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3 Remote sensinzgsz methods for 
engineering geological mapping 
The last decades have brought an enormous development of remote sensing 
techniques (4,5,6). Bach of these techniques, however, has certain 
limitations as to the type of information they can provide and thus the 
type of investigation for which they can be applied (7). These limitations 
may be related to the following factors: 
— each of the techniques uses a specific range of wavelengths of the 
electromagnetic spectrum (6). Each of these wavelengths provides 
exclusively information about a specific property such as reflectance 
colour, temperature, roughness 
— due to differences in the techniques of data collection the various 
remote sensing techniques yield images of different scales or resolution 
and variable geometrical qualities 
— the cost of remote sensing imagery depends on flying cost (depending on 
the size and scale), cost of processing of the images (including 
rectifying). 
It appears that a critical review of the present state of remote sensing 
is needed to show potential users which techniques might be usefully 
applied for different types of investigations. 
The following chapters briefly summarize the applicability and limitations 
of remote sensing techniques for engineering geological mapping. 
Photography, multispectral scanning, thermography and radar are dealt with. 
Geophysical techniques such as seismics, airborne magnetometry, 
geo-electrical methods and sonar, which give linear information in the 
form of sections and profiles have been left out. 
4. Photography 
4.1 Introduction 
Photography applies optical systems to image information on the recording 
medium of the visible part of the electromagnetic spectrum with some 
extension into the invisible infrared and ultraviolet. Application of 
different combinations of films and filters can narrow or broaden the 
spectral range which is recorded in the form of black and white-, colour-