RADIO ACOUSTIC RANGING—ADAMS 237 
drawn on the sheet from each R. A. R. station at the time the projection 
is made. 
The position of the survey ship can be plotted with a beam compass, 
by swinging distance or time arcs from the respective receiving sta- 
tions, but setting the beam compass with reference to the nearest of 
Figure 3.—An area surveyed in 1939 by radio acoustic ranging (R. A. R.), showing 
the sono-radio buoys and ordinary buoys used to control the hydrography. The 
lines of buoys were located by taut-wire traverses, but some of the outer- 
most sono-radio buoys were located by R. A. R. distances. Legend: @ ordi- 
nary survey buoy; © sono-radio buoy; A triangulation station; € sextant 
fix ; _ taut-wire measurement; _.. ___. R. A. R. distance. 
the concentric circles. The position of the ship is at the intersection of 
the arcs. Positions can also be plotted by using a special circular 
celluloid protractor. 
R. A. R. was originally adopted to control hydrographic surveys be- 
yond the visibility of shore signals or where survey buoys could not be 
used. Since its use, however, does not depend on visual observation, 
