January-February - Air Defense Artillery

Relocation Without
a Plotting Board
By Major F. G. Tandy, Coast Artillery Corps
Those Coast Artillerymen who have served much
along the East coast of our United States have a mental
picture of a flat coast without a hill for miles. However,
the \-Vest coast is very precipitous, having in many
cases high bluffs rising immediately from the beach.
Often there are hills rising from several hundred to
several thousand feet within a few thousand yards of
the coast line. This condition makes a perfect ;etup for
the use of a Depression Position Finder as a part of the
range finding system. However, in using a D.P.F. we
have encountered the problem that the position of the
guns often is of necessity one thousand yards or more
distant from any position where there is sufficient height
of site to give accurate ranges with the D.P.F. This presents
a problem in relocation without the use of a plotting
board, and for this great a difference, the range difference
chart is not yery satisfactory.
In order to solye thi~ problem, ~any ideas have been
presented and tried out and as a result an instrument we
call a Range Difference Box has, like Topsy, grown up.
It is accurate, rapid, and simple. We have no difficulty
in furnishing ranges to the guns eyery ten seconds and
BOX
Index
..
1. Pieces of Xylonite
32
5" dia. Drum for Chart
Triangular block
toe - nailed on
each end.