US A 2 PHOTOGRAMMETRIC ENGINEERING 
Two principal cameras are used in aerial photography: the nine-lens camera 
which was developed by Captain O. S. Reading; and a Wild RCS film camera. 
The former [1, 2] is especially advantageous where the coastline is irregular and 
where islands lie too far offshore to be connected to land by single-lens photog- 
raphy at a conveniently large scale, The nine-lens camera yields large scale and 
high resolution, as well as having an angular field of more than 140 degrees. 
Irregular shoreline is frequently mapped easily with the nine-lens camera where 
single-lens photography results in water models which cannot be aero-tri- 
angulated, requiring more ground control. The nine-lens camera is particularly 
useful in areas where control surveys are difficult or expensive, and at present 
it is being used mostly in Alaska where its control-saving advantages are the 
most valuable. 
The RC5 camera is used wherever single-lens aero-triangulation and com- 
pilation present no water problem and where the advantages of the nine-lens 
camera are not required. 
An older Fairchild cartographic film camera is also used as occasion de- 
mands. As the nine-lens and RC5 cameras are carried in the same airplane, 
the cartographic camera is used wherever a second airplane is utilized, espe- 
cially for chart revision purposes. 
The Division has a photographic laboratory which develops the aerial film, 
furnishes prints, enlargements, diapositives and rectifications. Aerial photog- 
raphers are employed in the laboratory during non-flying periods. The labora- 
tory equipment includes two nine-lens transforming printers, a rectifier for 
nine-lens photographs, a Saltzman enlarger, a SEG IV rectifier, a Multiplex 
diapositive printer, a LogEtronics printer, a Zeiss FE-120 film developing 
outfit, etc. The aerial film is shipped via air from the airplane to the laboratory, 
wherever the airplane might be. A sample of the film from each roll is tested 
by the aerial photographer to assure proper operation of the camera. 
It should be pointed out here that aerial photographs are usually obtained 
before field operations, as pre-marking or signalizing control stations has not yet 
become standard practice. 
The Division directs its own field parties, which fluctuate in number and size, 
and move from project to project with the seasons of the year. These photogram- 
metric field survey units establish supplemental horizontal and vertical control 
if it is required, identify the control stations on the photographs, clarify details 
on the photographs to assist the compiler, and obtain special information needed 
for nautical charts such as bridge and cable clearances and the location of aids 
to navigation. These units also field-edit completed maps where necessary, 
although all ground information is intended to be obtained by field examination 
prior to map compilation. Photogrammetric field personnel also work with 
hydrographic survey parties to supply control and inshore data for the hydro- 
graphic surveys. 
Three stationary field compilation offices, in addition to the one in the 
Washington Office, produce map manuscripts. The activities of all the field 
units, including aerial photography, are instructed and directed from an 
“Operations Branch” in the Washington Office. 
Several overlapping categories of compilation activities may seem to be 
confusing to one who is unfamiliar with the procedures. In some areas topo- 
graphic or contour maps are required, whereas in others only planimetric maps 
are needed. In some instances only a narrow fringe along the shore is required, 
whereas in other instances mapping is specified as complete to the nearest 75- 
minute line of latitude or longitude. If topographic mapping is wanted, the use 
of a stereoscopic instrument is implied; if planimetric mapping is wanted, the 
compilation may be accomplished by stereoscopic instrument or by graphic 
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