Sniper Localization System

1

• Sniper Localization System
• Marko Gasic
• Sandeep Brar
• Ehsan Dallalzadeh
• Balraj Mattu

2
Overview

• Introduction
• Vision
• System Description
• Test Results
• Obstacles Encountered
• Project Finances
• Production Cost
• Conclusion
• Questions?

3
Introduction

• Snipers are a serious threat in urban warfare
  environment.

• Civilian threat in cases such as Washington DC
  sniper.

• Snipers are very effective at harassing and
  impeding military operations.

• AcousticShield Designs system enables
  identification of direction of origin of a sniper
  shot within seconds of the event.

4
System Overview
5
Vision

• Existing Products
• Above 15,000 US
• Available only to elite military divisions and
  not standard equipment to regular units or police
  forces

• Acoustic Shield System
• System cost around 2000
• Low cost enables local police departments and
  regular military units to purchase system

6
System Description

• Principle of Operation
• Sound waves reach 4 speakers at different times
• Using these delays we can calculate the origin of
  sound

• Functional Breakdown
• Signal Acquisition
• Gunshot Recognition
• Delay Detection
• 3-D Triangulation
• Human-Machine Interface (H.M.I)

7
Sound Acquisition

• PC Hardware
• M-Audio Delta 44 PCI audio card
• 4/4 mono analog input/output channels
• 24bit, 8kHz 96kHz independent channel sampling
• Winsound interface drivers

8
Sound Acquisition

• Microphones
• Electret Omni-directional condenser microphones.
• -45dB sensitivity
• 20Hz 16kHz Frequency Response
• 60 dB S/N ratio

9
Sound Acquisition

• Microphone Preamplifier
• Supplies minimum voltage required for microphone
  operation
• Amplifies signal to 500mV swing, compatible for
  PC soundcard input.

10
Sound Acquisition

• Software

Sample at 44kHz
Continuously sample microphone inputs
When sample exceeds 0.2V, record next 1.0 seconds
and place in memory
11
Recognition Algorithm

• Understanding the characteristic of a gun shot

12
Recognition Algorithm
Frequency Domain Representation
13
Recognition Algorithm

• Algorithm is based on comparison of average power
  between two bins

14
Recognition Algorithm

• Refinement after experimentation
• Needed to consider all 4 input at the same time

15
Recognition Algorithm

• Simple Solution
• Analyze all four microphones
• Accuracy is demonstrated in Test Results section

16
?t Extraction

• 4 similar signals, out of phase
• Use Cross Correlation to determine phase
  difference

?t14
?t13
?t12
17
3-D Triangulation

• Extrapolate origin of sound using the 3 ?ts and
  speed of sound as input

• Use Gauss-Newton method to solve 4 non linear
  equations

• Recover the X Y and Z coordinates of signal origin

• Normalize vector to give azimuth and elevation
  angles

18
User Interface

• Easy to Use/Navigate
• Targeted towards Army Personnel
• Displays Azimuth and Elevation
• No installation Required

19
Testing

• The testing was done in 2 phases
• Testing for the detection in 2-D (X,Y)
• Testing for detection of the elevation

• Procedure A
• The system was setup
• The software was running
• Located the tripod at the center of a large
  circle
• Drew a 2-D coordinate system about the center of
  the tripod
• Marked the imaginary circle around the center of
  the tripod with points each about 30 degrees
  apart
• Ran the sound sample of the gunshot twice at each
  point

20
Testing

• Recorded the Average, Trigger, X and Y values
• Took a string from the sound source(speaker) to
  the center of the tripod
• Chose a point on the string and recorded its X
  and Y components.
• At the end, had pairs of vectors in 2-D
• Comparison Stage
• Wrote a C code to input each pair of vectors to
  calculate the angle between the actual vector and
  the result vector from the system in Degrees

21
Observations

• On average, the angle difference was about 2.78
  Degrees
• The accuracy was almost the same for all the
  points in the surrounding

22
Testing cntd.

• Procedure B (Elevation)
• The system was setup
• The software was running
• Located the tripod at the center of a large
  circle
• From points 90 Degrees apart, got samples
• At each point, tried 3 different elevations
• 1) above the center plane
• 2) at the same plane
• 3) below the center plane
• Recorded the elevation that the program gave for
  each trial
• For each point, measured the elevation angle
  compared to the center of the tripod ( if above
  the center, (-) if below the center)

23
Observations

• On average, elevation difference was 3.15 Degrees
• Functional Specifications stated maximum
  allowable error of 10 degrees

24
Obstacles Encountered

• Initially used Texas Instruments DSP
• Insufficient inputs unable to sample both stereo
  codecs simultaneously
• Insufficient resolution TMSC320 C6711 main audio
  codec samples at only 11kHz, we need a minimum of
  44kHz
• Extremely poor user interface and non-existent
  (yet advertised) compatibility with MATLAB

25
Obstacles Encountered

• Initial Algorithm
• Divide sampled input into smaller intervals
• Analyze smaller intervals in frequency domain

26
Obstacles Encounterd

• Initial Algorithm
• Determine if its gun shot or not by comparing
  with known spectrum

Positive Match
27
Obstacles Encountered

• Algorithm was implemented in Matlab and Simulink

28
Obstacle Encountered

• Problems
• Unable to achieve desired speed
• Didnt do well when tried with real input
  (instead of a wave file)

29
Financial Aspects

• Prototype Development Cost
• TMSC320 Daughter Board 120.00
• MATLAB RTW Documentation 35.00
• Microphones and Pre-Amps 60.00
• Miscellaneous Audio Cables 30.00
• M-Audio Delta44 220.00
• Other 25.00
• TOTAL 490.00

30
Budget Estimate

• Initial cost estimate 2260.00
• Actual cost 490.00
• Significantly lower cost due to change in
  platform
• Savings with no loss in performance
• We were able to borrow the tripod, saving 100

31
Manufacturing Costs

• Assuming 50 units/month
• Based on Digi-Key bulk pricing where available

ITEM COST Microphone 1.20 Pre-Amp
6.00 Tripod 80.00 M-Audio Card
130.00 Cables 20.00 PC
600.00 Total 837.20
32
Conclusion

• Successfully Demonstrated Functional Concept
• Demonstrated market value and ability to produce
  at reduced cost
• Encountered problems and chose alternate
  solutions
• Stayed within budget and timeline considerations

33
Thank You

• Questions?