= 1472 — 
(à) Semi Detailed Land System/Facet Surveys 
The facets constituting land systems cannot be represented at scales 1:250,000 
and smaller. They cannot be identified or delineated satisfactorily from 
black-and-white HF photographs at soale 1:120,000 but it is possible by using 
CIR photographs at scale 1:70,000 and their black-and-white by-products, 
e.g. contact prints or enlargements. 
Such high quality black-and-white enlargements at scale 1:25,000 are currently 
used in Sierra Leone for semi-detailed land resources survey based upon land 
facets. The results of these studies will be published shortly by 
Birchall et al. 
(e) Forest Surveys 
Although the high altitude aerial photography was taken primarily for the 
Land Resources Survey Project, selected CIR photographs have been examined 
for forest inventory. This preliminary evaluation indicated that the 
photographs would provide as much information as much larger-scale black-and- 
photographs, At 4X and 6X magnification, their high resolution and high image 
sharpness are advantages. Also they are superior in forest information content 
to the older black-and-white panchromatic photographs at much larger scale. 
Fig. 7 provides a sample of the CIR photography as a black-and-white print 
at contact scale and a sample of the vegetation types mapped at a scale 
of 1:50,000 (after Kater and Gordon, 1978). 
Bearing in mind that, in the moist tropics, aerial photography has a more 
restricted role than for boreal forests, due principally to the problem of 
tree species identification, the examination of stereoscopic pairs of the 
CIR photographs indicated that (a) extraction routes for logging and 
management could be readily located and planned, (b) stratification of the 
forest ahead of survey is practicable by land-units, plant sub-formations and 
stand density olasses, (c) probably a few tree species can be identified by 
their characteristic location, colour and tone, (d) in clearings observed in 
the stereo-model, information can be obtained on the stand structure, including 
the under-storeys, (e) emergents are readily observed and counted, 
(t) meaningful parellax measurements can be obtained along the edges of 
stands, (g) information is obtainable on forest degradation and shifting 
cultivation, including several classes of regeneration/regrowth, 
(f) Water Resources Inventories 
The experience gained so far in Sierra Leone, suggests that HF CIR products 
can yield a great deal of useful thematio information relating to hydrology, 
either at a national reconnaissance level or at high intensity levels 
(e.g. for the study of river basins). 
It was also observed that HFAP can assist in the identification and location 
of ground water drilling sites whenever these are influenced by structural 
and tectonic features. 
(g) Geology 
Inspection of the HFAP and particularly CIR products indicated that they can 
make a substantial contribution to the revision and upgrading of the geological 
    
  
   
   
   
    
  
  
  
   
  
    
  
   
  
  
  
  
    
  
   
  
   
  
   
   
  
   
  
  
  
  
  
  
  
  
  
  
   
  
  
  
   
   
    
   
    
   
   
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