aided method for dealing with the problems of site-dependent planning is described. By means of the modular program system COPLAN complex conjunction between locally varying data can be performed rapidly and accurately with respect to spatial orientation. The system consists of data input, numerous ways of processing, and graphical representation of the results. The second part shows the application of the system to preselection of sites for thermal power plants. By means of a method analyzing its usefulness, the suitability of each point in (the German Federal State of) Baden-Wuerttemberg as a power plant site is determined. Compared with the currently used methods of preliminary site selection the present method is distinguished by area-covering calculation, the possibility of balancing up advantages and disadvantages, as well as transparency and suitability for being checked up. The paper establishes and considers criteria from the fields of operational economy, safety, ecology, and district planning. The computations are performed for different orders of preference. It is shown that there are regions of sites which are acceptable with respect to a large spectrum of object systems. (orig.)