Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1919-05-13
MAKING MAPS BY AIRPLANE-By Frederic j. Haskn

chief engineers asked the TWO scientists
to fly over the city OF Washington and make
a map OF it. This they did, producing by
photography q map which compared favor
ably with one made on the ground, The
general then asked them to cross another
portion OF the city in d different direction,
and to join the two maps. This severe test
was passed with notable success.
These maps made by Bagley and Moffit
were not the first maps made from the air
The air service had been taking pictures from
planes which were designed to reveal gun
emplacements and the like, and were maps
in a sense. Thy had also made mosaic
maps by taking a great many small pictures
and putting them together a child pieces
out Chinese puzzle.
Bagley and Motif improved this tedious
method in two ways. In the first place, they
used a camera with three lenses synchrOnized,
so that they could take a picture with very
wide angle. One lens Of this camera points
aght down, and the other two, in order to
get wide view, point out angles. By this
method the operator is able to take picture
of wide strip of country; but while the CEN
trail third of his picture is taken in the
horizontal, the two outer thirds are taken at
angles.
If you ever went to the movies and sat way
off at one side, that everything on the screen
appeared sadly distorted you know how the
country looks in these angle pictures 1t is
out of plumb, so to speak. But Bagley and
Motif perfected a camera for rectifying this
error, by projecting the distorted airplane
picture onto an inclined plane set at an angle
which would compensate for the angle in
the original exposure
If this explanation is not altogether clear
to you, you might visit the forthcoming eX-
hibition of the interior department at which
the Bagley-Moff1t instruments will be shown.
The chief source of error in this aerial
map-making now is due to the fact the air.
plane cannot always be placed in a perfectly
horizontal position. The result is that even
the central third of the picture is distorted,
and like the side lCtures must be corrected.
Moffit and Lieutenant w. A, Hyde of the air
service, are now making experimental flights
with a stabilized camera suspended in the
airplane and controlled by a gyroscope. The
gyroscope is operated by a small motor, and
tends, of course, to keep the camera level, no
matter what position the plane takes. If the
scientists succeed in keeping their camera in
a perfectly horizontal position by this
method, they will be able to make maps from
the air with an accuracy great as most of
there that are made upon the ground.
Nest ingenious of all the instruments used
in this work is the Stereo-cOmparator, by
which elevations can be deducted from fiat
pictures. This machine was invented by a
German for quite another purpose, and is
being experimental with by Bagley and Moi
fit in their work.
The comparator finds elevations in the
same way that human eyes find them The
relief, in the landscape before you is that you
have two eyes, which focus upon the same
thing. The angle between these two lines OF
sight is used by the brain, subconsciously, to
form an idea of the distance Of the object
looked at and of it's relation to other objects.
# you had never had but one eye, you would
see everything fiat and have no idea of per-
spective
The stereo-comparator a plies this princi-
pie, much as the familiar sterescope does, by
/ placing two prints of the picture in such a
way that you look at one with each eye,
through low powered lenses. Looking in this
way at a picture of a house, taken from an
airpiane, you are amazed to see that the
house does not look like fiat blot, as in the
picture seen by the naked eyes, but appears
to stand up from the ground as house
sholild SO far you have only a stereoscope
applied to pictures taken from above. But
the comparator includes method by which
you can measure, by moving up and down a
black line in the focal plane of the eye piece
the relative distance from top to bottom OF
that house. Thus, in the of a noun
tain range, if you know one elevation in your
picture, you can ind them all