- the spatial distribution of the newly built-up areas, and 
     
  
  
  
   
   
   
  
   
  
   
   
  
  
  
  
  
  
  
  
    
  
  
  
    
  
  
  
  
   
   
— the total size of the newly built-up area. 
The spatial distribution, although derived from oblique airphotos, is 
  
given fairly well by each interpreter. (See figure 1, number 1-11 and BR 
compare with the standard interpretation number 12). That is not sur- 
prising, because: 
IM 
_ every interpreter has correctly interpreted between 87% and 
96% of the newly built-up area; 
— +he incorrectly included areas cover only an area between 0% 
and 11% of the newly built-up area. Individual areas are small MA 
and scattered over the whole area. (Figure 44). 
The total size of the areas is also estimated fairly well, although PH 
the two types of error (overlooked and incorrectly included) do not 
cancel each other out. The interpreters are estimating the newly SC 
built-up area between 43 ha and 50 ha, or 46 ha + 9% (standard 
deviation 4.5%) . Compared with the 48 ha of the standard interpretation, 
this means an average underestimate of only 4% and a maximum of 10-13%. 
For most urban planning purposes, this is a negligible error. (Table 2, 
columns 5 and 6). WI 
Conclusions WO 
For the test area it is demonstrated that newly built-up areas can be 
interpreted with sufficient accuracy from 35-mm camera oblique air- 
photos with negative scales between 1:7000 and 1:22,000. 
The spatial distribution of the newly built-up areas is mapped fairly 
well, because each interpreter was plotting between 87% and 96% of the 
area correctly. 
The total area mapped as newly built-up is estimated in size to be 
between 89% and 105% of the real area, this is -11% to +5%. 
Most interpreters are slightly underestimating the size of the newly 
built-up areas, because more areas are 'overlooked' than 'incorrectly 
included'. 
The time involved in mapping newly built-up areas at map scale 1:10,000 
from 35-mm camera obliques can be estimated as 1 man-day per km2 survey 
area or 2 man-days per km2 newly built-up area. 
About three oblique airphotos have to be taken per km2 survey area. 
Further research should reveal whether these results can be expected 
for other types of areas.