Many studies show that using synthetic data or mixed synthetic and real data might improve machine learning (ML) performance but it is difficult to draw generalizable conclusions. A contribution to this problem is the fact that the synthetic data from most vendors are improperly filtered and contain aliased (wrapped-around) high frequency information which they should not possess. Most vendors use spatial-domain, low-pass FIR filters to generate synthetic images at various ranges. Unfortunately, these FIR filters aim for interpolation with a desired frequency domain cutoff and spatial spacing (general non-integer scale factor and/or decimation). Hence, instead of a sharp cutoff at the desired low-band, they produce aliased data. This erroneous information in synthetic imagery could actually mislead an ML algorithm. In addition, most synthetic images do not account for a camera’s MTF (Modulation Transfer Function). A Fourier-based filtering can easily incorporate any MTF in the frequency domain based on Rayleigh resolution theory, properties of a camera lens and digital image properties. The spectral properties of images which are acquired with real sensors are studied and compared them with synthetic images from several vendors. We have also developed a metric that exhibits that the camera system’s MTF shows the same spectral property for real images at different ranges. The metric can help us to determine if a synthetic image generation engine violates this property and, hence, produces erroneous information.
KEYWORDS: Sensors, Spectroscopy, Digital micromirror devices, Video, Data acquisition, Reconstruction algorithms, Cameras, Hyperspectral imaging, Detection and tracking algorithms, Video compression
We present the system integration and validation tests of a compressive Multi-Mission Electro-Optical Sensor (MMEOS). With the unique algorithm implementation, the sensor exhibits exceptional agility enabling both multispectral (MS) sensing for wide area situational awareness and hyperspectral (HS) sensing for target recognition and identification. The sensor enables seamless mission changes on-the-fly via only software configuration of the operational parameters such as spatial, spectral and temporal resolutions based on mission requirements.
Conventional electro-optical and infrared (EO/IR) systems (i.e., active, passive, multiband and hyperspectral) capture an image by optically focusing the incident light at each of the millions of pixels in a focal plane array. The optics and the focal plane are designed to efficiently capture desired aspects (like spectral content, spatial resolution, depth of focus, polarization, etc.) of the scene. Computational imaging refers to image formation techniques that use digital computation to recover an image from an appropriately multiplexed or coded light intensity of the scene. In this case, the desired aspects of the scene can be selected at the time of image reconstruction which allows greater flexibility of the EO/IR system. Compressive sensing involves capturing a smaller number of specifically designed measurements from the scene to computationally recover the image or task specific scene information. Compressive sensing has the potential to acquire an image with equivalent information content to a large format array while using smaller, cheaper, and lower bandwidth components. More significantly, the data acquisition can be sequenced and designed to capture task specific and mission relevant information guided by the scene content with more flexibility. However, the benefits of compressive sensing and computational imaging do not come without compromise. NATO SET-232 has undertaken the task of investigating the promise of computational imaging and compressive sensing for EO/IR systems. This paper presents an overview of the ongoing joint activities by NATO SET-232, current computational imaging and compressive sensing technologies, limitations of the design trade space, algorithm and conceptual design considerations, and field performance assessment and modeling.
KEYWORDS: Sensors, Video, Global Positioning System, Video processing, Cameras, Telecommunications, Data acquisition, Receivers, Binary data, Data communications
Implanted mines and improvised devices are a persistent threat to Warfighters. Current Army countermine missions for route clearance need on-the-move standoff detection to improve the rate of advance. Vehicle-based forward looking sensors such as electro-optical and infrared (EO/IR) devices can be used to identify potential threats in near real-time (NRT) at safe standoff distance to support route clearance missions. The MOVERS (Micro-Cloud for Operational, Vehicle-Based EO-IR Reconnaissance System) is a vehicle-based multi-sensor integration and exploitation system that ingests and processes video and imagery data captured from forward-looking EO/IR and thermal sensors, and also generates target/feature alerts, using the Video Processing and Exploitation Framework (VPEF) “plug and play” video processing toolset. The MOVERS Framework provides an extensible, flexible, and scalable computing and multi-sensor integration GOTS framework that enables the capability to add more vehicles, sensors, processors or displays, and a service architecture that provides low-latency raw video and metadata streams as well as a command and control interface. Functionality in the framework is exposed through the MOVERS SDK which decouples the implementation of the service and client from the specific communication protocols.
