- 1408 - 
A perusal of meterological records of Sierra Leone (72,000 km“) showed the 
country to be fairly heavily cloud-prone, to have an annual rainfall ranging 
from 1,500 to 5,000 mm, and a rainy season lasting about 7/9 months according 
to the areas with a marked dry season culminating in January and/or February. 
(cf. Table A — Rainfall, see also Fig. 2). 
In addition, there are serious problems during the dry season caused by the 
occurrence of humid haze at the start and end of the dry season and by dry, 
dust laden winds (Harmattan) prevailing during the driest months. In 
combination, these factors immediately indicate the flying season as too Short 
and hence very unsatisfactory for conventional aerial photography over an 
extensive area. This is substantiated by the fact that the previous national 
aerial photographic coverage consists of eight different missions spread out 
over a time span of 14 years (1951 to 1964) (Schwaar, 1978 a). 
With this background and sources of information, the first author was able to 
recommend in 1975, high flight colour IR aerial photography with a wide angle 
lens for the national coverage of Sierra Leone and formulated in discussion 
with the co-author ad hoc technical specifications and terms of reference. 
Simlataneous panchromatic black-end-white photography with a super wide-angle 
lens was also recommended to provide a second film-filter combination and to 
ensure in case of mishap with the CIR photography that new national coverage 
would be available immediately. This precaution proved unnecessary. 
Information on the high altitude aerial photography is summarized in Table B, 
and information on the flight plan in Fig. lb. In 15 days, 99.3% of the country 
was covered by CIR photography and 99.5% by simultaneously taken panchromatic 
black-and-white photography. 
VI. RESULTS 
1. General 
In addition to the data collected and analysed in Sierra Leone, and discussed 
in the following section, high flight or very small-scale vertical aerial 
photographs have been examined for several countries by the first author. 
These include temperate and sub-tropical Australia, Eastern Canada, Central USA, 
Tanzania and Kenya. The Tanzanian and Kenya photographs were in pan black-end- 
white and were observed as suited to several types of reconnaissance mapping, 
including land-unit, broad land-use end forest cover mapping. 
In Australia, stereoscopic pairs of black-and-white panchromatic photographs 
and transparencies taken with RC-8 and RC-9 cameras at a nominal scale of about 
1:84,000 (H:7,600 m; f: 88 mm), were compared with larger scale photographs and 
with field checking in coastal Queensland and Victoria (Howard, 1970, 1971). 
These confirmed that at very small-scale, (a) broad stand classes could be 
jdentified and delineated; (b) tree species usually could not be identified; 
(c) many woody plant sub-formations could be separately delineated; (d) meaningful 
parallax measurements of stand heights could be obtained for open forest (dry 
sclerophy/forest) and woodlands and the stands could be placed in 1 m height 
classes using regression techniques; (e) based on 20%/25% stand density classes 
and adjusted stand height classes in Mount Disappointment Forest (Victoria), the 
stands could be separated into crude gross volume classes; (f) adequate control 
points could be established for photogrammetric mapping at a scale of 1:50,000 
or smaller; (g) the area covered by the photographs could be readily divided 
into lend systems and Smaller land-units (e.g. land catena, land facets). 
      
   
   
  
   
  
  
  
  
   
  
  
  
  
  
  
  
  
  
  
  
  
   
  
  
   
  
  
    
  
  
   
  
  
  
  
  
  
   
   
   
  
  
   
   
  
    
   
   
  
    
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