KEYWORDS: Acoustics, Transceivers, Foam, Prototyping, Imaging systems, Signal processing, Interference (communication), Target detection, General packet radio service, Signal to noise ratio
A novel quasi-monostatic system operating in a side-scan synthetic aperture acoustic (SAA) imaging mode is presented. This research project's objectives are to explore the military utility of outdoor continuous sound imaging of roadside foliage and target detection. The acoustic imaging method has several military relevant advantages such as being immune to RF jamming, superior spatial resolution as compared to 0.8-2.4 GHz ground penetrating radar (GPR), capable of standoff side and forward-looking scanning, and relatively low cost, weight and size when compared to GPR technologies. The prototype system's broadband 2-17 kHz LFM chirp transceiver is mounted on a manned all-terrain vehicle. Targets are positioned within the acoustic main beam at slant ranges of two to seven meters and on surfaces such as dirt, grass, gravel and weathered asphalt and with an intervening metallic chain link fence. Acoustic image reconstructions and signature plots result in means for literal interpretation and quantifiable analyses.
The US Army is interested in technologies that will enable it to maintain the free flow of traffic along routes such as Main Supply Routes (MSRs). Mines emplaced in the road by enemy forces under cover of darkness represent a major threat to maintaining a rapid Operational Tempo (OPTEMPO) along such routes. One technique that shows promise for detecting enemy mining activity is Airborne Change Detection, which allows an operator to detect suspicious day-to-day changes in and around the road that may be indicative of enemy mining. This paper presents an Airborne Change Detection that is currently under development at the US Army Night Vision and Electronic Sensors Directorate (NVESD). The system has been tested using a longwave infrared (LWIR) sensor on a vertical take-off and landing unmanned aerial vehicle (VTOL UAV) and a midwave infrared (MWIR) sensor on a fixed wing aircraft. The system is described and results of the various tests conducted to date are presented.
This paper discusses some preliminary results of the application of simple neural networks to the problem of landmine detection in IR imagery. A large data set of IR imagery (3-5)mum) collected as part of the U.S. Army's Lightweight Airborne Multispectral Minefield Detection (LAMD) system is used as the basis for the analysis. The data set is divided into training and testing subsets then used to train and evaluate the performance of some neural networks. A single neuron perceptron is trained and evaluated using two different types of input feature. The first type of input feature is based on the raw pixel values with typical maximum vale normalization. The second type is based on the unity vector of the inputs to take advantage of the angular displacement feature of the vector [1]. A more complex, multiple neuron network is also trained and evaluated. The results are compared to determine whether the increased computational complexity of the multiple neuron network is justified in terms of improved performance.
This paper includes analysis/assessment and development of detection algorithms: (1) the assessment of detectability of surface mines using the RX algorithm implementation, which in turn, provides a first look at the limitation of the algorithm for suitable real-time implementation; (2) the development of the adaptive real-time mine detection algorithm (ARMD) based on statistical analysis of the data. The statistical analysis includes the class distribution between mines and background, the underlying distribution for mines and background based on the quantile-quantile plot. The paper also compares the quantitative performance of probability of detection (Pd) and false alarm rates (FAR) for different detection techniques for different background and mine types. This paper also presents the minefield probability of detection versus minefield false alarm rate to gauge the minefield detection performance trade-off using: (1) only mine density; and (2) mine density with pattern. This paper also demonstrates the importance of the observables that offer the class separability between mine/target and background for automatic target detection/recognition applications. Detection algorithms with high computational capability are not the 'silver bullet' for automatic target detection/recognition as commonly believed. The art of ATR is the ability to be able to pinpoint the observables that distinguish mines and background. Once the observables offer the class separability between classes are established, any simple correlation method can deliver an acceptable performance (demonstrating that highly computational methods, indeed, are wasteful and unnecessary). This paper uses the multiband and broadband data collected with the AMBER (3.5-5)mum) camera in May 2000. This data set contains about 513 (approximately 1.1 in resolution) images covering three spectral regions: 3-5)mum, 3- 4.2)mua and 4.2-5)mua. The total number of mines and the area coverage for these three spectral regions are approximately 579, and 25200m2, respectively. Note that each spectral region contains 171 images (of which 53 images contain mines with 131 large mines, and 62 small mines) covering about 8400m2. Also note that to stimulate minefields, an image containing 3 mines with a straight line pattern is defined as a minefield opportunity.
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