50 
Standard Error 
Easting * 5,4 yards 
Northing + 5.7 yards 
Height +10,5 feet 
The average number of overlaps from these tie points to the nearest control area 
was six, 
Time Factors 
The following table gives a rough estimate of the average time taken per overlap. 
The figures are only approximate and could vary in accordance with experience of the obser- 
ver and computer, 
  
  
  
Task Time per O'Lap 
in Man Days 
Preparation of diapositives for obs, 165 
Observing and Booking 40 
Preparation of obs, for UTECOM +15 
Strip Adjustment 25 
Block Adjustment „10 
Total ver overlap 495 
  
A reduction of the above times could be achieved by the use of a camera posses- 
sing better definition and distortion characteristics and a finer reseau. The use of a 
self-recording stereocomparator such as that now being produced, by Hilger and Watts would 
also increase both the speed and accuracy of the observing and would dispense with the 
necessity for a booker, From experience it is estimated that the use of such equipment 
would reduce the above time by at least 25 man days per overlap,