Spectral, shape or texture features of the detected targets are used to model the likelihood of the targets to be
potential mines in a minefield. However, some potential mines can be false alarms due to the similarity of the mine
signatures with natural and other manmade clutter signatures. Therefore, in addition to the target features, spatial
distribution of the detected targets can be used to improve the minefield detection performance. In our recently
published SPIE paper, we evaluated minefield detection performance for both patterned and unpatterned minefields
in highly cluttered environments, simultaneously using both target features and target spatial distributions that define
Markov Marked Point Process (MMPP). The results have suggested that proper exploitation of spectral/shape
features and spatial distributions can indeed contribute improved performance of patterned and unpatterned
minefield detection. Also, the ability of the algorithm to detect the minefields in highly cluttered environments
shows the robustness of the developed minefield detection algorithm based on MMPP formulation. Moreover, the
results show that the MMPP minefield detection algorithm performs significantly better than the baseline algorithm
employing spatial point process with false alarm mitigation. Since these results were based on the simulated data, it
is not clear that the MMPP detection algorithm has fully achieved its best performance. To validate its
performance, an analytical solution for the minefield detection problem will be developed, and its performance will
be compared with the performance of the simulated solution. The analytical solution for the complete minefield
detection problem is intractable due to a large number of detections and the variation of the number of detected
mines in the minefield process. Therefore, an analytical solution for a simplified detection problem will be derived,
and its minefield performance will be compared with the minefield performance obtained from the simulation in the
same MMPP framework for different clutter rates.
Spectral, shape and texture features of the detected targets are used to model the likelihood of detections to be
potential mines in a minefield. However, a large number of these potential mines can be false alarms due to the
similarity of the mine signatures with natural and other manmade clutter objects which significantly affects the
overall detection performance. In addition to the spectral features, spatial distribution of the detected targets can be
used to improve the minefield detection performance. In this paper, spectral features and spatial distributions are
used simultaneously for minefield detection. We use nearest neighbor distances of the detected targets to capture the
spatial characteristics of the minefields. We investigate the spatial distributions and evaluate minefield performance
for both patterned and scatterable minefields in a cluttered environment where the number of detected mines is many
times less than the number of false alarms. For patterned minefields, performance for minefields with different
number of rows at different mine false alarm rates is evaluated. For scatterable minefields, we evaluate the
performance of minefields where potential mines are randomly and regularly distributed. In all cases, the false
alarms are assumed to be spatially randomly distributed. The performance of the proposed detection algorithm is
compared to the baseline algorithm using extensive simulated minefield data.
A significant amount of background airborne data was collected as part of May 2005 tests for airborne minefield detection at an arid site. The locations of false alarms which occurred consistently during different runs, were identified and geo-referenced by MultiSensor Science LLC. Ground truth information, which included pictures, type qualifiers and some hyperspectral data for these identified false alarm locations, was surveyed by ERDC-WES. This collection of background data, and subsequent survey of the false alarm locations, is unique in that it is likely the first such airborne data collection with ground truthed and documented false alarm locations. A library of signatures for different sources of these false alarms was extracted in the form of image chips and organized into a self-contained database by Missouri SandT. The library contains target chips from airborne mid wave infrared (MWIR) and multispectral imaging (MSI) sensors, representing data for different days, different times of day and different altitudes. Target chips for different surface mines were also added to the database. This database of the target signatures is expected to facilitate evaluation of spectral and shape characteristics of the false alarms, to achieve better false alarm mitigation and improve mine and minefield detection for airborne applications. The aim of this paper is to review and summarize the data collection procedure used, present the currently available database of target chips and make some recommendations regarding future data collections.
In this paper we investigate how shape/spectral similarity of the mine signature and the minefield like spatial
distribution can be exploited simultaneously to improve the performance for patterned minefield detection. The
minefield decision is based on the detected targets obtained by an anomaly detector, such as the RX algorithm in the
image of a given field segment. Spectral, shape or texture features at the target locations are used to model the
likelihood of the targets to be potential mines. The spatial characteristic of the patterned minefield is captured by the
expected distribution of nearest neighbor distances of the detected mine locations. The false alarms in the minefield
are assumed to constitute a Poisson point process. The overall minefield detection problem for a given segment is
formulated as a Markov marked point process (MMPP). Minefield decision is formulated under binary hypothesis
testing using maximum log-likelihood ratio. A quadratic complexity algorithm is developed and used to maximize
the log-likelihood ratio. A procedure based on expectation maximization is evaluated for estimating unknown
parameters like mine-level probability of detection and mine-to-mine separation. The patterned minefield detection
performance under this MMPP formulation is compared to baseline algorithms using simulated data.
