E
X A M P L E
:
T h e c on c r ete s ew er l i n e i n th e mi d d l e i s l ar g e en ou g h to l eave a s i g n atu r e f r om
b oth th e top an d th e b ottom of th e p i p e. A c l os e l ook al s o s h ow s th at th e r ad i u s of
th e s i g n atu r e i s l ar g er c omp ar ed to th e w ater p i p es to th e l ef t. T h i s i n d i c ates th at
th e ob j ec t h as a l ar g er d i ameter .
In th i s examp l e, s i g n atu r es f r om th e s i d es of th e tr en c h c an al s o b e s een . W h en a
tr en c h i s b ac kf i l l ed , c h an g es th e p r op er ti es i n th e g r ou n d - - even i f th e s ame or i -
g i n al mater i al i s u s ed - - c au s e GPR w ave r ef l ec ti on s of f th e i n ter f ac e b etw een th e
f i l l an d th e tr en c h s i d ew al l .
Note:
As the diameter of the feature increases, the reflected signature flattens. In this way, an
estimate of the relative size of the feature can be made by inspecting the radius of the hyper-
bola. The reflection from the cable on the right also have a smaller radius, confirming this phe-
nomena.
