<s>
Ground-penetrating	B-Algorithm
radar	I-Algorithm
(	O
GPR	O
)	O
is	O
a	O
geophysical	O
method	O
that	O
uses	O
radar	B-Application
pulses	O
to	O
image	O
the	O
subsurface	O
.	O
</s>
<s>
This	O
nondestructive	O
method	O
uses	O
electromagnetic	O
radiation	O
in	O
the	O
microwave	O
band	O
(	O
UHF/VHF	O
frequencies	O
)	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
,	O
and	O
detects	O
the	O
reflected	O
signals	O
from	O
subsurface	O
structures	O
.	O
</s>
<s>
Optimal	O
depth	O
of	O
subsurface	O
penetration	O
is	O
achieved	O
in	O
ice	O
where	O
the	O
depth	O
of	O
penetration	O
can	O
achieve	O
several	O
thousand	O
metres	O
(	O
to	O
bedrock	B-Operating_System
in	O
Greenland	O
)	O
at	O
low	O
GPR	O
frequencies	O
.	O
</s>
<s>
Ground-penetrating	B-Algorithm
radar	I-Algorithm
antennas	O
are	O
generally	O
in	O
contact	O
with	O
the	O
ground	O
for	O
the	O
strongest	O
signal	O
strength	O
;	O
however	O
,	O
GPR	O
air-launched	O
antennas	O
can	O
be	O
used	O
above	O
the	O
ground	O
.	O
</s>
<s>
The	O
first	O
patent	O
for	O
a	O
system	O
designed	O
to	O
use	O
continuous-wave	O
radar	B-Application
to	O
locate	O
buried	O
objects	O
was	O
submitted	O
by	O
Gotthelf	O
Leimbach	O
and	O
Heinrich	O
Löwy	O
in	O
1910	O
,	O
six	O
years	O
after	O
the	O
first	O
patent	O
for	O
radar	B-Application
itself	O
(	O
patent	O
DE	O
237	O
944	O
)	O
.	O
</s>
<s>
A	O
patent	O
for	O
a	O
system	O
using	O
radar	B-Application
pulses	O
rather	O
than	O
a	O
continuous	O
wave	O
was	O
filed	O
in	O
1926	O
by	O
Dr.	O
Hülsenbeck	O
(	O
DE	O
489	O
434	O
)	O
,	O
leading	O
to	O
improved	O
depth	O
resolution	O
.	O
</s>
<s>
A	O
glacier	O
's	O
depth	O
was	O
measured	O
using	O
ground	B-Algorithm
penetrating	I-Algorithm
radar	I-Algorithm
in	O
1929	O
by	O
W	O
.	O
Stern	O
.	O
</s>
<s>
In	O
1972	O
,	O
the	O
Apollo	O
17	O
mission	O
carried	O
a	O
ground	B-Algorithm
penetrating	I-Algorithm
radar	I-Algorithm
called	O
ALSE	B-Algorithm
(	O
Apollo	B-Algorithm
Lunar	I-Algorithm
Sounder	I-Algorithm
Experiment	I-Algorithm
)	O
in	O
orbit	O
around	O
the	O
Moon	O
.	O
</s>
<s>
In	O
the	O
Earth	O
sciences	O
it	O
is	O
used	O
to	O
study	O
bedrock	B-Operating_System
,	O
soils	O
,	O
groundwater	O
,	O
and	O
ice	O
.	O
</s>
<s>
Engineering	O
applications	O
include	O
nondestructive	O
testing	O
(	O
NDT	O
)	O
of	O
structures	O
and	O
pavements	O
,	O
locating	O
buried	O
structures	O
and	O
utility	O
lines	O
,	O
and	O
studying	O
soils	O
and	O
bedrock	B-Operating_System
.	O
</s>
<s>
Borehole	O
radars	B-Application
utilizing	O
GPR	O
are	O
used	O
to	O
map	O
the	O
structures	O
from	O
a	O
borehole	O
in	O
underground	O
mining	O
applications	O
.	O
</s>
<s>
Modern	O
directional	O
borehole	O
radar	B-Application
systems	I-Application
are	O
able	O
to	O
produce	O
three-dimensional	O
images	O
from	O
measurements	O
in	O
a	O
single	O
borehole	O
.	O
</s>
<s>
One	O
of	O
the	O
other	O
main	O
applications	O
for	O
ground-penetrating	B-Algorithm
radars	I-Algorithm
is	O
for	O
locating	O
underground	O
utilities	O
.	O