A significant amount of background data was collected as part of May 2005 tests at an arid site for airborne minefield
detection. An extensive library of the target chips for MSI (four bands) and MWIR sensors for false alarms and mines
was created from this data collection, as discussed in another paper in the same proceeding. In this paper we present
some results from the analysis of this background data to determine spectral and shape characteristics of different types
of false alarms. Particularly, a set of spectral features is identified that can be used for effective false alarm rejection for
the benefit of airborne minefield detection programs. A reasonable separation between vegetation and non-vegetation
(like rocks) is shown for Normalized Difference Vegetation Index (NDVI) type metrics. Also, a reasonable separation is
shown between different types of false alarms at a given time using Color Contrast feature. The spatial distribution of
different types of false alarms, as seen in available airborne background data, is also evaluated and discussed. Such
spatial analysis is of interest from the perspective of minefield level detection and analysis. The paper is concluded with
a discussion on future directions for this effort.
In a typical minefield detection problem, the minefield decision is based on the number of detected targets in a given
field segment. The detected target locations are obtained by an anomaly detector, such as the RX, using constant target
rate (CTR) or constant false alarm rate (CFAR) thresholding. Specific shape and spectral features at the detection
locations are used to assign "mineness" or "non-mineness" measures to the detections, which are further used for false
alarm mitigation (FM). The remaining detections after FM are used to assign a minefield metric based on a spatial point
process (SPP) formulation. This paper investigates how this "mineness" attribute of the detected targets can be exploited
to improve the performance of scatterable minefield detection over and above that which is possible by FM. The
distribution of the detections in the segment is formulated as a marked point process (MPP), and the minefield decision
is based on the log-likelihood ratio test of a binary hypothesis problem. An elegant, linear complexity algorithm is
developed to maximize this log-likelihood ratio. An iterative expectation maximization algorithm is used to estimate the
unknown probability of the detection of mines. The minefield detection performance, based on SPP with false alarm
mitigation and MPP formulation under both CTR and CFAR thresholding methods, is compared using thousands of
simulated minefields and background segments.
The US Army's RDECOM CERDEC Night Vision and Electronic Sensors Directorate (NVESD), Countermine
Division is evaluating the compressibility of airborne
multi-spectral imagery for mine and minefield detection
application. Of particular interest is to assess the highest image data compression rate that can be afforded without the
loss of image quality for war fighters in the loop and performance of near real time mine detection algorithm. The
JPEG-2000 compression standard is used to perform data compression. Both lossless and lossy compressions are
considered. A multi-spectral anomaly detector such as RX (Reed & Xiaoli), which is widely used as a core
algorithm baseline in airborne mine and minefield detection on different mine types, minefields, and terrains to identify
potential individual targets, is used to compare the mine detection performance. This paper presents the compression
scheme and compares detection performance results between compressed and uncompressed imagery for various level
of compressions. The compression efficiency is evaluated and its dependence upon different backgrounds and other
factors are documented and presented using multi-spectral data.
In this paper, a fast approximate version of the Kernel
RX-algorithm, termed FastKRX is presented. The original Kernel
RX-algorithm is reformulated using a spatial weighting function. In the proposed framework, a single kernel Gram matrix is defined over the entire image domain, and the detector statistics for the whole image can be obtained directly from the centered kernel Gram matrix. A methodology based on spatial-spectral clusters is presented for the fast computation of the centered kernel Gram matrix using a multivariate Taylor series approximation. Comparative detection performance on representative airborne multispectral data for both the proposed FastKRX algorithm and the RX anomaly detector is presented. Comparative computational complexity and results on speed of execution are also presented.
