Ned H. Witherspoon

Detection of mines and minelike targets using principal component and neural-network methods

This paper introduces a new system for real-time detection and classification of arbitrarily scattered surface-laid mines from multispectral imagery data of a minefield. The system consists of six channels which use various neural-network structures for feature extraction, detection, and classification of targets in six different optical bands ranging from near UV to near IR. A single-layer autoassociative network trained using the recursive least square (RLS) learning rule was employed in each channel to perform feature extraction. Based upon the extracted features, two different neural-network architectures were used and their performance was compared against the standard maximum likelihood (ML) classification scheme. The outputs of the detector/classifier network in all the channels were fused together in a final decision-making system. Two different final decision making schemes using the majority voting and weighted combination based on consensual theory were considered. Simulations were performed on real data for six bands and on several images in order to account for the variations in size, shape, and contrast of the targets and also the signal-to-clutter ratio. The overall results showed the promise of the proposed system for detection and classification of mines and minelike tagets.

Role of sea salt aerosols in the formation of aromatic secondary organic aerosol: yields and hygroscopic properties

Environmental context In the coastal and ocean environment, oil spills and ship movement can produce hazardous, organic aerosols. In this study, the role of sea salt in the formation processes of crude-oil-derived organic aerosols derived was explored, and it was found that sea salt can greatly increase the formation and growth of these toxic aerosols. Understanding of this process is crucial for evaluating the effect of oil spills and ship movements on air quality and human health. Abstract Dual, large (52m3), outdoor chambers were used to investigate the effect of aerosol aqueous phase chemistry on the secondary organic aerosol (SOA) yields of the photooxidation products of aromatic hydrocarbons in the coastal environment. Toluene and 1,3,5-trimethylbenzene were photochemically oxidised in the presence and absence of inorganic seeds (sea salt aerosol (SSA) or NaCl) at low NOx conditions. Overall, the presence of SSA, which was shown to contain water even at low relative humidities (RHs), led to higher SOA yields than the presence of NaCl seeds and the seedless condition. The results suggest that SOA yields in the coastal environment will be higher than those produced in terrestrial environment. To study the effect of SOA formation on the chemical composition of SSA, inorganic species were measured using a particle-into-liquid-sampler coupled to an ion chromatograph. The hygroscopic properties of the SSA internally mixed with SOA were analysed using a Fourier-transform infrared spectrometer. The fresh SSA shows a weak phase transition whereas no clear phase transition appeared in the aged SSA. The depletion of Cl– due to the accommodation of nitric acid and carboxylic acids on the surface of SSA coincides with changes in aerosol hygroscopic properties.

Coastal battlefield reconnaissance and analysis program for minefield detection

The Coastal Battlefield Reconnaissance and Analysis (COBRA) program is a US Marine Corps Advanced Technology Demonstration (ATD). The objective is to design, develop, and demonstrate an unmanned aerial vehicle (UAV) based passive multispectral video sensor subsystem, to detect and locate obstacles and minefields before and during an amphibious assault, and land combat operations in littoral areas. The COBRA ATD system consisting of an airborne sensor subsystem and a ground station subsystem is described along with the testing program.

Simple model of the optical characteristics of bubbles and sediments in seawater of the surf zone

The development of a simple model of the seawater inherent optical properties (IOPs) associated with bubbles and sediments would represent a great advance in surf zone optics. We present one solution for this problem using a combination of geometrical optics and Fraunhofer diffraction. An analytic model of the IOPs of bubbles and sediments (the extinction and absorption coefficients, and phase function) is developed in terms of the moments of the particle size distribution and the complex refractive index of particles.

Navy/Marine Corps innovative science and technology developments for future enhanced mine detection capabilities

JMDT is a Navy/Marine Corps 6.2 Exploratory Development program that is closely coordinated with the 6.4 COBRA acquisition program. The objective of the program is to develop innovative science and technology to enhance future mine detection capabilities. The objective of the program is to develop innovative science and technology to enhance future mine detection capabilities. Prior to transition to acquisition, the COBRA ATD was extremely successful in demonstrating a passive airborne multispectral video sensor system operating in the tactical Pioneer unmanned aerial vehicle (UAV), combined with an integrated ground station subsystem to detect and locate minefields from surf zone to inland areas. JMDT is investigating advanced technology solutions for future enhancements in mine field detection capability beyond the current COBRA ATD demonstrated capabilities. JMDT has recently been delivered next- generation, innovative hardware which was specified by the Coastal System Station and developed under contract. This hardware includes an agile-tuning multispectral, polarimetric, digital video camera and advanced multi wavelength laser illumination technologies to extend the same sorts of multispectral detections from a UAV into the night and over shallow water and other difficult littoral regions. One of these illumination devices is an ultra- compact, highly-efficient near-IR laser diode array. The other is a multi-wavelength range-gateable laser. Additionally, in conjunction with this new technology, algorithm enhancements are being developed in JMDT for future naval capabilities which will outperform the already impressive record of automatic detection of minefields demonstrated by the COBAR ATD.

