Researchers at the Severe Storms Research Center (SSRC), Georgia Institute of Technology are attempting to detect tornado formation within severe thunderstorms occurring within the vicinity of Atlanta, Georgia using Doppler radar and non-radar sensors that may provide early tornado warning. The goal of these studies is to increase the warning time of tornado formation within the parent thunderstorm. Currently, GTRI researchers use real time S-band Doppler weather radar data from three National Weather Service (NWS) WSR 88D NEXRAD radars displayed on a work station developed and optimized for tornado detection by the National Severe Storms Laboratory (NSSL). Three NWS radars provide severe weather surveillance coverage of the north Georgia area to determine if a thunderstorm contains the Doppler signature that indicates tornado formation. There is also the capability to display cloud to ground (CG) lightning strikes provided by a national monitoring network. The symbology indicating CG strike location is imposed on the radar reflectivity map. GTRI also uses a local lightning direction finder (DF) system that supplies azimuth and range to the lightning strike. This paper discusses the early lightning channel research and the passive parasitic radar system being operated by the SSRC. Lightning detection tests are also presented.

A high resolution Doppler model of the walking human was developed for analyzing the continuous wave (CW) radar gait signature. Data for twenty subjects were collected simultaneously using an infrared motion capture system along with a two channel 10.525 GHz CW radar. The motion capture system recorded three-dimensional coordinates of infrared markers placed on the body. These body marker coordinates were used as inputs to create the theoretical Doppler output using a model constructed in MATLAB. The outputs of the model are the simulated Doppler signals due to each of the major limbs and the thorax. An estimated radar cross section for each part of the body was assigned using the Lund & Browder chart of estimated body surface area. The resultant Doppler model was then compared with the actual recorded Doppler gait signature in the frequency domain using the spectrogram. Comparison of the two sets of data has revealed several identifiable biomechanical features in the radar gait signature due to leg and body motion. The result of the research shows that a wealth of information can be unlocked from the radar gait signature, which may be useful in security and biometric applications.

The utility of low frequency synthetic aperture radar (SAR) for detecting foliage-concealed targets is examined. A forest simulation has been created using a large set of randomly placed and oriented tree models over a lossy dielectric half-space. Given the size of the targets and the wideband frequencies of interest, it is shown that the problem size quickly grows beyond the capabilities of even supercomputers. As a result, an approximate linear superposition technique is developed to model the response from a large number of targets (T-72 tank plus forest model). Results in the SAR image domain show that the clutter response produced by the collection of trees is higher than the response from the T-72 in all cases except when the tank orientation is broadside to the radar aperture. Examination of the backscattered signature of the T-72 shows that there is a direct correlation between the target response and the physical layout of the vehicle. This connection between shape and response holds promise for future exploitation in ATR algorithm development.

We report on measurements of the index of refraction structure parameter C_n² using an X-band interferometric radar operating over a 3.5 km path in Southern California. These measurements were made by observing signal fluctuations and relating them to the structure parameter. Simultaneous measurements of temperature, atmospheric pressure, and humidity were made at the end points of the range. Values of C_n² ranging from 1.4 x 10^-15 to 6.3 x 10^-15 m^-2/3 were observed over a propagation path that was up to 275 m above ground level. These values are generally much larger than those that would be observed at visible wavelengths under the same conditions because of the contributions of the humidity structure parameter and the cross correlation of the temperature and humidity structure parameters. We also address correlation of these measurements of C_n² with fluctuations in the radar angle-of-arrival.

The University of Florida, Electronic Communications Laboratory (ECL), as part of a project with the Air Force Research Laboratory (AFRL), is investigating the utility of ground penetrating radar (GPR) for airfield evaluations. It is expected that the GPR and the results of current research will assist the Air Force in assessing airfields with less coring and allow more rapid and accurate airfield evaluations by providing continuous estimates of the pavement and subsurface conditions. AFRL has conducted airfield measurements using a high-resolution GPR mounted on a test van. Using time domain data from a pair of ground-coupled antennas, one in bistatic mode and the other in monostatic mode, the thickness of pavement and other subsurface layers can be estimated. In order for GPR to be useful for airfield evaluations, practical considerations such as automated data processing capability and efficient data analysis procedures have also been addressed. This paper will describe novel approaches and signal processing techniques developed for detecting layer interface boundaries and estimating the layer properties using GPR. In addition, the software tools developed to facilitate airfield evaluations will be discussed. Finally, surface layer thickness estimates will be compared to measured cores from a recent airfield assessment.