We present an algorithm suite, Hybrid Airborne Mine Detector (HAMD), developed for the detection of small
scatterable surface and buried mines, using multispectral airborne images. This algorithm suite is composed of a number
of components designed for specific tasks such as image segmentation based on unsupervised clustering, localized image
enhancement, generalized signature extraction and construction, and mine classification and fusion. Since both surface
and buried mines in low contrast images are difficult to detect, a new algorithm has been developed to enhance images
locally. The signature extraction component extracts different signatures based on surface or buried mines. To extract
small surface mine signatures, moment invariance (MI) is used. However, to extract buried mine signatures, thermal
variations and spatial distributions are employed. To make the system suitable for different operational environments, a
small number of general signatures are constructed and stored in the signature library. Test results based on airborne
images have shown that signatures collected can be used to detect mines placed in different environments such as
vegetation and sandy areas. For mine classification and false alarm mitigation, statistical hypothesis tests, such as
Fisher's Discriminant Ratio (FDR) test and the Kolmogorov-Smirnov (KS) test, are used.
KEYWORDS: Land mines, Target detection, Mining, Environmental sensing, Sensors, Metals, Detection and tracking algorithms, Data modeling, Data analysis, Image processing
A typical minefield detection approach is based on a sequential processing employing mine detection and false alarm
rejection followed by minefield detection. The current approach does not work robustly under different backgrounds and
environment conditions because target signature changes with time and its performance degrades in the presence of high
density of false alarms. The aim of this research will be to advance the state of the art in detection of both patterned and
unpatterned minefield in high clutter environments. The proposed method seeks to combine false alarm rejection module
and the minefield detection module of the current architecture by spatial-spectral clustering and inference module using a
Markov Marked Point Process formulation. The approach simultaneously exploits the feature characteristics of the target
signature and spatial distribution of the targets in the interrogation region. The method is based on the premise that most
minefields can be characterized by some type of distinctive spatial distribution of "similar" looking mine targets. The
minefield detection problem is formulated as a Markov Marked Point Process (MMPP) where the set of possible mine
targets is divided into a possibly overlapping mixture of targets. The likelihood of the minefield depends simultaneously
on feature characteristics of the target and their spatial distribution. A framework using "Belief Propagation" is
developed to solve the minefield inference problem based on MMPP. Preliminary investigation using simulated data
shows the efficacy of the approach.
In recent years, airborne minefield detection has increasingly been explored due to its capability for low-risk
standoff detection and quick turnaround time. Significant research efforts have focused on the detection of surface
mines and few techniques have been proposed specifically for buried mine detection. The detection performance of
current detectors, like RX, for buried mines is not satisfactory. In this paper, we explore a methodology for buried
mine detection in multi-spectral imagery, based on texture information of the target signature. A systematic
approach for the selection of co-occurrence texture features is presented. Bhattacharya coefficient is used for the
initial selection of discriminatory texture features, followed by principal feature analysis of the selected features, to
identify minimum number of features with mutually uncorrelated information. Finally, a detection method based on
unsupervised clustering of mine features in the reduced feature space, is employed for generating the test statistic for
detection. Because the proposed method is based on co-occurrence matrix features, it is largely invariant to
illumination changes in the images. Results for the proposed method are presented, which show improvement in the
detection performance vis-a-vis multi-band RX anomaly detection, and validate the proposed clustering-based detection method.
The fundamental challenges of buried mine detection arise from the fact that the mean spectral signatures of disturbed soil areas that indicate mine presence are nearly always very similar to the signatures of mixed background pixels that naturally occur in heterogeneous scenes composed of various types of soil and vegetation. In our previous work, we demonstrated that MWIR images can be used to effectively detect the buried mines. In this work, we further improve our existing method by fusing multiple buried mine classifiers. For each target chip extracted from the MWIR image, we scan it in three directions: vertical, horizontal, and diagonal to construct three feature vectors. Since each cluster center represents all pixels in its cluster, the feature vector essentially captures the most significant thermal variations of the same target chip in three directions. In order to detect the buried mines using our variable length feature vectors, we have applied Kolmogorov-Smirnov (KS) test to discriminate buried mines from background clutters. Since we design one KS-based classifier for each directional scan, for the same target chip, there will be a total of three classifiers associated with vertical, horizontal, and diagonal scans. In our system, these three classifiers are applied to the same target chip, resulting in three independent detection results, which are further fused for the refined detection. Test results using actual MWIR images have shown that our system can effectively detect the buried mines in MWIR images with low false alarm rate.