Detecting blobs in multispectral electro-optical imagery using wavelet techniques

Wavelet processing followed by a neural network classifier is shown to give higher blob detection rate and lower false alarm rate than simply classifying single pixels by their spectral characteristics. An on-center, off-surround wavelet is shown to be highly effective in removing constant-mean background areas, as well as ramping intensity variations that can occur due to camera nonuniformities or illumination differences. Only a single wavelet dilation is tested in a case study, but it is argued that wavelets at different scales will play a useful role in general. Adaptive wavelet techniques are discussed for registration and sensor fusion.

Multiwavelength output from a Nd:YAG/Cr:LiSAF hybrid laser

A prototype solid-state, multispectral hybrid laser has been designed and tested. The laser provides simultaneous outputs at several wavelengths. The hybrid-laser concept is based on the efficient use of flash-lamp-pump energy distributed between two complementary lasing materials, Nd:YAG and Cr:LiSAF, that share the same pump cavity. The prototype Q-switched hybrid laser provides dual-fundamental-wavelength output at 850 and 1064 nm as well as frequency-doubled output at 532 nm. The laser achieved 3.6% slope efficiency (combined) in free-running operation and 2.4% when Q switched. Higher efficiencies can be obtained with improvements in laser crystal quality and pump cavity configuration.

Video-based multispectral detection of land mines: a technology applicable for use in law enforcement

The design and preliminary evaluation of a low cost video based multispectral camera system developed in the Standoff Mine Detection Ground (SMDG) exploratory development project for the US Marine Corps is described. The system is composed of an intensified and gated video camera fitted with six user selectable filters in a synchronous spinning filter wheel which provides a different spectral filter for each video frame. The camera system is microprocessor controlled for automatic exposure and matched with custom designed spectrally corrected optics. The associated analog and digital image storage and processing equipment and techniques are also discussed. This system has been field tested to detect land mines at long standoff distances.

COBRA ATD minefield detection results for the Joint Countermine ACTD Demonstrations

The Coastal Battlefield Reconnaissance and Analysis)COBRA) system described here was a Marine Corps Advanced Technology Demonstration (ATD) development consisting of an unmanned aerial vehicle (UAV) airborne multispectral video sensor system and ground station which processes the multispectral video data to automatically detect minefields along the flight path. After successful completion of the ATD, the residual COBRA ATD system participated in the Joint Countermine (JCM) Advanced Concept Technology Demonstration (ACTD) Demo I held at Camp Lejeune, North Carolina in conjunction with JTFX97 and Demo II held in Stephenville, Newfoundland in conjunction with MARCOT98. These exercises demonstrated the COBRA ATD system in an operational environment, detecting minefields that included several different mine types in widely varying backgrounds. The COBRA system performed superbly during these demonstrations, detecting mines under water, in the surf zone, on the beach, and inland, and has transitioned to an acquisition program. This paper describes the COBRA operation and performance results for these demonstrations, which represent the first demonstrated capability for remote tactical minefield detection from a UAV. The successful COBRA technologies and techniques demonstrated for tactical UAV minefield detection in the Joint Countermine Advanced Concept Technology Demonstrations have formed the technical foundation for future developments in Marine Corps, Navy, and Army tactical remote airborne mine detection systems.

PMMW data collection results

Coastal Systems Station under the sponsorship of the Marine Corps Amphibious Warfare Technology Directorate are exploring the use of a Passive Millimeter Wave (PMMW) sensor for stand off airborne mine detection. In the development of any new technology application, there exist a critical need to develop a balanced modeling and measurement capability. Both will complement one another. Nichols Research has established a physics-based image modeling capability for Passive Millimeter Wave (PMMW) systems. This modeling capability has been used to estimate the performance of a PMMW mine detection system. But, in order to accurately predict the performance of a PMMW imaging system, the background clutter characteristics must be characterized and the modeling results verified against measured data. In fact, in the case of a well designed sensor, the background clutter will define the systems overall performance making accurate knowledge of the clutter statistical variations critical. However currently, there is a lack of high resolution PMMW imagery of backgrounds, due to a lack of data collection instrumentation. This paper will present the results from a preliminary PMMW data collection to provide data for the assessment of a PMMW mine detection system. The data collection results will characterize both surface and buried mine detection capabilities under a variety of conditions. It is a well-established fact that no single sensor will be capable of solving the mine detection problem. Instead, a suite of complementary sensors is required. There is however a lack of an extensive data set of sensor modalities collected in a single sample area. Therefore as a secondary objective of this data collection, several sensor modalities will be used to simultaneously collect mine and minefield data. These results will also be presented.