</s>
<s>
Military	O
applications	O
of	O
ground-penetrating	B-Algorithm
radar	I-Algorithm
include	O
detection	O
of	O
unexploded	O
ordnance	O
and	O
detecting	O
tunnels	O
.	O
</s>
<s>
In	O
May	O
2020	O
,	O
the	O
U.S.	O
military	O
ordered	O
ground-penetrating	B-Algorithm
radar	I-Algorithm
system	O
from	O
Chemring	O
Sensors	O
and	O
Electronics	O
Systems	O
(	O
CSES	O
)	O
,	O
to	O
detect	O
improvised	O
explosive	O
devices	O
(	O
IEDs	O
)	O
buried	O
in	O
roadways	O
,	O
in	O
$200.2	O
million	O
deal	O
.	O
</s>
<s>
A	O
recent	O
novel	O
approach	O
to	O
vehicle	O
localization	O
using	O
prior	O
map	O
based	O
images	O
from	O
ground	B-Algorithm
penetrating	I-Algorithm
radar	I-Algorithm
has	O
been	O
demonstrated	O
.	O
</s>
<s>
Termed	O
"	O
Localizing	O
Ground	B-Algorithm
Penetrating	I-Algorithm
Radar	I-Algorithm
"	O
(	O
LGPR	O
)	O
,	O
centimeter	O
level	O
accuracies	O
at	O
speeds	O
up	O
to	O
100	O
km/hr	O
(	O
60	O
mph	O
)	O
have	O
been	O
demonstrated	O
.	O
</s>
<s>
This	O
technology	O
was	O
exclusively	O
licensed	O
and	O
commercialized	O
for	O
vehicle	O
safety	O
in	O
ADAS	O
and	O
Autonomous	O
Vehicle	O
positioning	O
and	O
lane-keeping	O
systems	O
by	O
and	O
marketed	O
as	O
Ground	O
Positioning	O
Radar(tm )	O
.	O
</s>
<s>
Ground	B-Algorithm
penetrating	I-Algorithm
radar	I-Algorithm
survey	I-Algorithm
is	O
one	O
method	O
used	O
in	O
archaeological	O
geophysics	O
.	O
</s>
<s>
The	O
concept	O
of	O
radar	B-Application
is	O
familiar	O
to	O
most	O
people	O
.	O
</s>
<s>
With	O
ground	B-Algorithm
penetrating	I-Algorithm
radar	I-Algorithm
,	O
the	O
radar	B-Application
signal	O
–	O
an	O
electromagnetic	O
pulse	O
–	O
is	O
directed	O
into	O
the	O
ground	O
.	O
</s>
<s>
In	O
his	O
publication	O
,	O
Interpreting	O
Ground-penetrating	B-Algorithm
Radar	I-Algorithm
for	O
Archaeology	O
,	O
Lawrence	O
Conyers	O
,	O
who	O
is	O
"	O
one	O
of	O
the	O
first	O
archaeological	O
specialists	O
in	O
GPR	O
"	O
described	O
the	O
process	O
.	O
</s>
<s>
Multiple	O
lines	O
of	O
data	O
systematically	O
collected	O
over	O
an	O
area	O
may	O
be	O
used	O
to	O
construct	O
three-dimensional	O
or	O
tomographic	B-Algorithm
images	O
.	O
</s>
<s>
Interpretation	O
of	O
radar-grams	O
is	O
generally	O
non-intuitive	O
to	O
the	O
novice	O
.	O
</s>
<s>
Radar	B-Application
is	O
sensitive	O
to	O
changes	O
in	O
material	O
composition	O
,	O
detecting	O
changes	O
requires	O
movement	O
.	O
</s>
<s>
When	O
looking	O
through	O
stationary	O
items	O
using	O
surface-penetrating	O
or	O
ground-penetrating	B-Algorithm
radar	I-Algorithm
,	O
the	O
equipment	O
needs	O
to	O
be	O
moved	O
in	O
order	O
for	O
the	O
radar	B-Application
to	O
examine	O
the	O
specified	O
area	O
by	O
looking	O
for	O
differences	O
in	O
material	O
composition	O
.	O
</s>
<s>
The	O
speed	O
at	O
which	O
a	O
radar	B-Application
signal	O
travels	O
is	O
dependent	O
upon	O
the	O
composition	O
of	O
the	O
material	O
being	O
penetrated	O
.	O
</s>
<s>
The	O
depth	O
to	O
a	O
target	O
is	O
determined	O
based	O
on	O
the	O
