Difficulties occur, however, in two aspects of checking linears 
mapped from small-scale LANDSAT imagery - entirely new systems 
can be distinguished which do not necessarily correspond with 
lithological boundaries, fracture zones, etc. Further, the 
mechanism by which many linears can be determined on LANDSAT 
imagery is not clearly known. Some estimates relate for 
example to the problem of visibility of covered faults which 
nevertheless are visible as subtle markings. These may repre- 
sent zones of structural weakness or movements or remains of 
folded layers at basement level, which influence overlying 
beds. (GÜNTHER 1975; KRONBERG 1974, 1976; MÜHLFELD 1976; REUL 
1977; REUL, REE 1976) 
Research Area 
The research area - Ost Eifel (= East Eifel) lies within the 
Central Uplands of the Rhenish Massif; and is a rump hill-country 
composed of Devonian sandstones, shales and schists. It lies 
west of the Rhine, south of the Ahr River and north of the 
Moselle, within the present state of Rhineland-Palatinate. 
Research was carried out in this area during 1975, in order to 
determine what physio-geographic factors may have influenced 
prehistoric-roman-frankish settlements here. The area covered 
is indicated on Figures 1 - 4. The project was carried out in 
standard photointerpretation methodology - an overview was ob- 
tained by means of available maps and vertical aerial photo- 
graphic series; after preliminary photointerpretation field- 
work, combined with low-level overflights, was carried out in 
1975. 
It soon became apparent, that known physio-geographic factors 
- soils, height above sea-level, exposition and slope gradient - 
could not be considered singly or in combination as governing 
the choice of settlement sites in the Ost Fifel. (MARTIN 1978) 
On the other hand, photointepretation of available verticals 
showed that a great many streams are drying up in this area, 
although average rainfall runs from 600 to 800 mm per year. 
However, geological maps of the area did not indicate fault 
or fracture structures which would influence the ground water 
regieme of the area. This can be explained by the fact, that 
previous geological researches within the Rhenish Massif had 
been carried out without use of aerial and/or satellite imagery. 
( AHRENS, SCHMIDT ca. 1952; FRECHEN 1976; FUCHS 1974; Wasser- 
wirtschaftlicher Generalplan 1971) 
Relating to research done on the occurrence of maars within the 
Eifel, the supposition had been expressed that existing rivers 
had weathered into existing large-scale faults and an overview 
small-scale map showed the relation of maars to various rivers. 
(LORENZ 1973) Another extensive report on the area dismissed 
however the possibility of fault-controlled volcanic eruption 
zones within the Eifel. (FRECHEN 1976)