Development Process
still ran rife in the process of taking aerial photographs and
converting them into cartographic data. Aerial photographs in
fact required new skills in 'reading' images for cartographic
information. Whereas aerial photographs flawlessly capture
objects directly under the focal point of the camera, they grow
increasingly oblique toward their peripheries: raised elements
bend outward from the center, whereas sunken features warp
inward.
To keep this radial distortion in check, the photography bureau
first took hundreds of overlapping photographs. Manchuria
Aviation Company teams flew their planes in a straight line,
winding back and forth, north to south, covering about 700 sq.
km per day.
While the pilot steered, the technician took photographs with a
camera mounted downwards at meticulously timed intervals,
perhaps every twenty seconds. The technician recorded the
speed, altitude, and bearing of the plane at the click of the
shutter. The pilot might have struggled to keep the aircraft on
a stable course, or misread data on faulty altimeters, though
experts could later enlarge or reduce the resulting photographs
to a common scale. Once the two had completed this phase,
they might have cross-checked their photographs by traversing
the area again, this time from east to west.
Sometimes, however, the land itself seemed to resist Japanese
efforts to document it. For example, the Sili-yin ġool desert in
Inner Mongolia held a disorienting sameness from the sky. Two
pilots there on assignment in 1937 reported that frequently they
could not figure out where they had left off the day before
because the dunes had shifted overnight, rendering the
landscape unrecognizable.
After developing the film, technicians arranged hundreds of
diachronic pictures into an overlapping pattern known as an
aerial mosaic, then reduced and traced the composite, as if to
present a synchronic surface of the earth. As this example from a
Japanese aerial photography manual shows, these unwieldy
assemblages consisted of many individual stills, each rectified
and harmonized with its neighbors. Typically, photographs
overlapped about 60 percent along the long axis of the flight
lines, and 30 percent along the sides. Cartographers then
derived elevation figures from mosaics using three-dimensional
trigonometry. Mosaics were not so much taken as produced by
technicians who edited images for tilt, blur, vibration, and scale.
As Paul Saint-Amour argues, the aerial mosaic "was anything
but free from human error. It was, rather, a delicate pas de deux
of error and counter-error." To note this process does not mean
to dismiss the accuracy of the photographs entirely; instead,
writes Saint-Amour, these imbrications suggest a contingent,
almost deceptive accuracy that lead viewers to believe in an
integrated, synchronic reality rather than a diachronic series of
pictures stitched together. Maps derived from aerial
photographs thus created a timeless representation emptied of
life forms.