Law enforcement officers and search-and-rescue workers often face the difficult task of determining the locations of people inside a building or obscured by smoke and debris. To address this problem, Time Domain Corporation (TDC) has developed a real-time, hand-held radar to detect the motion of persons in range and azimuth through non-metallic walls. This radar is a time modulated ultra-wide band (TM-UWB) impulse radar that generates a two-dimensional (2D) representation of moving targets in real time. The intentional transmit power emitted from the radar is comparable to the FCC Part 15, Class B limits. It has the following benefits: (1) covertness because of its ultra-low power noise-like signal, (2) high resolution at low radio frequencies for penetrating building materials, (3) reduced range ambiguities and clutter fold-over because of pseudo-random time modulation, and (4) clutter rejection because of the ultra-wide bandwidth of the signal. In this paper, an outline of the key parameters of the TDC prototype radar RadarVision2000 (RV2000) and a brief description of the algorithm that generates a motion map showing the range and direction of the moving people are presented. Some typical radar images of multiple targets for a variety of building materials and cluttered environment obtained using the prototype are shown. Finally, the paper presents some preliminary results for resolving the targets in the elevation plane along with a processing technique for reducing the intensity of multi-path responses in the images.

Inverse Synthetic Aperture Radar (ISAR) imagery provides an opportunity for 3D reconstruction, because it relies on target motion to provide cross-range resolution and is derived as a temporal sequence. As it moves, the target presents different aspects, which can be integrated to derive the third dimension. Tomasi and Kanade introduced a robust technique for recovering object shape and motion, based on factorization of a matrix that represents the 2D projection equations for a set of points on the target object, as observed in an image sequence. The technique has been applied to orthographic projection Tomasi and Kanade, paraperspective projection Poelman and Kanade, and perspective projection Han and Kanade, but encounters nonlinearities when applied to point perspective projection, which require iterative solution. ISAR projection is naturally well suited for application of the factorization technique because the projection equations are linear. 3D reconstruction may lead to improved performance for automatic target recognition (ATR) procedures and may also be used to enhance human visualization of iamged targets.

The United States Army Space and Missile Defense Command (USASMDC) has interest in a technology demonstration that capitalizes on investment in fire control and smart interceptor technologies that have matured beyond basic research. The concept "SWORD" (Short range missile defense With Optimized Radar Distribution) consists of a novel approach utilizing a missile interceptor and interferometric fire control radar. A hit-to-kill, closed-loop, command guidance scheme is planned that takes advantage of extremely accurate target and interceptor state vectors derived via the fire control radar. The fire control system has the capability to detect, track, and classify multiple threats in a tactical regime as well as simultaneously provide command guidance updates to multiple missile interceptors. The missile interceptor offers a cost reduction potential as well as an enhancement to the kinematics range and lethality over existing SHORAD systems. Additionally, the Radio Frequency (RF) guidance scheme offers increased battlefield weather performance. The Air Defense (AD) community, responding to current threat capabilities and trends, has identified an urgent need to have a capability to counter proliferated, low cost threats with a low cost-per-kill weapon system. The SWORD system will offer a solution that meets this need. The SWORD critical technologies will be identified including a detailed description of each. Validated test results and basic principles of operation will be presented to prove the merit of the past investments. The Deptuy Assistant Secretary of the Army for Research and Technology [DAS(R&T)] has a three-year Science and Technology Program to evaluate the errors and proposed mitigation techniques associated with target spectral dispersion and range gate straddle. Preliminary Bench-Top Experiment results will be presented in this paper.

Electronic Warfare Systems tests, whether performed in the lab or on the range, require extensive configuration of the test equipment, all attributes of which must be stored for later data reduction and analysis. Many tests require similar configurations; it would therefore be useful if general-purpose configuration templates could be built once then reused whenever necessary. In this paper, a data model is developed which stores complex EW-system test configurations. Configurations may be reused at multiple levels. Should new kinds of data be required in the future, the model is extensible. Equally important, the model can be pared down in uncomplicated configuration situations. Finally, less frustration during data reduction and analysis would occur since the model facilitates straightforward data entry. Software that reduces data gleaned from EW-system tests may use this model both to develop databases for configuration storage and as part of the internal model of the reduction software itself.

