Transcript IEEE Region 2 SAC Presentation

Elimination of Clutter through Signal Processing
for Landmine / Ordnance Detection (ECSPLOD)

Gabriel Ford

Aniket Hirebet

Vasileios T. Nasis

Norman Butler

Advisor:
• Dr. Athina Petropulu
May 29, 2002
Nic Dunlop
What are landmines?

Buried explosive devices.

Triggered by pressure or tripwire.

Types
• Anti-personnel
• Anti-tank

Cost 3 dollars to purchase.

Cost 1000 dollars to remove.
Nic Dunlop
The Human Toll
 Over 110 million mines are
scattered across the world.
 500 people are killed or
injured every week by
triggering landmines.
 80% of the victims are
civilians.
Nic Dunlop
Why Metal Detectors Fail
 Only effective when locating
mines with substantial metal
content.
 Modern anti-personnel mines
are made of plastics and
contain dielectric explosives.
National Defense Magazine
Ground Penetrating Radar (GPR)
DeTec - EPFL

DeTec - EPFL
Ground Penetrating Radar (GPR) can detect all types of landmines,
including modern plastic mines.
Preprocessing
Detection
Classification
 Our project focuses on preprocessing to improve landmine detection.
Experimental Setup
 Ground Penetrating Radar (GPR)
data was collected by DeTeC with
a commercial SPRscan system.
DeTec - EPFL
 Mines were buried in the center
of a scanning pattern.
 Each line in the scanning pattern
represents a separate B-scan.
GPR Data: A-scans and B-scans

The received signal at any measurement
point is called an A-scan.
A-scan

A B-scan is a collection of A-scans
recorded along a scanning line.

The vertical (time) axis corresponds to
depth.
 A B-scan represents a vertical slice of
the ground.
B-scan – Composed of A-scans
The Problem: Signal Clutter

GPR images are marred by a high degree
of clutter.

For homogeneous media, the clutter varies
little over a B-scan.
 As a result, the mine signal is still
evident.
PFM-1 Mine in SAND

For non-homogeneous media, the clutter
is more random.
 In this case, the mine signal is highly
obscured.
?
PFM-1 Mine in SOIL
Signal Clutter Defined
w
 A-scan Model:
w=c+b+s+e
e
Tx
 The received signal w:
c: antenna cross-talk
b: ground bounce
s: target signal
e: measurement noise
Rx
c
b
s
 Clutter is due primarily to ground bounce and antenna cross-talk.
Clutter Reduction
 Common clutter reduction methods include:
• subtracting a signal measured in the absence of a
target
• subtracting a moving average estimate of the
background
• ensemble mean subtraction
 These procedures are ineffective for the general case
of mines buried in non-homogeneous media.
 We have developed ECSPLOD to specifically
overcome this problem
Method of Solution
 ECSPLOD extends mean
subtraction with adaptive filtering
for interference cancellation.
d = s+n
y
x = n’
Adaptive Filter
+
-
SUM
e
x = n’
x = n’
x =dn’
x= =s+n
dn’
x= =s+n
dn’
x= =s+n
dn’
x= =s+n
dn’= s+n
d = s+n
d = s+n
 ECSPLOD updates the adaptive
filter input signal to compensate for
variation in clutter properties.
Mine Response
Plastic Mine in Sand – Mean Subtraction
Raw Data
Mean Subtraction
Plastic Mine in Soil – Mean Subtraction
Raw Data
Mean Subtraction
Plastic Mine in Soil:
Moving Average Subtraction vs. ECSPLOD
MA
ECSPLOD-NLMS
ECSPLOD-KALMAN
Summary – ECSPLOD
Raw Data
Mean Subtraction
ECSPLOD - NLMS
Plastic Mine in Soil – Detection
Raw Data
Moving Average Subtraction
ECSPLOD NLMS
ECSPLOD Kalman
Detection Evaluation – ROC Curves
PFM - 1 in Soil, NLMS
Type 72 in Soil, NLMS
Economic Summary
• Out of pocket costs were under $500 (reference material and
printing costs)
• Cost in private sector summarized below:
Salaries
$ 80,400.00
Fringe Benefits
$ 11,656.80
Consulting Services
$ 11,440.00
Hardware / Software / Equipment
$
Subtotal:
$111,104.80
Overhead @ 100 %
$111,104.80
TOTAL
$222,209.60
7,608.00
Summary and Conclusions
 The Problem:
• There is a need for a reliable demining technology
• Metal detectors do not work on all types of mines
• Ground Penetrating Data is suitable for all types of mines
• But GPR is plagued with the problem of excessive signal clutter
Summary and Conclusions
 The Solution:
• Mean Subtraction only works in homogeneous media
• Moving Average Subtraction shows some improvement
• ECSPLOD utilizes Mean Subtraction followed by Adaptive Filtering
• ROCs and visual comparisons show that ECSPLOD works
Questions and Comments
ECSPLOD
Before
After
Special thanks to:
Athina
Brian
Maja
Moshe
Wayne
Petropulu
Bystrom
Kravitz
Kam
Hill