t 
ıtation 
c. Boundary differences 
The perimeters of the three enumeration districts had to be 
delineated twice, one on the grid superimposed on the B+W 
photography and one on the grid superimposed on the CIR 
photography. The same line had to be traced twice by hand which 
means that different grid cells were left out or included in 
the two cases. Such disagreements occurred along the perimeters. 
A number of 27 cases were recorded. 
2. Real Differences (B) 
a. Within groups: B+W assessed as correct and CIR as 
in error 
These were cases where the cross was representing a land use 
value "beyond doubt" on the B+W photography on a "unit" or 
"sub unit level" but the identical cross on the CIR photography 
showed a different land use. ‚In these cases the B+W had to 
be accepted as correct. No such case was recorded. 
b. Within groups: CIR assessed as correct and B+W as 
in error 
These were cases where the cross represented a land use 
value "beyond doubt" on the CIR photography on a "unit" or 
"sub unit level" according to the criteria established, but 
the identical cross on the B+W photography recorded a different 
land use. In these cases the CIR was accepted as being correct. 
A number of 370 such cases were recorded. 
c. Between groups:  B4W assessed as correct and CIR as 
in errox 
In this instance the open space units were easy to describe 
but not so easy to allocate to a particular unit in the 
notation. The results were that a misclassification occurred 
when using the CIR photography. A number of 2 such cases 
were recorded. 
d. Between groups: CIR assessed as correct and B+W as 
in error 
These are very significant differences in which the open 
space was correctly identified on the CIR and incorrectly 
identified on the B+W. A number of 31 such cases were recorded. 
e. Field check necessary 
In only two cases was it found that the type of open space 
could not be identified from either of the two types of 
photography.