Step-scanned radar antennas represent a new application of radar technology for detection of targets and estimation of their locations. In this paper we describe a new development called Scan-MUSIC (SMUSIC), which extends the application of the MUSIC algorithm to improve the cross-range resolution of closely spaced point targets with a step-scanned radar. This paper also demonstrates that SMUSIC can be used with radar data obtained with an experimental Millimeter Wave (MMW) coherent scanning radar. While a mathematical proof of resolvability has not yet been established for the scanning antenna, we have shown that we can apply the spatial smoothing method to the SMUSIC algorithm to estimate the closely spaced point targets that are within the beamwidth of the radar antenna. The results show that the targets that are spaced less than 1/4 of the antenna beamwidth and are interfering can be resolved with SMUSIC in constructive interference case. This paper also presents the performance of the SMUSIC superresolution algorithm for the scanning antenna in terms of probability of successful resolution and the total average mean-squared error of target locations, based on the simulated data generated by using an experimental antenna pattern.

Critical to the performance of any synthetic aperture radar (SAR) system is accurate compensation for aircraft motion during the imaging aperture. This is thought to be particularly important for Unmanned Aerial Vehicles (UAVs) operating in poor weather conditions where the aircraft may be subject to pronounced turbulence effects. This paper presents some initial findings of an investigation into the effects of aircraft motion on SAR azimuth point spread function for given levels of motion spectrum suppression as supplied by the radar's motion compensation processing. With validation, this approach will allow indicative levels of SAR performance to be estimated over a wide range of operating conditions and hence provides a useful source of advice when considering procurement options.

A novel method for identifying compartment syndrome is presented. This method is based on a novel device that uses electromagnetic waves in the microwave radio frequency (RF) region and a modified algorithm previously used for the estimation of the angle of arrival of radar signals. In this study, we employ this radio frequency triage tool (RAFT) to the clinical condition of compartment syndrome, which is a clinical condition where blood or edema in the muscle compartment of the leg leads to critical sichemia of that exptremity. In anesthetized pigs, RAFT, can detect changes in the RF signature from a leg is due to 2cc or greater of either blood or slaine (a surrogate of edema). These results are compared to clinical examination. RAFT is superior to clinical examination in its ability to detect compartment syndrome in pgis.

To increase the focusing efficiency, resolving and scanning properties of a flat mm-wave FZP lenses and antennas, and to create different shaped radiation patterns the construction of three-dimensional plate: ogival, spherical, parabolic, conical, etc., for the first time were development and investigated both theoretical and experimentally in mm-waves since 1981. A new possibilities of the diffractional antenna are discussed.

The mm-wave planar Fresnel Zone Plate (FZP) lens and antenna has the advantage of being a flat construction that is cheap, light, and easy to manufacture and have a low losses power in material. To increase the focusing efficiency, resolving and scanning properties of a flat mm-wave FZP lenses and antennas, to use an antenna surfaces as a radome and to create different shaped radiation patterns the construction of three-dimensional plate: ogival, spherical, parabolic, conical, etc., for the first time were development and investigated both theoretical and experimentally in mm-waves since 1981.

The land and rain clutter rejection for radar systems of millimeter band of radiowaves is estimated for some types of the radiated signals (the periodic uncoded pulsed sequence, the pulsed-compression signals, the unmodulated continuous signals and the continuous signals with harmonic frequency modulation). It is shown that the use of periodical uncoded pulsed sequence with unambiguous target range determination is preferable. The use of the complex signals with inpulsed modulation permits to increase the clutter rejection if the signal duration after pulsed compression is less than the uncoded pulse duration. Otherwise the clutter accumulation from the large "lighting" area or volume leads to decreasing of the SCR and increases the clutter power from the sidelobes of the ambiguity function. For the continuous harmonical signal the clutter power from the near zone of radar increases and FM of this signal does not permit to provide the clutter rejection to levels obtained for the pulsed sequence.