amount	O
of	O
time	O
it	O
takes	O
for	O
the	O
radar	B-Application
signal	O
to	O
reflect	O
back	O
to	O
the	O
unit	O
’s	O
antenna	O
.	O
</s>
<s>
Radar	B-Application
signals	O
travel	O
at	O
different	O
velocities	O
through	O
different	O
types	O
of	O
materials	O
.	O
</s>
<s>
Ground-penetrating	B-Algorithm
radar	I-Algorithm
uses	O
a	O
variety	O
of	O
technologies	O
to	O
generate	O
the	O
radar	B-Application
signal	O
:	O
these	O
are	O
impulse	O
,	O
stepped	O
frequency	O
,	O
frequency-modulated	O
continuous-wave	O
(	O
FMCW	O
)	O
,	O
and	O
noise	O
.	O
</s>
<s>
Systems	O
on	O
the	O
market	O
in	O
2009	O
also	O
use	O
Digital	B-General_Concept
signal	I-General_Concept
processing	I-General_Concept
(	O
DSP	O
)	O
to	O
process	O
the	O
data	O
during	O
survey	O
work	O
rather	O
than	O
off-line	O
.	O
</s>
<s>
This	O
holographic	O
subsurface	O
radar	B-Application
differs	O
from	O
other	O
GPR	O
types	O
in	O
that	O
it	O
records	O
plan-view	O
subsurface	O
holograms	O
.	O
</s>
<s>
Depth	O
penetration	O
of	O
this	O
kind	O
of	O
radar	B-Application
is	O
rather	O
small	O
(	O
20	O
–	O
30cm	O
)	O
,	O
but	O
lateral	O
resolution	O
is	O
enough	O
to	O
discriminate	O
different	O
types	O
of	O
landmines	O
in	O
the	O
soil	O
,	O
or	O
cavities	O
,	O
defects	O
,	O
bugging	O
devices	O
,	O
or	O
other	O
hidden	O
objects	O
in	O
walls	O
,	O
floors	O
,	O
and	O
structural	O
elements	O
.	O
</s>
<s>
In	O
Pipe-Penetrating	O
Radar	B-Application
(	O
IPPR	O
)	O
and	O
In	O
Sewer	O
GPR	O
(	O
ISGPR	O
)	O
are	O
applications	O
of	O
GPR	O
technologies	O
applied	O
in	O
non-metallic-pipes	O
where	O
the	O
signals	O
are	O
directed	O
through	O
pipe	O
and	O
conduit	O
walls	O
to	O
detect	O
pipe	O
wall	O
thickness	O
and	O
voids	O
behind	O
the	O
pipe	O
walls	O
.	O
</s>
<s>
Wall-penetrating	B-Algorithm
radar	I-Algorithm
can	O
read	O
through	O
non-metallic	O
structures	O
as	O
demonstrated	O
for	O
the	O
first	O
time	O
by	O
ASIO	O
and	O
Australian	O
Police	O
in	O
1984	O
while	O
surveying	O
an	O
ex	O
Russian	O
Embassy	O
in	O
Canberra	O
.	O
</s>
<s>
SewerVUE	O
Technology	O
,	O
an	O
advanced	O
pipe	O
condition	O
assessment	O
company	O
utilizes	O
Pipe	O
Penetrating	O
Radar	B-Application
(	O
PPR	O
)	O
as	O
an	O
in	O
pipe	O
GPR	O
application	O
to	O
see	O
remaining	O
wall	O
thickness	O
,	O
rebar	O
cover	O
,	O
delamination	O
,	O
and	O
detect	O
the	O
presence	O
of	O
voids	O
developing	O
outside	O
the	O
pipe	O
.	O
</s>
<s>
EU	O
Detect	O
Force	O
Technology	O
,	O
an	O
advanced	O
soil	O
research	O
company	O
,	O
design	O
utilizes	O
X6	O
Plus	O
Grounding	O
Radar	B-Application
(	O
XGR	O
)	O
as	O
an	O
hybrid	O
GPR	O
application	O
for	O
military	O
mine	O
detection	O
and	O
also	O
police	O
bomb	O
detection	O
.	O
</s>
<s>
The	O
"	O
Mineseeker	O
Project	O
"	O
seeks	O
to	O
design	O
a	O
system	O
to	O
determine	O
whether	O
landmines	O
are	O
present	O
in	O
areas	O
using	O
ultra	O
wideband	O
synthetic	B-Application
aperture	I-Application
radar	I-Application
units	O
mounted	O
on	O
blimps	O
.	O
</s>
