scales 1:250,000 
ctorily from 
ossible by using 
y-products , 
000 are currently 
based upon land 
ly by 
rily for the 
been examined 
that the 
scale black-and- 
on and high image 
nformation content 
larger scale. 
d-white print 
at a scale 
y has a more 
he problem of 
pairs of the 
ing and 
cation of the 
b-formations and 
identified by 
ngs observed in 
ructure, inoluding 
nted, 
e edges of 
nd shifting 
the 
F CIR products 
g to hydrology, 
y levels 
on and location 
by structural 
d that they can 
' of the geological 
map of Sierra Leone as well as for semi-detailed studies such as the one 
recently undertaken by the National Mining Company in the alluvial diamond 
mining area of Sierra Leone, 
(n) Coastal Surveys and Fisheries 
Since the new HFAP coverages of Sierra Leone cover a significant part of the 
coastal waters of the country (Fig. 1b) they contain information which could 
be easily extracted for a number of purposes, e.g. 
- Updating the existing navigational charts (e.g. revision of 
coastline features, assessment and delineation of reef 
barriers and location of rocks) 
— Evaluation of off-shore waters for fish production and 
protection 
— Studies of estuaries and marine deposits and the analysis of 
constructional and depositional processes. 
(i)  Planimetric Mapping and Topographic Map Revision 
The high altitude aerial photography at scale 1:70,000 constitutes a valuable 
source for upgrading planimetric features of existing topographic maps. At the 
same time, enlarged products can be used in town planning activities. The 
production of medium scale topographic maps has been reported feasible from 
the CIR photographs of Sierra Leone, 
Further good topographic maps of Sierra Leone exist which were produced by 
photogrammetric method using the old photographic coverage of the country. 
However, they do not reflect completely nor accurately enough the latest 
situation regarding road network and human settlements (see Fig. 8), The 
reasons for these are as follows: 
1. Individual farms and small settlements are not necessarily 
permanent, particularly in areas of prevailing shifting 
cultivation, 
2 At the same time, footpaths and motorable tracks and some 
secondary road are abandoned or downgraded while mew ones 
are developed, 
3, In and around mining areas, the road network is being 
developed and upgraded, while towns are expanding and new 
settlements created. Conversely, nearby agricultural 
activities are regressing. 
The planning of field work operations will obviously benefit from updated 
information regarding trafficability and accessibility. Consequently, the 
revision and updating of existing topographic maps at a scale of 
1: 250,000 was undertaken, For this colour infrared iransparencies were 
preferred to panchromatic black-and-white products due to their superior 
image quality, the larger scale and finer resolution, and their minimal 
planimetric distortion,