This paper presents the development of a simulation tool to facilitate the exploration and evaluation of design tradeoffs for an Unmanned Aerial Vehicle (UAV) based minefield detection system. Mine and minefield performance estimates and design tradeoffs are obtained using explicit evaluation of detection statistics simulated under different sensors, minefield layout scenarios, and mission specific constraints. The simulated mine and minefield level performance results are compared with analytical results where available. Design tradeoffs are studied in terms of different sensor and mission profile parameters such as signal to clutter ratio, target size, field-of-regard, and detection algorithms. The analytical relationship and simulated results of mine and minefield detection performance based on these parameters are presented. Different metrics for evaluating minefield performance and their influences on design tradeoffs are discussed, and suggestions are made.
Traditional landmine detection techniques are both dangerous and time consuming. Landmines can be square, round, cylindrical, or bar shaped. The casing can be metal, plastic, or wood. These characteristics make landmine detection challenging. We have developed new methods that improve the performance of both surface and buried mine detection. Our system starts with the image segmentation based on a wavelet thresholding algorithm. In this method, we estimate the thresholding value in the wavelet domain and obtain the corresponding thresholding value in the image domain via inverse discrete wavelet transform. The thresholded image retains the pixels associated with mines together with background clutter. To determine which pixels represent the mines, we apply an adaptive self-organizing maps algorithm to cluster the thresholded image. Our surface mine classifiers are based on Fourier Descriptor and Moment Invariant to explore the geometric features of surface mines shown in the MWIR images. Our buried mine classifier utilizes the cluster intensity variations. To do this, we first cluster the target chip using a 3D unsupervised clustering algorithm. We then perform horizontal scanning to build a cluster intensity variation profile which is statistically compared with the signature profiles via Kolmogorov-Smirnov hypothesis test.
The warfighter analyst in the data processing ground control station plays an integral role in airborne minefield detection system. This warfighter-in-the-loop (WIL) is expected to reduce the minefield false alarm rate by a factor of 5. In order to achieve such a significant false alarm reduction and to facilitate the development of an efficient WIL interface, it is critical to evaluate different aspects of WIL operations for airborne minefield detection. Recently, researchers at the University of Missouri-Rolla have developed a graphical user interface (HILMFgui) application using MATLAB to evaluate minefield detection performance for the operator. We conducted a series of controlled experiments with HILMFgui using ten participants. In these experiments, we video-recorded all the experiments and conducted post-experiment interviews to learn more about the usability of the interface and the cognitive processes involved in minefield detection. The effect of various factors including the availability of automatic target recognition (ATR), availability of zoom and time constraints were considered to evaluate their influence on operator performance. Qualitative results of the factors affecting the warfighter performance in the minefield detection loop are discussed. Through the qualitative data analysis, we observed two different types of participants (classified here as aggressive and cautious). We also identified three primary types of mental models: mine centric, mine-field centric, and logical placement. Those who used a primarily mine focus had a substantially higher false alarm rate than those whose mental models were more consistent with a mine-field centric or logical placement perspective.
The ability to detect buried land mines under a wide variety of environmental conditions is an important Army requirement. Both for interpreting signatures of mines and to ensure appropriate modeling of mine and background signatures, it is important to understand the phenomena that result in different signature patterns. The dynamic signatures can change quickly in time due to changing meteorological conditions and their impact on the mine, the soil, and on the mine-soil interaction. In field tests, infrared measurements of surface and near surface mines have shown anomalous concentric thermal signatures around the mine. The cause of these irregularities is not known. We conduct numerical multidimensional finite element calculations to investigate interactions between the meteorological conditions, the mine, and the nearby soil to elucidate the cause for these signatures. Both in-situ temperature measurements and model results show that thermal interactions between the mine and the soil are responsible for the signatures. The warm area around the mine in the nearby soil is predominant primarily at night. The warm ring effect is most likely to exist in dry soil and for mines whose heat capacity exceeds that of the soil, resulting in thermal dominance of the mine in the coupled mine-soil thermal regime. Wet soils are less likely to display the thermal contrast of the warm ring. Improved understanding of physical interactions between the mine and the background may facilitate improved discrimination between signatures of mines and of false alarms.