The scope of the Micro-Cloud for Operational, Vehicle-Based EO-IR Reconnaissance System (MOVERS) development effort, managed by the Night Vision and Electronic Sensors Directorate (NVESD), is to develop, integrate, and demonstrate new sensor technologies and algorithms that improve improvised device/mine detection using efficient and effective exploitation and fusion of sensor data and target cues from existing and future Route Clearance Package (RCP) sensor systems. Unfortunately, the majority of forward looking Full Motion Video (FMV) and computer vision processing, exploitation, and dissemination (PED) algorithms are often developed using proprietary, incompatible software. This makes the insertion of new algorithms difficult due to the lack of standardized processing chains. In order to overcome these limitations, EOIR developed the Government off-the-shelf (GOTS) Video Processing and Exploitation Framework (VPEF) to be able to provide standardized interfaces (e.g., input/output video formats, sensor metadata, and detected objects) for exploitation software and to rapidly integrate and test computer vision algorithms. EOIR developed a vehicle-based computing framework within the MOVERS and integrated it with VPEF. VPEF was further enhanced for automated processing, detection, and publishing of detections in near real-time, thus improving the efficiency and effectiveness of RCP sensor systems.
In this paper, we present a vehicular buried threat detection approach developed over the past several years, and its latest implementation and integration in VPEF environment. Buried threats have varying signatures under different operation environment. To reliably detect the true targets and minimizing the number of false alarms, a suite of false alarm mitigators (FAMs) have been developed to process the potential targets identified by the baseline module. A vehicle track can be formed over a number of frames and targets are further analyzed both spatially and temporally. Algorithms have been implemented in C/C++ as GStreamer plugins and are suitable for vehicle mounted, on-the-move realtime exploitation.
KEYWORDS: Interference (communication), Signal detection, Signal to noise ratio, Received signal strength, Receivers, Electronic components, Antennas, Signal processing, Oscillators, Sensors
Traditional approach of locating devices relies on "tagging" with a special tracking device, for example GPS receiver.
This process of tagging is often impractical and costly since additional devices may be necessary. Conversely, in many
applications it is desired to track electronic devices, which already emit unintentional, passive radio frequency (RF)
signals. These emissions can be used to detect and locate such electronic devices. Existing schemes often rely on a priori
knowledge of the parameters of RF emission, e.g. frequency profile, and work reliably only on short distances. In
contrast, the proposed methodology aims at detecting the inherent self-similarity of the emitted RF signal by using Hurst
parameter, which (1) allows detection of unknown (not-pre-profiled) devices, (2) extends the detection range over signal
strength (peak-detection) methods, and (3) increases probability of detection over the traditional approaches. Moreover,
the distance to the device is estimated based on the Hurst parameter and passive RF signal measurements such that the
detected device can be located. Theoretical and experimental studies demonstrate improved performance of the proposed
methodology over existing ones, for instance the basic received signal strength (RSS) indicator scheme. The proposed
approach increases the detection range by 70%, the probability of detection by 60%, and improves the range estimation
and localization accuracy by 70%.
Unmanned Aerial Vehicles (UAVs) are versatile aircraft with many applications, including the potential for use to detect
unintended electromagnetic emissions from electronic devices. A particular area of recent interest has been helicopter
unmanned aerial vehicles. Because of the nature of these helicopters' dynamics, high-performance controller design for
them presents a challenge. This paper introduces an optimal controller design via output feedback control for trajectory
tracking of a helicopter UAV using a neural network (NN). The output-feedback control system utilizes the backstepping
methodology, employing kinematic, virtual, and dynamic controllers and an observer. Optimal tracking is accomplished
with a single NN utilized for cost function approximation. The controller positions the helicopter, which is equipped
with an antenna, such that the antenna can detect unintended emissions. The overall closed-loop system stability with the
proposed controller is demonstrated by using Lyapunov analysis. Finally, results are provided to demonstrate the
effectiveness of the proposed control design for positioning the helicopter for unintended emissions detection.
