Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
The use of Thematic Mapper imagery for geomorphological
mapping in arid and semi-arid environments
A. R. Jones
Department of Geography, University of Reading, Berkshire, UK
ABSTRACT: The evaluation of satellite obtained imagery for geomorphological mapping is discussed with emphasis
on the main advantages of such data: a synoptic overview, multi-date coverage, multispectral imagery and dig
ital format which allows the user to employ computer-assisted image processing. The Thematic Mapper(TM) sensor
of the Landsat satellites is better suited for geoscientific applications than the earlier Multispectral scan
ner (MSS) system. This, is due to improved spatial and spectral characteristics. Examples are given, using a te;
site in southern Tunisia, of the value of TM imagery for geomorphological investigations. To effectively emplo'.
such data for such studies, digital image processing must be utilised to extract the necessary information.
Examples of techniques such as contrast stretching, image convolution, band ratioing, principal component anal
ysis and unsupervised classification are discussed.
1 INTRODUCTION
One of the numerous definitions of geomorpholgy desc
ribes it as the science of landforms. This can be ex
panded to contain reference to more than basic shape
or form,,but to include the nature of constituent or
surficial materials, mode of origin, age and process
es currently acting on the landforms. The geomorphol
ogist has to draw on knowledge from a number of wide-
ranging fields, notably geology, climatology, ecology,
pedology and hydrology and as a result, the system
atic recording of geomorphological phenomena in the
form.of a map is of great interest to a large number
of disciplines, outside of geomorphology. These range
from construction studies, civil engineering, mineral
exploration to urban planning. The aim of such a map
is to depict, in a clear and logical fashion, the nat
ure and distribution of landforms, surficial materials
and indicate the nature of the processes that lead to
the development of the landscape.
Numerous practical applications of geomorphological
mapping exist (Doornkamp et al. 1979, Panizza 1978)
not forgetting the excellent work done by ITC
(Verstappen & Zuidam 1968, Verstappen, 1972). Many
geoirorjhological mapping techniques and procedures
have been proposed through the years. Fundamental to
most of them in the utilisation of remotely sensed
images. In recent years this has, to all intents and
purposes, been confined to stereo-panchromatic aerial
photographs followed by ground observations (Perrin &
Mitchell 1969, Brunsden et al. 1979, Doornkamp et al.
1980, Verstappen 1977). However, with the development
and deployment of multispectral scanners, especially
on the Landsat Earth observation satellites, space
images have become readily available to the geomorph
ologist to study the Earth 1 s surface. McKee and Breed
(1974) used Skylab imagery to investigate sand seas,
Krinsley (1976) used Landsat data to study playas in
Iran and Mitchell & Howard (1978) used satellite imag
ery for soil degradation mapping. However, the majori
ty of satellite data used in geomorphological invest
igations have tended to be standard single band or
false colour composites. Although displaying a great
deal of geomorphological detail, much more information
can be extracted if the data is subjected to computer
assisted digital image processing. If landforms and
surficial materials can be easily extracted from pro
cessed data, then remotely sensed imagery can be used
as an effective tool for geomorphological mapping.
This paper will concentrate on illustrating the
pole that remotely sensed satellite imagery can play
in future geomorphological mapping projects by demon
strating the effectiveness of satellite Thematic Map
per imagery in monitoring geomorphological processes
and utilising suitably enhanced imagery for landform
investigation and subsequent mapping.
2 ADVANTAGES OF SATELLITE IMAGERY FOR GE0M0PH0L0GICAL
INVESTIGATIONS
The advantages of satellite imagery have been briefly
mentioned but are discussed in greater detail by
Hardy (1981). The satellite platform is an ideal stab
le base from which to obtain imagery for geomorphol
ogical investigations. The multispectral properties
of satellite scanners, in particular, the TM has been
discussed previously. This section will illustrate
the synoptic nature and the multi-date nature of sat
ellite .imagery.
Figure 1. TM4 quarter scene of southern Tunisia appr
oximately 90 x 90 kms (see text for details).
