picked out two spot heights which they had already determined and asked for 

 a check. In both cases the operator came within 1/5 foot of the previously 

 recorded reading. By the 21st of April the first set of SjlOO spot heights 

 had been completed and Hydro was proofreading the typed tables. These 

 were forwarded to ONR on May 6, 1955o The second set of 5,400 SWOP 

 numbers came into my office from Hydro. By this time they were turning 

 out work at a good rate and doing an even more accurate jobo Their esti- 

 mate was that tl'ie second batch of data was accurate to within plus or minus 

 o 5 feeto 



By the first of July Hydro had forwarded the last set of the three sets 

 of data. This also was accurate to within plus or minus ,5 feet. Thus one 

 phase of the SWOP operation came to a close. The extraction of the raw 

 data from the stereo photographs had been completed. 



The question of ■whether or not we should have Hydro contour another 

 set of photos in order to show up some of the fine structure which would be 

 eliminated from data ts-ken from spot heights alone arose at tliis time. It 

 was agreed that this should be done but at a. later date when SWOP was farther 

 along. 



It remained to analyze this data ca,refuiiy to eliminate the tilt which 

 wa^p known to be present in each model and finally to subject t?ae data to 

 analysis on an electronic computer. Our attentions were now focused to the 

 problem, of getting a firm comraitment from. DTMB concerning use of their 



UNIVAC, It looked, as if our original estim.ate of the time required for the 



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