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There is no doubt that studies using satellite imagery and computer compatible
tapes will provide operational techniques of analysis. The studies reported
(Thornburn, 1974) show that each of the four imagery bands may be of use and the
addition of a thermal band on Landsat 3 wil) significantly extefd the utility oft
satellite imagery for water pollution detection. Although the definition and
resolution of problem areas could be improved, it should be recognized that a new
and powerful tool has been made available.
It is generally accepted that one of the most advantageous uses of remote sensing
for environmental quality control is in its application as & surveillance tool to
detect and identify potential sources of pollution. That is, to provide the
environmental monitor with information on the proximity of hazardous materials to
waterways and on the integrity of structures designed to contain these materiels.
Most studies have found that high quality colour infra-red photography at scales
between 1/40 ,000 and 1/60 ,000 is most useful for regional surveys and coiour aerial
photography at scales of 1/5,000 to 1/10,000 is best for detailed local surveys.
4, Waste Disposal Surveys
There are many applications of remote sensing in identifying, locating, mapping
and measuring present and potential tipping sites. Just four examples are quoted
below of remote sensing applications to various aspects of waste disposal studies.
1. Standard Black and White Panchromatic Aerial Photographs - aerial photography
can provide synoptic coverage of individual waste disposal sites or for systematic
coverage of all waste disposal sites in a particular area. The type of information
that can be obtained by means of air-photo interpretation includes data on exact
size and location of waste disposal sites, whether wet or dry, hydrological
conditions in and around the site (at time of photography), nature of vegetation
cover (density, type, height etc)., whether the site is in use or disused, above
or below ground level, area of site, rock type, if any mineral is being extracted,
nunber of houses, within 1 km or distance to nearest house, number of access points,
general character of surrounding area etc, The results of such a survey can be
plotted on transparent overlays to be superimposed on available maps.
2. Colour Infra-red Photography - by using this fiim type, detailed information
on any oue site or a particular region can be obtained to examine the effects of
waste tipping on the surrounding area. The photography can be interpreted in
terms cf vegetation damage, effects that the toxic wastes may have on the ground-
water table and/or drainage and hence on the surrounding area, detailed information
on surface and sub-surface drainage conditions.
5.. Volumetric Measurements - detailed volumeiric measurements of any waste
disposal/tipping site can be obtained in order to assess the capacity of a
particular site or to examine the rate at which a site is being filled, if
repetitive measurements are taken, contoured plots of the waste disposal site,
volume computations using punched tape output from photogrammetric plotting
instruments.
4, Models - high density polyurethane land form models can be made. These can
be used for detailed planning of the site and allow monitoring of the changes to
be displayed.
5. land Degradation
In development, activities man often has a profound detrimental effect on the land.
This type of land degradation is of particular relevance in developing countries,
where the opening up of natural forests for agriculture and the activities