accepted then the argument in favour of APR control for mapping within the 
stated tolerance can hardly be disputed, taking into account the very large saving 
in time and cost over any other method. 
ACKNOWLEDGMENT 
The author is much indebted to the Federal Government of Nigeria, the 
Electricity Corporation of Nigeria, and Messrs. Balfour, Beatty for 
permission to publish this report, and to the aircrew and photogrammetric 
specialists responsible for carrying out the work, who have contributed the 
majority of the information contained in the paper. Particular mention 
should be made of Mr. K. Keir who has been in charge of the compilation and 
analysis of the results, Mr. T. Hedges who was responsible for the operation 
of the electronic equipment, Mr. E. Green who carried out the navigation of 
the aircraft, and not least Mr.R.V.Keeling the Expedition Manager who piloted 
the aircraft. 
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