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)