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.
On-board real-time processing is highly desirable in airborne detection applications. As the data processing
involved here is computationally expensive, typically high power multi-rack system is required to achieve real-time
detection. Use of such hardware on-board is often not feasible in airborne applications due to space
and power constraints. Recently, there has been a lot of interest in the use of Graphics Processing Units
(GPUs) for real-time image processing because of their highly parallel architecture, low cost, and compact
size. With the introduction of high level languages like C/CUDA (Nvidia), CTM (ATI), OpenCL, etc., GPUs
are enjoying a manifold increase in their adoption for general purpose computation. In this paper we present
GPU bound implementations of image registration and multiband RX anomaly detector. We identify the sub-problems,
namely band-to-band registration, phase correlation, feature detection, feature tracking and image
transformation, that can be efficiently parallelized on the SIMD architecture of the GPU. The results from
experiments using these implementation are compared against existing implementation written in Matlab and
C++.
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.
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-situ trace detection of explosive compounds such as RDX, TNT, and ammonium nitrate, is an important
problem for the detection of IEDs and IED precursors. Spectroscopic techniques such as LIBS and Raman have
shown promise for the detection of residues of explosive compounds on surfaces from standoff distances. Individually,
both LIBS and Raman techniques suffer from various limitations, e.g., their robustness and reliability
suffers due to variations in peak strengths and locations. However, the orthogonal nature of the spectral and
compositional information provided by these techniques makes them suitable candidates for the use of sensor
fusion to improve the overall detection performance. In this paper, we utilize peak energies in a region by fitting
Lorentzian or Gaussian peaks around the location of interest. The ratios of peak energies are used for discrimination,
in order to normalize the effect of changes in overall signal strength. Two data fusion techniques are
discussed in this paper. Multi-spot fusion is performed on a set of independent samples from the same region
based on the maximum likelihood formulation. Furthermore, the results from LIBS and Raman sensors are
fused using linear discriminators. Improved detection performance with significantly reduced false alarm rates is
reported using fusion techniques on data collected for sponsor demonstration at Fort Leonard Wood.
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.
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.
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.
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.
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.
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.
A significant amount of airborne data has been collected in the past and more is expected to be collected in the future to support airborne landmine detection research and evaluation under various programs. In order to evaluate mine and minefield detection performance for sensor and detection algorithms, it is essential to generate reliable and accurate ground truth for the location of the mine targets and fiducials present in raw imagery. The current ground truthing operation is primarily manual, which makes the ground truthing a time consuming and expensive exercise in the overall data collection effort. In this paper, a semi-automatic ground-truthing technique is presented which reduces the role of the operator to a few high-level input and validation actions. A correspondence is established between the high-contrast targets in the airborne imagery called the image features, and the known GPS locations of the targets on the ground called the map features by imposing various position and geometric constraints. These image and map features may include individual fiducial targets, rows of fiducial targets and triplets of non-collinear fiducials. The targets in the imagery are established using the RX anomaly detector. An affine or linear conformal transformation from map features to image features is calculated based on feature correspondence. This map-to-image transformation is used to generate ground-truth for mine targets. Since accurate and reliable flight-log data is currently not available, one-time specification of a few parameters like flight speed, flight direction, camera resolution and specification of the location of the initial frame on the map is required from the operator. These parameters are updated and corrected for subsequent frames based on the processing of previous frames. Image registration is used to ground-truth images which do not have enough high-contrast fiducials for reliable correspondence. A GUI called SemiAutoGT developed in MATLAB for the ground truthing process is briefly discussed. Results are presented for ground-truthing of the data collected under the Lightweight Airborne Multispectral Minefield Detection (LAMD) program.
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.
