There were several reasons why the photographs were such an 

 invaluable aid. Usually the planes flew at 150 knots, which is the 

 equivalent of 2.5 miles per minute. Thus the plane would cross an 

 ice-choked fjord in less than a minute and in that time it was up to 

 the observer to estimate the number of icebergs in that fjord. By 

 using photographs, it was possible to count the number of icebergs in 

 greater detail. From the experience of the 1949 census, it was con- 

 cluded that it was impossible for the human eye to estimate the 

 quantity of icebergs in any large concentrations such as those found 

 in West Greenland fjords when traveling at high speeds. All four 

 of the cameras were equipped with filters to enable photographs to 

 be taken through light haze. Since haze was always present in vary- 

 ing degrees on all the flights, it was felt that the use of filters enabled 

 many icebergs to be photographed that were not seen by the observers. 



Photography had been employed on the 1948 census, but the results 

 were not satisfactory. The lessons learned were incorporated in the 

 photographic plan for the 1949 census. The equipment used for the 

 1949 census consisted of two F-56 cameras with 814-inch focal length 

 in each airplane with standard F-56 roll-film magazines carrying 

 125-foot rolls of Super XX aerial film. All exposures w^ere at 1/150 

 second or better, with the greatest number being made in coastal areas. 

 Intervals were computed to allow for approximately 25 percent over- 

 lap at the bottom of tlie negative. A total of 1,823 shots were made, 

 which included blanks for identification and scenic shots as well as 

 ice census shots. None of these pictures were developed before the 

 return of the planes to the United States, so it was impossible to check 

 photographic procedures wliile tlie ice census w^as being conducted. 

 In spite of this drawback, not a single exposure was lost. 



In 1948 the mounting of the cameras w\as a serious problem. This 

 j)roblem was eliminated in 1949 by constructing lightweight all- 

 metal frames to hold the cameras in place, which would enable the 

 cameras to be held at any desired elevation and azimuth. Identifica- 

 tion of photographs in Greenland waters, the great problem of the 

 1948 census, was reduced to negligible proportions in 1949. A rigid 

 procedure coordinating the actions of the photographer with the navi- 

 gator's work was develoj)ed. The efficacy of this procedure w^as fully 

 proven in the postcensus analysis of the pictures. The conclusion 

 from this latter census was that although there were more elaborate 

 cameras and associated gear for use in aerial mapping, the simplified 

 gear developed for the 1949 census combined a maximum of utility 

 with a minimum of expense. 



Final analysis of the pictures was accomplished by drawing trans- 

 parent overlays to the same size as the finished picture upon which 

 were ruled horizontal and vertical lines to represent areas 1 mile 

 square on the photograph. Camera depression angles were so com- 



42 



