studies is not evaluated. Generally, limits of validity are not indicated and 
research findings tend to be extrapolated without criticism, while implicitly a 
validity for the USA is claimed, but not stated. Local research in other (par- 
ticularly developing) countries should be promoted to establish valid theories 
and procedures for other situations. 
The conclusion must be that remote sensor data (photographic or non- 
photographic) are not yet an operational, basic, or supplementary, standard 
input to the modern urban planning process. Aerial photographs are widely 
used on an ad hoc basis for various isolated applications. Research deals mainly 
with the glamorous satellite imagery and shows lack of interest in the conven- 
tional photographic workhorse (Rudd 1974). Demonstrated capability and 
actual use of the majority of remote sensing systems are not yet in agreement. 
Horton supports these statements when he asserts that the majority of the 
applications of remote sensing technology in urban areas have two characteristics: 
(1) the applications are quasi-experimental, in the sense that large scale and 
continuing demonstration projects utilising remote sensing methods have not 
been carried out; and (2) adjustments in interpretation techniques and data 
translation models often are necessary when applied in different cities 
(Horton 1974). Research should try to bridge the gap between potential and 
actual application of imagery, paying more attention to organisational and 
educational aspects, as well as to the very basic question of the specification 
of the information demand of urban planners and the relationship with 
alternative sources of information. 
The European Situation 
The land use pattern, both urban and rural, in Europe has a smaller scale 
and is more varied and mixed than it is in most parts of the US. That is why 
interpretation techniques developed for American cities cannot always be 
introduced in the more compact European cities, where a long historical 
development has influenced the relation between artefacts and their use. 
Perhaps it is this changing relation (the conversion of a church into a repair 
garage etc) that makes planners doubt the feasibility of surveys with aerial 
photography. But the main reason might lie else where. 
White (1971) suggests that the planning profession fails in general to exploit 
any information category fully, even those which it ranks most important. 
She also found during a survey in 1968-69 that British planners rank aerial