In this paper we evaluate mine level detection performance of the human operator using high resolution mid-wave infrared (MWIR) imagery and compare it with the performance of automatic target recognition (ATR) like RX detector. Previous studies have shown that the anomaly detectors like the RX detector and even more sophisticated ATR techniques fall short of the performance achieved by human analyst for mine and minefield detection. There are three main objectives of the paper. First, we seek to establish performance bounds for mine detection using a single MWIR sensor under different conditions. Second, we evaluate the conditions under which the human visual system contributes significantly over and above RX anomaly detector. Third, we seek to qualitatively study the visual processes and mental models employed by the human operators to detect mines. A graphical user interface (HILgui) was developed using MATLAB to evaluate mine level detection performance for the operator. This interface is used to conduct a series of experiments examining performance for twenty subjects. The mine images varied systematically based on the time of day the images were collected, the type of terrain and type of mines. All the experiments were video-recorded and post-experiment interviews were conducted for qualitative analysis. Both qualitative and quantitative research techniques were used to gather and analyze the data. Results from different quantitative analysis including the accuracy of mine detection, propensity of false alarms and the time taken by the operator to mark individual targets are discussed. The mental models developed by the subjects for detection of mine targets are also discussed. Limitations of the current experiments and plans for future work are discussed. It is hoped that this systematic evaluation of a human operator in airborne mine detection will help in developing new and better ATR techniques and help identify critical features required in the operator interface for the warfighter-in-the-loop (WIL) minefield detection.
Over the past several years, an enormous amount of airborne imagery consisting of various formats has been collected and will continue into the future to support airborne mine/minefield detection processes, improve algorithm development, and aid in imaging sensor development. The ground-truthing of imagery is a very essential part of the algorithm development process to help validate the detection performance of the sensor and improving algorithm techniques. The GUI (Graphical User Interface) called SemiTruth was developed using Matlab software incorporating signal processing, image processing, and statistics toolboxes to aid in ground-truthing imagery. The semi-automated ground-truthing GUI is made possible with the current data collection method, that is including UTM/GPS (Universal Transverse Mercator/Global Positioning System) coordinate measurements for the mine target and fiducial locations on the given minefield layout to support in identification of the targets on the raw imagery. This semi-automated ground-truthing effort has developed by the US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate (NVESD), Countermine Division, Airborne Application Branch with some support by the University of Missouri-Rolla.
It is practically impossible to collect an exhaustive set of minefield data for all different environment conditions, diurnal cycle, terrain conditions and minefield layouts. Such a data collection may in fact be even more expensive to ground truth, register and maintain than to acquire. This paper explores minefield synthesis using patch-based sampling of previously acquired airborne mid-wave infra-red (MWIR) images. The main idea is to synthesize a new (minefield) image by selecting appropriate small patches from the existing images and stitching them together in a consistent manner to simulate realistic imagery for different minefield scenarios. The selected patches include those from different background types, emplaced cultural clutter and different mine types. We assume a first order Markov model for the image so that the image-patch at a particular location is dependent on the characteristics of the image patch in the immediate neighborhood only. The proposed model is capable of generating any desired terrain condition (homogenous or inhomogeneous) based on a given terrain map. In addition, it supports generating different minefield layouts such as patterned or scattered minefields using mine patches from appropriate backgrounds. The paper presents representative synthesized minefield imagery and image sequences using previously collected real airborne data. Minefield image data synthesized using this procedure should be valuable in an airborne minefield detection program for evaluating most mine detection as well as minefield detection algorithms.
