COAST. I ARTILLERY JOURNAL, - Air Defense Artillery

UNIVERSAL MEASURING CAMERA 431
I. THEORY OF THE MEASUREMENT OF THE INITIAL VELOCITY
WITH THE UNIVERSAL MEASURING CAMERA
By the equation, V= sit, we see that in measuring the velocity V
there come into question the determination of two magnitudes the path
s and the time t pertaining to it. Both are measured by the instrument.
a. Measuring the Distance. In measurement of the distance, it is
a question of determining the path passed over by the projectile from
the photograph that has heen obtained. As soon as the location of the
camera, as well as its optical axis, is known, one can compute the photographed
length of the trajectory from the negative without the necessity
of determining or indicating the limiting terminals of this distance
A
fig. t
as is done with the Boulenge instrument. For this reason the photographic
method admits of measuring the initial velocity at every desired
angle of elevation.
With the photographic measurement of the trajectory length we
make use only of the same hypothesis that is used with the Boulenge
apparatus: we assume that the path of the projectile shown in the
photograph deviates only immaterially from a straight line within the
limits shown. In this case, taking up the computation of the projectile's
passage, one camera position is sufficient. It is necessary that the
instrument have the required fittings for measuring the angles, which