11 
figure 2 aerial photograph with cross grid, enlarged x 2, 
original scale 1 : 10,000 and interpretation recording sheet of the 
same area, reduced to x 2.5. An extension of the existing upper 
middle class residential area with large houses compared with those 
in figure A and B. Interpretation of two land use classes: 
0 = non-residential 
1 = residential, according to the operational definition 
interpretation notes: 
1 = the terrain is walled in, but no sign of a house 
2 = building under construction, still no roof 
3 = the cross centre point is just at the edge of the building 
4 = the location of the cross centre point is difficult to see 
5 = is the building under construction? 
6 = short slope to overcome a height difference in the terrain 
In the area 89 dots are interpreted as residential; at a 
scale of 1 : 10,000 this represents 3.6 hectares. The accuracy 
depends on sampling errors (inherent to the cross grid) and 
interpretation errors.