Geographic data elements are an essential part of any intelligence information system. Visualization of this data on map displays is indispensable in supporting data analysis for mission objectives. No matter what the application domain, (DoD/State Government/e-commerce) the display of information on a geographic map is no longer a "nice-to-have" feature; it's now a mandatory one. The need for data visualization with map graphics has created an abundant supply of mapping products. The capabilities of these products range from advanced Geographic Information Systems (GIS) to basic products for map graphics presentation. The Core Mapping Application Programming Interface, CMAPI, provides a standardized interface to commercial and government off-the-shelf map engines. Using CMAPI allows application developers and their customers to avoid being locked into a specific vendor. As a result, sites where applications are deployed can avoid having to license multiple products that perform the same function. CMAPI is designed and implemented using software component technology for "plug and play" map engine compatibility. CMAPI front-end software components are easy to integrate with web-based thin-client and multi-platform thick client applications. CMAPI back-end components provide implementation of core mapping functionality using any one of several off-the-shelf map engines. In addition, CMAPI provides an XML import and export capability that allows applications to share map data while using different map engines.

This paper describes an approach for the organization and simplification of high-resolution geometry and imagery data for 3D buildings for interactive city navigation. At the highest level of organization, building data are inserted into a global hierarchy that supports the large-scale storage of cities around the world. This structure also provides fast access to the data suitable for interactive visualization. At this level the structure and simplification algorithms deal with city blocks. An associated latitude and longitude coordinate for each block is used to place it in the hierarchy. Each block is decomposed into building facades. A facade is a texture-mapped polygonal mesh representing one side of a city block. Therefore, a block typically contains four facades, but it may contain more. The facades are partitioned into relatively flat surfaces called faces. A texture-mapped polygonal mesh represents the building facades. By simplifying the faces first instead of the facades, the dominant characteristics of the building geometry are maintained. At the lowest level of detail, each face is simplified into a single texture-mapped polygon. An algorithm is presented for the simplification transition between the high- and low-detail representations of the faces. Other techniques for the simplification of entire blocks and even cities are discussed.

The Naval Research Laboratory's Digital Mapping, Charting and Geodesy Analysis Program is investigating the application of wavelet technology to terrain approximation in 3D mapping. The wavelet transform allows us to obtain the frequency content of gridded elevation data while retraining the spatial context. We use a 2D discrete wavelet transform (DWT) to reduce Digital Terrain Elevation Data to low and high frequency components. The low frequency components represent widespread fluctuations in terrain and over large areas give a very close approximation to the original data set. Each application of a wavelet transform gives us a 75% reduction in the amount of data that must be displayed. A level 2, 2D DWT allows us to represent large amounts of terrain data with only 6.25% of the original data. A reverse transform on the reduced data set makes possible the restoration of any level up to the original data with only minor loss, making the application suitable for multi-resolution systems. This application is also ideal for time-critical applications. Processing 1,073,179 DTED elevations down to 67,304 takes approximately one-half second. Optimized triangulated irregular network algorithms are reported to require over 45 seconds for a similar sized data set. We describe the application of wavelet technology to Internet-based 3D mapping. In addition to custom 2D maps that may consist of vector, raster and gridded data, users may generate 3D maps by area-of-interest.

The increasing use of airwaves for military communication and surveillance and commercial applications places burdens on spectrum use. This crowding of the spectrum presents two broad problem categories. The first is "co-site interference" where numerous transmitters and receivers are physically located in a small area and share a given portion of the spectrum. Under these conditions, a receiver can be "victim" to a co-located transmitter. The second category involves numerous transmitters (typically airborne) well separated from each other but communicating to receivers placed in a relatively small area. The Common Data Link (CDL) refers to a standard protocol for military data delivery and communication. Surveillance platforms such as Tactical Unmanned Aerial Vehicles (TUAV), JSTARS, U2's, Global Hawks will stream high rate surveillance data (radar, visual and/or infrared imagery, etc.) down to ground terminals. As such, bandwidths are wide (100's MHz) and the potential exists for ground receivers to be victim to signals from airborne transmitters other than its desired source. MITRE has developed a CDL Interference Model to assess potential problems in realistic tactical surveillance scenarios. This paper documents the physical basis of the CDL Interference Model as well as the visualization software architecture that integrates the model with ModSAF/OneSAF.

