Akinyemi, F.O. 
were used to depict information on land use/land covers, etc, and constituted information base on which 
impacts were assessed. The choice of 10km x 10km size of subscenes enabled the efficient application of 
image classification techniques. The analysis of landcover type from SPOT imagery is more suited to this 
sample size. (Griffiths and Wooding, 1989). A total of forty-one (41) subscenes were extracted and 
interpreted. Production of the segment map conformed to the Geographic Information System (GIS) format 
through of the Dasymetric Mapping Principle. The scale of presentation is 1:50,000 
For the identification of impacts, cross profiles of the terrain over which the transmission lines may pass was 
drawn in order to have visual bases for the proposed alignment. This led to the creation of an impact 
magnitude map. 
4 INTERPRETATION OF IMAGERIES AND OTHER RELEVANT INFORMATION 
The objective of imagery interpretation is to establish landcover classes. This provides the basis for assigning 
the indemnity class to which any categorized cover type belongs. Although traditional landscapes do not yield 
themselves to precise classification of the component landcovers, categories of land cover/land use were 
combined into complexes of mapping units. Attention was concentrated on those cover types which are of 
major ecological and social interest, e.g. built-up area (settlements); forest complexes which includes gallery 
forest, forest reserves, traditional groves, woodlands, settlements under tree cover typical of the Igbo (eastern 
Nigeria) culture; cultivated patches, burnt surfaces, eroded sandy surfaces and water bodies. From the overall 
interpretation 15 categories of land use/landcover were established whose mapping codes are explained in the 
legend below (Table 1). 
TABLE 1: COMMON LEGEND FOR THE LAND COVER/ LAND USE CLASS 
  
  
  
  
  
CODE DISCRIPTION 
S Mainly built-up compact or open 
SB Dispersed settlements and surrounding country of woodland/ shrub with scattered farm 
plots, iron stone pans 
BS Predominantly short bush , with scattered farm plots and open bare spaces 
MS Mixture of economic trees, shrubby thickets and few isolated homesteads 
  
SMB Complex combination of cultivated areas, bare soils/ burnt-up areas, with some rural 
dispersed settlements 
  
  
M Predominantly forest/bush; with scattered traditional farm plots, combination of tree 
crops and annual crops, farm huts. 
FM Mainly forest cover, with agro-forest species 
  
FMB Complex combination of trees, cultivated areas, burnt-up areas and bare space. 
  
FMS Complex combination of agro-forestry, cultural areas, dispersed settlement. 
  
B Mainly bare soils, burnt-up surfaces, eroded or marginally cultivated gravelly soils/ 
porous soils under grazing or very marginal cultivation 
  
Very shallow depression /flat surface, under dense tree/shrub cover 
  
Built-up for some kind of industrial use 
  
Eroded steep slopes in Enugu landscape 
  
Water body 
  
  
<|€|m|8lo 
Valley, gallery forests / flood plain shrub 
  
  
  
Natural colour composite imagery of SPOT X5 data was made with the result that green on the map represents 
the very active (green) vegetation. The more homogenous the green, the denser the active vegetation cover it 
represents. At the extreme end of the vegetal cover type is the category of bare soil or very scanty vegetal 
surfaces. Such areas appear in red. Other non-vegetal surfaces such as bare soils and settlements also appear 
in the range of red, purple and violet. Built-up and other infrastructural features could be separated on the 
basis of their geometric shapes (see Figure 2). 
  
30 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.