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 aim of an anomaly detector is to locate spatial target locations that show significantly different spectral/spatial characteristics as compared to the background. Typical anomaly detectors can achieve a high probability of detection, however at the cost of significantly high false alarm rates. For successful minefield detection there is a need for a further processing step to identify mine-like targets and/or reject non-mine targets in order to improve the mine detection to false alarm ratio. In this paper, we discuss a number of false alarm mitigation (FAM) modalities for MWIR imagery. In particular, we investigate measures based on circularity, gray scale shape profile and reflection symmetry. The performance of these modalities is evaluated for false alarm mitigation using real airborne MWIR data at different times of the day and for different spectral bands. We also motivate a feature based clustering and discrimination scheme based on these modalities to classify similar targets. While false alarm mitigation is primarily used to reject non-mine like targets, feature based clustering can be used to select similar-looking mine-like targets. Minefield detection can subsequently proceed on each localized cluster of similar looking targets.
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.
One of the primary lessons learned from airborne mid-wave infrared (MWIR) based mine and minefield detection research and development over the last few years has been the fact that no single algorithm or static detection architecture is able to meet mine and minefield detection performance specifications. This is true not only because of the highly varied environmental and operational conditions under which an airborne sensor is expected to perform but also due to the highly data dependent nature of sensors and algorithms employed for detection. Attempts to make the algorithms themselves more robust to varying operating conditions have only been partially successful. In this paper, we present a knowledge-based architecture to tackle this challenging problem. The detailed algorithm architecture is discussed for such a mine/minefield detection system, with a description of each functional block and data interface. This dynamic and knowledge-driven architecture will provide more robust mine and minefield detection for a highly multi-modal operating environment. The acquisition of the knowledge for this system is predominantly data driven, incorporating not only the analysis of historical airborne mine and minefield imagery data collection, but also other “all source data” that may be available such as terrain information and time of day. This “all source data” is extremely important and embodies causal information that drives the detection performance. This information is not being used by current detection architectures. Data analysis for knowledge acquisition will facilitate better understanding of the factors that affect the detection performance and will provide insight into areas for improvement for both sensors and algorithms. Important aspects of this knowledge-based architecture, its motivations and the potential gains from its implementation are discussed, and some preliminary results are presented.
Multi-band medium wave infrared (MWIR) image data collected from the Lightweight Airborne multispectral Minefield Detection-Interim (LAMD-I) program is examined for the detection of surface landmines. Because the orientation of the image acquisition from aircraft with respect to the mine and the minefield is unknown, there is a need to develop an orientation invariant-based approach for landmine and minefield detection. A rotation invariant circular harmonics transform (CHT)-based approach is presented for surface landmine detection. The magnitude information from the CHT is used for finding mine-like regions within the MWIR images. A three-tiered hierarchical thresholding technique provides the basis for highlighting potential surface landmines. Mine shape and size information are used for generating landmine confidence values. Surface landmine detection capability is presented for 82 MWIR broadband images with sand and short and long grass terrain conditions for daytime and nighttime acquired MWIR image data. Receiver operator characteristic (ROC) curves are used for comparing experimental results from this technique with an existing an adaptive multi-band CFAR detector (RX approach).
Shape features based on gray-scale moment invariants are presented for airborne mine detection and discrimination. Eleven shape features are obtained by translation, rotation and contrast normalization of the fourth-order gray-scale moments. Mahalanobis distance between an observed and true (average) shape feature vector is used as a shape metric. Covariance matrix corresponding to the average shape feature vector is obtained analytically using an additive and multiplicative noise model for the MWIR image. Effectiveness of gray scale moment invariant shape features for mine discrimination and false alarm mitigation is shown using MWIR imagery collected for LAMD-I program in May 2000. Successful implementation of the features in an airborne detection depends on the consistency of these shape features over time with change in factors such as solar illumination, ageing, clouds and environmental conditions. A study of the variability of gray-scale moment invariant-based shape features with time is conducted using MWIR time-sequenced imagery acquired in June-July 1998 by E-OIR.