Public infrastructure services like transportation, energy, air quality, water quality, etc., are characterized by a presence of rich information that can be leveraged to provide more efficient support to public infrastructure decision-making. That information has significant geospatial and temporal characteristics and consists of large quantities of data from a variety of data sources that should be stored efficiently and then integrated in a common framework. A mapping between the data elements and their spatial and temporal locations may be used to provide service information (e.g. traffic conditions) in a meaningful form. Service information is, in general, complex, multi-dimensional , physical or abstract information that is intrinsically difficult to represent and manipulate. Visualization techniques, in conjuction with simulation and data modeling can be extremely useful tools to address many public infrastructure issues and problems. In our previous work, a virtual reality based interface for simulation and evaluation of airport Automated People Movers (APMs) has been implemented using Virtual Reality Modeling Language (VRML). That work has been extended to use Extended 3D (X3D) virtual reality standard. Since the X3D standard is based on the Extensible Markup Language (XML), the integration with the available data sources is improved. The paper focuses on issues related to public infrastructures serivces in transportation and how to include and visualize information from the real world in a virtual environment. The real world in transportation includes building structures, streets and other guide-ways, vehicles, pedestrians, control signals, etc. while the transportation data sources provide information about vehicular and pedestrian traffic and current control strategies.

The importance of accurate registration of GPS (Global Positioning System) tracked objects embedded within a GIS (Geographic Information Systems) context has emerged as a critical need in several land, marine, and air navigational systems both for civilian and defense applications. The object of this work is to measure, model and geo-spatially register the positional accuracy of objects carrying GPS receivers against a GIS background. Although positional accuracy is affected by a number of factors, in this work we have focused on GPS modes (standalone or differential), type of environment (urban or foliage), and type of expected movement of objects. The Ashtech Z-12 sensor is used to collect the data. Linear models are used to estimate the errors associated with the horizontal position information. This error is then visualized upon a `1/2 foot resolution aerial imagery of the UCSC (University of California, Santa Cruz) campus. Estimates of speed and direction errors are used to create visualizations of spatio-temporal uncertainty associated with an object walking through the campus.

Over the past several years there has been a broad effort towards realizing the Digital Earth, which involves the digitization of all earth-related data and the organization of these data into common repositories for wide access. Recently the idea has been proposed to go beyond these first steps and produce a Visual Earth, where a main goal is a comprehensive visual query and data exploration system. Such a system could significantly widen access to Digital Earth data and improve its use. It could provide a common framework and a common picture for the disparate types of data available now and contemplated in the future. In particular mcuh future data will stream in continuously from a variety of ubiquitous, online sensors, such as weather sensors, traffic sensors, pollution gauges, and many others. The Visual Earth will be especially suited to the organization and display of these dynamic data. This paper lays the foundation and discusses first efforts towards building the Visual Earth. It shows that the goal of interactive visualization requires consideration of the whole process including data organization, query, preparation for rendering, and display. Indeed, visual query offers a set of guiding principles for the integrated organization, retrieval, and presentation of all types of geospatial data. These include terrain elevation and imagery data, buildings and urban models, maps and geographic information, geologic features, land cover and vegetation, dynamic atmospheric phenomena, and other types of data.

Many ultra-wideband (UWB) synthetic aperture radar (SAR) detection agorithms employ some combination of a set of features, calculated from the incoming raw radar data return, to segregate targets from clutter in a SAR image. Based on the training data, the algorithm designer selects those features that exploit some difference in the physical characteristics between the target class and clutter class. A detection algorithm is then trained to determine values for a set of algorithm parameters that will minimize some sort of error criterion. The physical characteristics that guide the feature selection can change, however, with changes in the attributes of the data collection, such as the depression angle from the radar to the point of interest. When the depression angle changes, the algorithm parameters that were optimal for the training data may no longer be optimal for test data at a different depression angle. We examine the changes in detector performance resulting from depression angle mismatches between the training and test data sets.

An important element of Army transformation efforts is the development of significantly improved munitions. Amongst aggressive goals is a capability to achieve "one shot... at least one kill..." for non-line-of-sight encounters at extended ranges. This objective places unprecedented requirements on sensor technology. A network of sensors must be able to detect, locate, and track the targets; estimate their positions; and periodically uplink that information to the munition, while it is in flight. The Army Research Laboratory formulated the Distributed Sensor Network for Dynamic Retargeting program to address these target-acquisition and dynamic retargeting issues.