During May and June of 2003, the US Army Night Vision and Electronic Sensors Directorate (NVESD) and the Ohio State University (OSU) measured the thermal behavior of mines in an arid site. Thermistors were placed in contact with both surface-laid mines and native stones and monitored from before sunset until well after sundown. Measurements of local vegetation and measurements of the surrounding soil at 2.5 and 5 cm depths were also performed. A tripod-mounted MWIR sensor was used concurrently to collect high-resolution images to identify and understand the underlying phenomena. Data were collected during both clear, sunlit conditions and during an overcast day, but because of space limitations only data acquired under the (more typical) clear conditions are described here. The results contain a number of findings. First, local soil properties appear to have important implications for the apparent mine contrast. The same type of mine at locations only a few meters apart can show significantly different contrast with the native soil. Second, natural phenomena can be a significant clutter source. The temperature of vegetation can be similar to that of mines, and a small plant will occasionally produce a signature with a shape similar to that of a surface mine. Native stones are also a source of false alarms, but they tend to show somewhat less contrast. Third, at certain times, mines are best viewed with a low-elevation angle sensor. The construction of some mines causes the temperature of the side walls to be significantly different from that of the top surface at those times. Finally, disturbing the surface of desert soil through excavation, vehicle traffic or even repeated pedestrian traffic is often sufficient to produce a strong thermal signature. This fact could be used to advantage to detect buried mines in desert environments.
A differential Global Position System (DGPS) is one of the capabilities that has been used in Countermine testing and operation by the vehicular mounted mine detector system to record the locations of the detected mines. During the system's data acquisition, the DGPS may incur the measurement errors due to measurement noises and other sources of inaccuracy that result in mis-positioning of the detected mines. The position errors, however, could be reduced if the Kalman filtering algorithm is implemented in the system. To optimally reduce these errors, the fixed- interval smoother could also be used if a small interval of processing time is allowed during the countermine testing or operation via the use of standoff radar or the forward looking IR sensor. These improvements will enhance ground registration of the candidate mines. Thus, data of the same mine that have been collected from multiple sensor or from the multiple looks by a single sensor can be associated correctly. The correct data association will provide better data fusion that improves the probability of detection and the false alarm rate. Kalman filtering and fixed-interval smoothing algorithms are developed and implemented, and the results of their applications to real test data are presented.
KEYWORDS: Signal to noise ratio, Magnetism, Aluminum, Data modeling, Mining, Monte Carlo methods, Detection and tracking algorithms, Sensors, Error analysis, Metals
This paper addresses the issue of identifying conduction objects based on their response to low frequency magnetic fields -- an area of research referred to by some as magnetic singularity identification (MSI). Real time identification was carried out on several simple geometries. The low frequency transfer function of these objects was measured for both cardinal and arbitrary orientations of the magnetic field with respect to the planes of symmetry of the objects (i.e., different polarizations). Distinct negative real axis poles (singularities) associated with each object form the basis for our real-time identification algorithm. Recognizing this identification problem as one of inference form incomplete information, application of Bayes theorem leads to a generalized likelihood ratio test (GLRT) as a solution to the M-ary hypothesis testing problem of interest here. Best performance, measured through Monte Carlo simulation presented in terms of percent correct identification versus signal-to- noise ratio, was obtained with a single pole per object orientation.
Detection of mines is an important problem to the Army. A stand-off detection radar has been developed to detect mines in real time mode at stand-off distances ranging from 5 to 30 m. This active radar consists of three horn antennas, one transmitter and two receivers, carried by a moving vehicle. The transmit horn generates 36 sinusoidal carrier signals which have frequencies ranging from 0.5 to 4 GHz, in 100 MHz steps. At each frequency, the carrier signals are modulated by a train of 16 pulses having a 10 ns pulse width and a repetition rate of 3.9 MHz. These signals resonate targets including non-metallic and metallic mines and other objects. The mines and objects' return signals will be detected by the two receive antennas. The detection algorithm is used to identify an anomaly if it exists above background. Then, the discrimination algorithm is used to distinguish between mines and other objects. Finally, the location algorithm and the differential global positioning satellite system are used to mark the position of the detected mines. Test results from last year showed that some of the mines were not detected and the positions of some of the detected mines were not marked precisely enough. This resulted in missed detections and in increasing false alarm rate. Therefore, we propose to investigate Kalman filtering to improve the performance of the radar system. A preliminary study on the use of Kalman filtering algorithm for a single target tracking is provided in this paper. We believe that accurate tracking will result in accurate locating the detected target. Kalman filtering algorithm is selected for target tracking because we consider the fact that the source as well as the receivers are moving relative to the mine. This causes the delay to be also varying with time. Therefore, a dynamic algorithm such as Kalman filtering is a good technique to track the target by estimating the variable time delay.