In case of hand-held mine detection, the operator functions in two distinct modes. Namely the scan mode and investigation mode. In scan mode, the operator scans the area to look for potential targets. On identifying a suspect target location, the operator switches to investigation mode where he/she closely scan the area and tries to identify/discriminate target based on consistency, size and strength of the response. The aim of this paper is to look at the various aspects of sensor fusion in scan and investigation mode to fuse information from a collocated metal detector and ground penetrating radar sensors on a hand-held mine detection unit. Different sensor fusion schemes are compared. It is found that the two sensors are complimentary for a set of mine targets while they are supplementary for other set of mine targets. A better detection performance can be achieved by suitable modification to the sensor fusion scheme based on identified electromagnetic characteristics of detected targets.
Unlike Vehicle-mounted ground penetrating radar (GPR), the hand-held GPR data is highly variable. In this paper we propose an independent component analysis (ICA) based approach for processing hand held stepped frequency GPR data for mine detection. ICA is a linear transformation, which seeks prominent features in high-dimensional data. Compared to principal component analysis (PCA), which searches for basis vectors in the direction of maximum variance, ICA finds more interesting features in the direction of maximum non-gaussianity. In our current implementation, ICA is used to find a set of basis vectors corresponding to the background clutter. Residual error for this GPR with respect to ICA clutter basis shows the presence or absence of landmine. The performance of the ICA based detection is compared with the correlation detector for GPR only data for hand held mine detection. Comparative receiver operating characteristics (ROC) curves representing probability of detection verses false alarm rate are shown for both scan and investigative mode for ICA based detection and correlation detection.
The current minefield detection approach is based on a sequential processing employing mine detection followed by minefield detection. In case of patterned minefield, minefield detection algorithms seek to exploit the minefield pattern (such as linearity) while in case of scattered minefield they utilize the spatial distribution of the mine targets. However, significant challenges remain in adequate modeling and detection of the minefield process especially in the presence of false alarms due to cultured as well as natural clutter. A short review of the literature on spatial point processes is included especially for the case of scattered minefields. It is further noted that, minefields are characterized by as a pattern (or spatial distribution) of similar looking mine-like objects. The sequential mine-detection followed by mine-field detection paradigm fails to exploit this critical aspect of similarity of targets for minefield detection. In this paper we propose a minefield detection scheme that incorporates similarity based clustering of targets in order to improve the performance of minefield detection. This approach can be interpreted as statistics of a marked point process. Some preliminary comparative ROC curves are evaluated for simulated minefield data in order to show the effectiveness of the minefield detection based on the marked point process. An autonomous self-organizing scheme for on-line clustering of mine-targets is also presented.
In this paper we revisit and enhance various algorithms for landmine detection, discrimination and recognition. Single- band and multi-band medium wave infrared (MWIR) image data from the May data collection (part of Lightweight Airborne multispectral Minefield Detection-Interim (LAMBD-I) program) is used for the analysis. In particular discrimination based on gray-scale moments is explored and its effectiveness is evaluated for surface mines under IR imaging using receiver operating characteristics (ROC) curves. The discriminatory power of gray-scale moments is compared with the RX and matched fiber based detectors for different terrain (e.g., grass,sand) and different mine types. The performance of single-band (broadband) MWIR imagery is compared with multi- band (short-pass and long-pass) MWIR images. Also direct multi-band detection is compared against fusion of multiple single-band responses. Gray-scale moment based target discrimination at potential target locations, identified by RX or matched fiber detectors, is shown to be computationally efficient and provides better performance in terms of reduced false alarms for comparable probability of detection. An evolutionary framework for minefield identification, in the presence of inevitable false targets, is also presented. Starting from the locations of individual mine targets and false alarms, the evolutionary algorithm is used to identify the underlying structure of the minefield. Issues in the detection of different minefield layouts are discussed. Preliminary implementation shows the promise of this approach in identification of a wide variety of minefields.
Sensor fusion issues in a streamlined assimilation of multi-sensor information for landmine detection are discussed. In particular multi-sensor fusion in hand-held landmine detection system with ground penetrating radar (GPR) and metal detector sensors is investigated. The fusion architecture consists of feature extraction for individual sensors followed by a feed-forward neural network training to learn the feature space representation of the mine/no-mine classification. A correlation feature from GPR, and slope and energy feature from metal detector are used for discrimination. Various fusion strategies are discussed and results compared against each other and against individual sensors using ROC curves for the available multi-sensor data. Both feature level and decision level fusion have been investigated. Simple decision level fusion scheme based on Dempster-Shafer evidence accumulation, soft AND, MIN and MAX are compared. Feature level fusion using neural network training is shown to provide best results. However comparable performance is achieved using decision level sensor fusion based on Dempster-Shafer accumulation. It is noted that, the above simple feed-forward fusion scheme lacks a means to verify detections after a decision has been made. New detection algorithms that are more than anomaly detectors are needed. Preliminary results with features based on independent component analysis (ICA) show promising results towards this end.
