- 926 - 
The base sheet layout of 1:50,000 contained overlaps to adjoining sheets 
at most sheet edges. To avoid duplication of interpretation, and in the 
digitising which was to follow, an index map was produced delineating those 
map sheets which would include the overlapping areas (Figure 4). Grid 
coordinate values were given at each corner of the map sheet and at the 
edge of the omitted overlap section. 
Photo interpretation of the five main land-use types was undertaken, 
annotating directly onto the contact bromide prints and transferring 
Subsequently to the overlays of the 1:50,000 map sheets. This direct 
annotation facilitated checking at later stages of production. 
Linear features of less that 1 mm at publication scale (50 metres on the 
ground) were not shown because of problems which may arise in digitising 
parcels of such width. 
Administrative boundaries were traced onto the overlay from the 1:50,000 
map sheet, with reference to the 1:100,000 Administrative Area Diagrams as 
at 1st April, 1974. Included within the boundary of each local authority 
area was a four digit code with a preceding check character. Information 
regarding the coding system is available from the DOE. 
After completion of interpretation, internal and DOE checks, the output was 
passed to the drawing office for the first stage of the artwork. 
Administrative boundaries were drawn at 0.3 mm line weight and ‘developed 
areas' at 0.15 mm. These line weights were established as an aid to the 
digitising requirements. The positiolal accuracy of the plan position of 
the boundaries was to agree within 0.8 mm of its true position at publica- 
tion scale. Materials at all stages of production were of stable polyester 
base material. The interpretation overlay and artwork were drawn on matt 
positive 0.007" material, reference masters were processed onto a clear film 
positive 0.007" material (right reading), coding masters were processed onto 
an ozaloft matt positive 0.005" material being wrong reading suitable for 
the production of paper dyeline copies, and the coding overlays were processed 
onto a matt film positive 0.007" material right reading to facilitate coding. 
In all, a total of six separate artwork transparencies were produced for each 
of the 124 map sheets, each for its own particular use in coding or graphical 
output, in addition to the original interpretation overlay and artwork 
original. The photo-interpretation was completed in 12 months. 
COMPUTERISATION 
Useful as it is in mapped form, planners also need the data in statistical 
form. The manpower resources needed to measure each land-use parcel for the 
whole country and tabulate the results into meaningful aggregates manually, 
was seen to be a major problem. A pilot study indicated that the number of 
man-days likely to be involved in the handling of the data for aggregations 
would be three times that taken in the interpretation and plotting from the 
photography. It was decided to computerise the data so that the results 
could be produced quickly and manipulated more readily. 
Each land use parcel for the whole country was coded for digitising and 
computer handling and the digitised data has been used to measure the area 
of each parcel 
The computer system can produce maps showing the distribution of a single 
class of land use, or any combination of the five land uses in the data bank. 
      
  
  
  
  
  
  
   
  
  
  
   
  
  
   
  
  
  
  
  
  
   
   
   
  
   
   
  
  
  
  
  
  
  
  
    
    
  
  
  
  
  
  
  
  
  
   
    
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