A metallic mine detector is one of the most effective pieces of equipment for detection of mines. Their main drawback is their extremely rate of up to 100 percent, but it can also produce a high false alarm rate in many environments. The high false alarm rate reduces the usefulness of the metal detector in the field. In order to keep a high detection rate with fewer false alarms, object/mine characterization or identification must be used. Several techniques have been implemented to reduce the false alarm rate of metal detectors. They are size discrimination, target imaging, and target signatures such as dipole moment characterization. These techniques are applied for large metallic objects/mines. P.V. Czipott and D.A. Waldron each used separate techniques to characterize smaller metallic objects and some anti-personnel mines, in work supported by US Army CECOM, Night Vision and Electronic Sensors Directorate. Dr. Czipott characterized objects/mines by measuring the frequency dependence of magnetic fields caused by electric currents induced in the target. The frequency responses were measured by using a fixture incorporating a solenoid excitation coil, a receiving coil wound as a gradiometer, and a HP 4195A network/spectrum analyzer. Ms. Waldron characterized small objects with different conductivities and orientations by measuring their phase differences using a search head with one transmitter and four receiver coils and a phase-lock analyzer. We believe that target discrimination and identification are the keys to reduce false alarm rates of metallic mine detectors. Thus, we continue to analyze and characterize small metallic targets/mines using a variety of methods.
The purpose of this simulation is to compare the backscattered coefficients (or backscattered signals) among four different explosives (TNT, COMP B, TETRATOL, and PICRATOL) and two materials (STEEL and ALUMINUM). All six will be independently buried under four different sources: dry soil, and then moist soil independently covered with snow, with ice and finally with water. The four explosives were selected to represent non-metallic mines and STEEL and ALUMINUM were selected to represent metallic mines. The backscattered coefficient of a mine is calculated using the concept of pulse reflections and transmissions at junctions and pulse attenuations in the materials. A short pulse with a constant, initial voltage progresses through four junctions of different materials such as Antenna and Air, Air and Snow, Snow and Soil, and Soil and Mine with resulting pulses reflected, transmitted at these junctions and pulse attenuated in these materials. The product of the transmission ((tau) ) and reflection ((rho) ) coefficients ((tau) 1(tau) 2(tau) 3(rho) 4(tau) 3'(tau) 2'(tau) 1'), the attenuation factors (e-2(alphaairlair)e-2(alphasoillsoil)), and the initial voltage is the backscattered signal from the mine. The backscattered coefficient of the mine is the ratio of the final voltage to the initial voltage in decibel.
KEYWORDS: Target detection, Radar, Land mines, Data processing, Mining, Advanced radar, System identification, Sun, Data acquisition, Signal processing
The objective of the Advanced Mine Detection Radar Program is to demonstrate the capability of the vehicular-mounted, frequency agile radar to detect, identify and locate metallic and nonmetallic, buried and surface land mines at a stand-off distance of about 10 meters (m). This wideband, operating frequency system consists of one transmit and two receive horns, transmit and receive circuitries, an IBM-compatible computer (PC), and a Sun computer. The transmit horn generates a train of pulsed continuous-wave (CW) signals in 36 stepped operating frequencies. These frequencies are used to resonate all nonmetallic and metallic mines. At each cycle of these pulses, while the signal of the transmit horn is off, the receive horns receive the echo, the signal of soil, roots, rocks, and targets. This echo is then mixed with the two I/Q circuits to produce the in-phase and quadrature-phase signals. These signals are then low-pass filtered, amplified, and digitized signals while the PC is acquiring a new data set at the next operating frequency. At each frequency, the system noise and the clutter of the digitized signals will be reduced by the averaging and smoothing algorithms. After all 36 frequencies have been transmitted and the data preprocessed, an anomaly will be detected, located and identifies by the data processing algorithms. The results from the final field test of this program shows a 100 percent detection with an average of 36 percent identification and 17 false alarms per 78 m2 in a condition of nearly 5 percent of the moisture content in the soil.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.