In this paper, an architecture for multisensor data fusion and evidence accumulation for landmine detection and discrimination is presented. Evidential and discriminatory information about the buried object such as shape, size, depth, and material, chemical or electromagnetic properties is obtained from different sensor and sensor algorithms. A streamlined assimilation of these varied information from dissimilar and non-homogenous sensor and sensor algorithms is presented. Information theory based pre-processing of the data and subsequent unsupervised clustering using Dignet architecture is used to capture the underlying structure of the information available from different sensors. Sensor information is categorized into type, size, depth, and position data channels. Each sensor may provide one or more of this information. Type data channel provides any relevant discriminatory characteristics of the buried object. A supervised feed-forward neural network is used to learn the causality between the cluster information and the evidence of a given class of the buried object. Size, depth and phenomenology input are used as control gating input for the neural network mapping. The supervisory feedback is provided by the output of the global sensor fusion system and accommodates both autonomous and human assisted learning. Dempster-Shafer evidential reasoning is used to accumulate different evidence from sensor channels and thus to detect and discriminate between different types of buried landmine and clutter. Performance of fusion architecture and Dempster-Shafer reasoning is studied using simulated data. For the simulated data noisy images of regular and irregular shapes of different objects are produced. Fourier descriptor, moment invariant and Matlab shape features are used to define the shape information of the objects. Evidence accumulation is done using shape and size information form each of the algorithms.
KEYWORDS: Neurons, Land mines, Sensors, Data processing, Machine learning, Signal to noise ratio, Sensor fusion, Detection and tracking algorithms, Feature extraction, Computer simulations
In this paper we discuss an improved algorithm for sensor- specific data processing and unsupervised data clustering for landmine discrimination. Pre-processor and data- clustering modules forma central part of modular sensor fusion architecture for landmine detection and discrimination. The dynamic unsupervised clustering algorithm is based on Dignet clustering. The self-organizing capability of Dignet is based on the idea of competitive generation and elimination of attraction wells. The center, width and depth characterize each attraction well. The Dignet architecture assumes prior knowledge of the data characteristics in the form of predefine well width. In this paper some modifications to Dignet architecture are presented in order to make Dignet truly self-organizing and data independent clustering algorithm. Information theoretic per-processing is used to capture underlying statistical properties of the sensor data which in turn is used to define important parameter for Dignet clustering such as similarity metrics, initial cluster width etc. The width of the cluster is also adapted online so that a fixed width is not enforced. A suitable procedure for online merge and clean operations is defined to re-organize the cluster development. A concept of dual width is employed to satisfy the competing requirements of compact clusters and high coverage of the data space. The performance of the improved clustering algorithm is compared with base-line Dignet algorithm using simulated data.
IR imaging has been used for landmine detection and discrimination by exploiting the variations in temperature profile on the surface, which may be induced by natural phenomenon such as diurnal cycles or using artificial means such as heated waterjets. While the former method has, in general, not been able to reliably detect and discriminate for small antipersonnel mines, the latter suffers from poor response time. Our previous research has shown that, for waterjet induced thermal images, it takes approximately 15 minutes for the profile of the buried object before it is available on the surface. In this paper we explore the possibility of using thermal profile induced by a single heated water jet when viewed directly into the hole created by the waterjet. A heated waterjet, as it penetrates the ground cover, also digs a hole through which the heat radiates out. The spatial and temporal variation of the heat profile in and around the hole has shown to be rich in information about the buried object. Moreover, the response is much faster when compared to the conduction of heat through the soil to the surface. This paper will present the basic phenomenology and characterize such thermal images induced by single heated waterjet. The spatial and temporal variations are used to detect the presence of an object and its material type. Some possibility to measure the depth of the buried object is also explored.
