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As regards aerial surveys, records show that the first recorded blanket of aerial photographic
cover for mapping purpose in Africa goes as far back as 1946. There was a sharp decline in aerial
survey activities in the 1960s presumably because it was felt that available aerial photographs
were still useful for subsequent mapping purposes. Today, the situation is only dightly improved.
Some African countries, without the means and capabilities either to up-date existing maps or
prepare new ones at suitable scales, still use the old maps. An analysis of the situation in 40
countries for which data are available revealed that only 20 of these have coverage at topographic
scales 1:50,000, out of which 12 have coverage between 0—25 per cent: 19 of these have covera-
ge from 50—100 per cent, with 14 registering 75— 100 per cent and 5 between 50—75 per cent
coverage. At the scale of 1:200,000, 20 out of the 23 countries with data have a coverage of
100 per cent whilst at scale 1:250,000, 16 out of 26 (with data) have the same coverage. Most of
these maps require considerable up-dating because of their age. Enormous gaps at these planning
scales still remain to be filled if we are to derive maximum benefit from the use of maps and ge-
nerate information required for the implementation of Africa's Priority Programme for. Econo-
mic Recovery (APPER) (1986— 1990). We cannot escape the conclusion that the basic topogra-
phic maps, accurate and up-to-date for planning and development, are still deficient in most
African countries.
Madam Chairlady,
Distinguished Participants,
Ladies and Gentlemen,
Until the advent of the photographic camera and the airplane, resource information could be
acquired only by direct observation on the ground. This method is burdensome and involves
considerable time to cover any large area. From the early thirties, the primary means of gathering
geographic and resource information have been medium- and low-altitude aircraft, various types
of camera and film, and numerous other devices to facilitate photo-interpretation and map pro-
duction. However, after the Second World War, remo te sensing from spacecrafts became the stan-
dard mode for resource data collection. Through research, it was soon discovered that this off-
shoot of space science and technology has a number of advantages over the two previous modes
direct observation on the around and data acquisition by means of medium —.and low-atitude
aircraft. These advantages are noticeable in the relative reduction in costs of surveys, practicably
unlimited overview, high efficiency of data acquisition and feasibility of exploration from general
to specifics, to mention only a few..
The development of remote sensing has witnessed two revolutions since the 1970s; namely,
the launching of the landsat series of earth-observations satellites carrying advanced sensors, and
the refinement of computer technology which now permits the measurement of homogenous
areas noted on tapes carrying landsat data. Five of these satellites are known to have been launch-
ed by the National Aeronautics Space Administration (NASA). The first three, which are no lon-
ger operational, carried multispectral scanners (MSS) which initially provided resource data for
virtually all areas of the world. The succeeding landsats 4 and 5 carry advanced sensors (thematic
mappers (TM) and multispectral) which provide continuity of data compatible with .the data
from the earlier satellites. For mapping purposes, the present satellite images have certain defects
which are currently the subject of scientitic investigation by camera and sensors designers.
As science recognizes no terminal points in investigation, the developed countries are conti-
nuously conducting experiments to rectify those ‘defects with a view to improving the quality
of the satellite images for stereoscopy, higher resolution with clear definition. Notable among
these experiments are the Metric Camera (launched by the European Space Agency], Low For-
mat Camera (LFC), ERS— 1 and the Spot (by France). The era ofa new generation of satellites
has now begun as an increasing number of developed and developing countries are entering the
Ta
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