Radar System Engineering

108 PROPERTIES OF RADAR TARGETS [SEC, 317
overhead trolley systems often results in a concentration of particularly
bright signals along such streets. The street patterns of Chicago and
Detroit, partially visible in Figs. 3.36 and 3.37, are of this type. Some
caution is necessary in the interpretation of such displays; bright radial
lines are occasionally caused by directionally selective reflection from a
mass of buildings with parallel surfaces. Such lines appear to move along
N
FIG. 3.33.—Outer harbor, Boston, Mass. Wavelength = 1.25 cm, 0.8° beam, altitude
8000ft, radius 10nauticalmi. 42°18’N’. 70”58’W.
with the aircraft and can thus be distinguished from streets, which are
stable with respect to other signals.
3.17. Navigation. -Sections 3.12 to 3.16 have been devoted to discussions
of the kinds of targets and target contrasts encountered with
airborne radar. It remains to describe their integration into the radar
picture as a whole and the use of this picture as a navigational aid. A
fullerdiscussionof this subject will be found in vol. 2of this series.