649 - 
hr affen 
hung eines 
ive Analyse 
•h wird eine 
(stereoscopic) relief. When proceeding to lowland areas of negligible relief, 
however, the interpretation necessarily increasingly depends on the proper 
evaluation of density patterns as in such cases the relief factor loses its im- 
poitance. The same applies if theormographic and (non-stereo) radar images 
.tersuehung 
■ optischen 
rd. 
are concerned that do not permit stereoscopic analysis. The analysis of density 
patterns then becomes almost the only approach to mapping the (horizontal) dis 
tributional patterns of landform configuration. In the case of colour material, of 
course, colour tones take the place of grey tone values. 
l recent 
Density analysis for the study of terrain poses two problems, however. Firstly, 
the densities recorded result from the reflection or emission characteristics of 
the surface of the land and thus are related rather to the cover types (vegetation, 
Dments in the 
land use) than to the landforms themselves. Contrary to relief analysis that is 
Ing produced, 
Lon techniques. 
Lief and/or of 
sities or tonal 
rooted directly in landform, density analysis is only indirectly linked to landform 
and can only be considered a reliable approach to the study of terrain if the den 
sity of the vegetative or other cover can be translated in terms of landform. The 
second problem in density analysis is that imperfections in the human eye-brain 
also serve 
system do not always render a satisfactory straightforward interpretation of grey 
tones or colour patterns. "Enhanced" images with manipulated tones and colours 
. geomorphol- 
lated to land- 
have thus been introduced. Absolute density estimates are beyond our capacities 
and various methods for quantification have therefore been developed in recent 
by stereos- 
:rits. Stereos- 
years on the basis of density slicing. An example is given in section 3 of this 
paper. 
L d SLAR 
If certain directional trends exist either in the relief or in the density pattern 
of photo- 
e major ter- 
>btainable, is 
studied, their quantitative analysis may be of interest. Various methods exist 
for this purpose. An interesting mode of analyzing patterns on aerial photographs 
and other kinds of images has arisen from the introduction of optical filtering 
techniques and the study of the diffraction patterns thus produced. The concept 
Y revealed 
is have to be 
of optical filtering is from ABBE (1873) who carried out several experiments. 
The research was continued by PORTER (1906) but the first application in earth 
y and moun- 
>tics of the 
sciences is by BARBER (1949) who unraveled a complex pattern of several swell 
directions, using conventional monochromatic light. 
iitivity 
It was the advent in 1961 of the parallel beam of coherent, monochromatic, and 
e exposure 
s thus of 
in-phase light as produced by a LASER (light amplification by stimulated emission 
of radiation), however, that opened new vistas of the kinds of applications referred 
to in this paper. The equipment was devised primarily for the study of seismic 
3 in image 
f the 
sections and the earlier publications thus relate mainly to this subject (ZDANOVIC, 
1963; DOBRIN et. al. , 1965; JACKSON, 1965; SCHEEN and v. ASPEREN, 1965).