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Ti ln TSA 
  
CHECKING METHODS FOR PHOTOGRAMMETRIC MAPS 
by Dr. Gian Piero LE DIVELEC 
Director of E.L.R.A. Ltd. - Florence (Italy) 
1. Methods of checking. 
I. 1. Necessity of checking. 
We have some reasons for which, assuming equal conditions of 
accuracy and details, photogrammetric surveys are economically 
convenient. Such a convenience is, for a great part, given by the 
possibility of an organisation of work, based on a subdivision and a 
specialization, and by the possibility of doing the largest part of work 
in a laboratory rather than in the fields, in other words by the possibility 
of industrializing the topographic work. The stages of a photogramme- 
tric survey are independent, though all contribute to the final result. 
The accuracy of each step determine the final accuracy of the map, and 
therefore it is necessary to arrange in advance and check the good 
realization of each of the elementary operations in order to allow the 
industrial organisation of the execution and proceed surely towards the 
final result. 
Then we need some criterion to judge the influence of each 
operation on the final result and estimate if each operation has been 
made with sufficient care. 
Dr. P. Belfiore has suggested a method to estimate the cost of a 
certain type of map. Being the topographic map a product on which the 
burden of workmanship has a greater influence than the burden of raw 
material, the principal reason of the expense is the time spent by the 
workers to finish their work. The expenses for the wages and 
concerning the waste of the instruments are in fact proportional to the 
time. For a more and more increasing economic convenience of the