) showed the
infall ranging
onths according
rd/or February.
caused by the
n and by dry,
hse In
son as too short
phy over an
evious national
ons spread out
hor was able to
th a wide angle
in discussion
f reference.
Super wide-angle
ination and to
ional coverage
SSary.
zed in Table B,
«3% of the country
en panchromatic
, and discussed
ical aerial
rst author.
nada, Central USA,
in pan black-and-
ssance mapping,
iic photographs
ial scale of about
le photographs and
1,1970, 1971).
j8es could be
be identified;
sated; (d) meaningful
pen forest (dry
1 in 7 m height
and density classes
est (Victoria), the
) adequate control
scale of 1:50,000
readily divided
and facets).
- 1409 -
Recently, several colour (panchromatic) photographs at 1:140,000 of boreal
forest in Ontario (Canada) have been examined and compared with an existing
1959 stock-map at 1:15,840. Boreal forest was chosen, since literature over
many years indicates that photo-interpretative techniques are readily used
in this type of forest.
It was observed that, in general, the photo-interpretative characteristics
of the vegetation listed above, could be observed; but 20% crown density
classes and meaningful parallax measurements of the images of trees and
Stands could not be obtained although some larger tree crowns could be
identified, Further tree species identification was very restricted although
spruces as a group could be mapped with a much higher accuracy and reliability
than as shown on the original forest stock map.
Finally, several stereo-pairs of infrared colour photographs at 1:120,000
(H: 18,460 m: 152 mm) were examined. These photographs had been taken in
July 1972 for the US maize blight study. Appraisal of the photographs
provided similar photo-interpretative information to the Canadian photographs;
but include the separation of hardwoods from conifers and a non-measurable
stereoscopic impression of stand heights. Major classes of land-use and
several arable crops were identified against field information (e.ge alfalfa/
clover, pasture, maize, soya beans/oats).
2. A Case Study (Sierra Leone)
In order to assist the Government in the implementation of its policy on
overall development of the agricultural sector in the country, the Ministry
of Agriculture and Natural Resources initiated in mid-1975, a land resources
survey project. This was financed by the United Nations Development Programme
(UNDPY and the Government, with the FAO as executing Agency.
The quantitative land potential evaluation considered for the initial phase
of the project required comprehensive inventories of the rural land resources.
It was widely accepted that such inventories can be presented conveniently in
the form of reconnaissance maps based upon land systems and their constituent
smaller land units and &t the sametime, up-to-date vegetation and land-use
maps can also play an important role in agricultural planning, Consequently,
the production of these two major types of maps was deemed necessary and action
taken accordingly (Schwaar, 1977).
(a) Land System Map
The procedure retained for the reconnaissance mapping of physical factors
required for implementing the proposed land evaluation exercise is largely
based upon a system developed by CSIRO and others in Australia and Papua-New
Guinea (e.g. Christian and Stewart, 1953 and 1974; Haantjens, 1969; Bleeker, 1970;
Howard, 1970a,b; Bleeker and Birchall, 1978) and successfully applied in other
countries of Africa (e.g. Ethiopia, Nigeria, Zambia), Near East (e.g. Jordan) and
Far Bast (e.g. Nepal).
The evaluation of these factors in terms of suitability for agricultural use
was based on the latest framework for Land Evaluation developed by FAO (1976)
adjusted to the local conditions of Sierra Leone.