3 which
systems (and
1ce to a large
zaluation
lation of a
in detail by
to the
use with the
e 1:120,000
orted by
S — more than
the panchromatic
ite emulsions
eys to be carried
ately, the only
d for vegetation
not available
icated that with
ems and more in
have been easier.
hite photographs,
at scale 1:40,000.
ynoptic view
itude panchromatic
aphic units such
tion of vegetation
‘cultural planning
he respective
jion types; but it
- 1411 -
is also necessary to know which kind of vegetation or present land-use already
exists on that particular site. In view of the comprehensive approach
retained for the land resources survey of Sierra Leone, it was consequently
decided to compile a reconnaissance vegetation and land-use map at the same
scale as that of the land system map. Owing to its larger scale and better
quality including resolution, the CIR photographic coverage at scale 1:10,000
was preferred to the black-and-white products at scale 1:120,000; and as
Shown in Fig. 3, IR black-and-white photographs which became available for a
Small part of the country in 1918, are Superior to panchromatic black-
and-white photographs.
Kater and Gordon (1978) deal in detail with the compilation procedure applied
and the detailed description of each of the mapping units identified and
retained for presentation at scale 1:250,000 (with a final publication scale
of 1:500,000). Table D is a summary of the legend accompanying the map,
whilst Fig. 4 provides an example of the finalised interpretation(Gordon; 1918).
The small scale CIR photographs proved to be ideally suited to the speedy
compilation of the 'reconnaissance vegetation and land-use map'. Firstly, the
relatively few photographs requiring to be handled reduced the time required
for interpretation and mapping. Secondly, the fine resolution and high colour
contrast facilitated an accurate and reliable identification and delineation of
the vegetal units. Thirdly, the fact that the entire coverage was flown during
one short season adds to the overall value of the interpretation and mapping.
At the same time, it was found that high flight CIR photographs could be
successfully used for a detailed study of vegetal types at a scale of 1:50,000
or even larger.
Other Applications
(c) Dynamic Studies
Qualitative and quantitative data about the land-use changes that occur within
Set period of time may bring about useful conclusions regarding past and
present trends. At the same time, they may assist too in the monitoring of
land-use for planning purposes.
It has been demonstrated (Schwaar 1978 a ) that HFAP and more in particular CIR
imagery at scale 1:70,000 can be successfully used for such studies. Fig. 5
illustrates the importance of 'old! photographs for mapping changes of land-use,
etc. in conjunction with new photography; and Fig. 6 provides a comparison with
information available from landsat data.
Studies of this kind cover:
- Comparative percentage and distribution of land area
under active cultivation
—~ Depletion of national forest resources
— Development rate and extent of oilpalm plantations
— Detailed studies of shifting cultivation cycles
= Movements of human settlements
— Extension and monitoring of alluvial mining activities
— Erosion development and control studies