A neural network-based control system is developed for self- adapting vibration control of laminated plates with piezoelectric sensors and actuators. The conventional vibration control approaches are limited by the requirement of an explicit and often accurate identification of the system dynamics and subsequent 'offline' design of an optimal controller. The present study utilizes the powerful learning capabilities of neural networks to capture the structural dynamics and to evolve optimal control dynamics. A hybrid control system developed in this paper is comprised of a feed- forward neural network identifier and a dynamic diagonal recurrent neural network (DRNN) controller. Sensing and actuation are achieved using piezoelectric sensors and actuators. The performance of hybrid control system is tested by numerical simulation of composite plate with embedded piezoelectric actuators and sensors. Finite element equations of motion are developed based on shear deformation theory and implemented for a plate element. The dynamic effects of the mass and stiffness of the piezoelectric patches are considered in the model. Numerical results are presented for a flat plate. A robustness study including the effects of structural parameter variation and partial loss of sensor and actuator is performed. The hybrid control system is shown to perform effectively in all these cases.
The shape and thermal properties of buried objects can result in a variation in the temperature profile on the surface of the ground. IR imaging has been used to exploit this variation to detect the presence of buried objects. The thermal signature in such cases is normally induced by natural means such as diurnal cycles. This method requires observation at specific times of day and has not in general allowed reliable detection and discrimination, especially for small antipersonnel mines. We have developed a process that uses an array of heated waterjets to rapidly induce a thermal signature of buried objects in the region of interest. The high-pressure, small diameter waterjets penetrate the soil but are deflected by a formed buried objects. A temperature profile on the ground surface is formed due to the radiation and conduction of heat from the water blocked and reflected by the surface of the buried object and the heating of the object itself due to heat transferred from the object to a blurred 2D IR image of the surface. Deblurring and other physics-based image processing techniques are used to correct for the heat diffusion and an estimate can be made of the 3D shape of the part of the buried object which is covered by the waterjet. A time history of the thermal profile is also available when several IR images are acquired after the waterjets are applied. This allows further analysis of the nature of the properties of the buried objects. Known properties of land mines can be used to discriminate them from other buried objects. Shape feature properties based on Fourier descriptors have been developed to allow discrimination of objects.
The aim of this paper is to develop a framework for multi- sensor data fusion for the detection and identification of anti-personnel mines as a part of humanitarian demining project. A two-stage hybrid architecture is proposed to integrate non-homogeneous and dis-similar sensor data from various sensor be in developed as a part of the project. The first stage is used to extract significant information from individual sensor data. Self-organizing neural networks are used to define natural and significant clusters embedded in the sensor data. In this regard two popular self-organizing NN architectures of ART2 and DigNet are studied. The second fusion stage is used to integrate this local sensor information into a global decision. The global decision could be binary as in mine/no-mine decision set, or it could be more complex where identification of the underground mine may be involved. For the present paper, reliable data from different sensor was not available. Extracting different shape feature like moment invariants and Fourier descriptors simulates dis-similar sensor data for simulated shapes. Some results for the performance of the clustering algorithms and the fusion architecture are presented.
A modal dynamic model is developed for the active vibration control of laminated doubly curved shells with piezoelectric sensors and actuators. The dynamic effects of the mass and stiffness of the piezoelectric patches are considered in the model. Finite element equations of motion are developed based on shear deformation theory and implemented for an isoparametric shell element. The mode superposition method is used to transform the coupled finite element equations into a set of uncoupled equations in the modal coordinates. A robust controller is developed using Linear Quadratic Gaussian with Loop Transform Recovery (LQG/LTR) design methodology to calculate the gain and actuator voltage requirements. A neural network controller is then designed and trained offline to emulate the performance of the LQG/LTR controller. Numerical results are presented for a spherical shell showing the variation in initial conditions and structural parameters. The neural network controller is shown to effectively emulate the LQG/LTR controller with slightly improved performance over that of the LQG/LTR controller for some cases.
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