Engineering Commons^™

Digital Holography Efficiency Experiments For Tactical Applications, Douglas E. Thornton

Theses and Dissertations

Digital holography (DH) uses coherent detection and offers direct access to the complex-optical field to sense and correct image aberrations in low signal-to-noise environments, which is critical for tactical applications. The performance of DH is compared to a similar, well studied deep-turbulence wavefront sensor, the self-referencing interferometer (SRI), with known efficiency losses. Wave optics simulations with deep-turbulence conditions and noise were conducted and the results show that DH outperforms the SRI by 10's of dB due to DH's strong reference. Additionally, efficiency experiments were conducted to investigate DH system losses. The experimental results show that the mixing efficiency (37%) is …

Improving Detection Of Dim Targets: Optimization Of A Moment-Based Detection Algorithm, Shannon R. Young

Theses and Dissertations

Wide area motion imagery (WAMI) sensor technology is advancing rapidly. Increases in frame rates and detector array sizes have led to a dramatic increase in the volume of data that can be acquired. Without a corresponding increase in analytical manpower, much of these data remain underutilized. This creates a need for fast, automated, and robust methods for detecting dim, moving signals of interest. Current approaches fall into two categories: detect-before-track (DBT) and track-before-detect (TBD) methods. The DBT methods use thresholding to reduce the quantity of data to be processed, making real time implementation practical but at the cost of the …

Estimation Of Size And Rotations Of Icebergs From Historical Data Utilizing Scatterometer Data, Jeffrey Scott Budge

Theses and Dissertations

In this thesis, the development and methodology of a new, consolidated BYU/NIC Antarctic Iceberg Tracking Database is presented. The new database combines data from the original BYU daily iceberg tracking database derived from scatterometers, and the National Ice Center's weekly Antarctic iceberg tracking database derived from mostly optical and infrared sensors. Using this data, interpolation methods and statistical analyses of iceberg locations are discussed. The intent of this database is to consolidate iceberg location data in order to increase accessibility to users.Active microwave remote sensing instruments are used to track tabular icebergs and provide a daily estimate of their positions …

Extension Of The Quikscat Sea Ice Extent Data Set With Oscat And Ascat Data, Jordan Curtis Hill

Theses and Dissertations

Polar sea ice measurements are an important contribution to global climate models. Passive and active microwave remote sensing instruments are used to track global trends in polar sea ice growth and retreat from day to day. A scatterometer sea ice extent data set is valuable for comparison with other radiometer data sets and ground based measurements. This scatterometer sea ice record began with the NASA Scatterometer (NSCAT) and continued with the Quick Scatterometer (QuikSCAT) data set. The Ku-band Oceansat-2 scatterometer (OSCAT) is very similar to the Quick Scatterometer, which operated from 1999 to 2009. OSCAT continues the Ku-band scatterometer data …

Analysis, Validation, And Improvement Of High-Resolution Wind Estimates From The Advanced Scatterometer (Ascat), Jeffrey Richard Blodgett

Theses and Dissertations

The standard L2B ocean wind product from the Advanced Scatterometer (ASCAT) is retrieved as a 25 km product on a 12.5 km grid. Ultra-high resolution (UHR) processing allows ASCAT wind retrieval on a high-resolution 1.25 km grid. Ideally, such a high-resolution sample grid provides wind information down to a 2.5 km scale, allowing better analysis of winds with high spatial variability such as those in near-coastal regions and storms. Though the wind field is sampled on a finer grid, the actual data resolution needs to be validated. This thesis provides an analysis and validation of ASCAT UHR wind estimates in …

Sea Ice Mapping Using Enhanced Resolution Advanced Scatterometer Images, Steven Joseph Reeves

Theses and Dissertations

Sea ice is of great interest due to its effect on the global climate, the Earth's ecosystem, and human activities. Microwave remote sensing has proven to be an effective way to measure many of the characteristics of sea ice. In particular, several algorithms map the daily sea ice extent using a variety of instruments. Enhanced resolution images generated from the Scatterometer Image Reconstruction (SIR) algorithm can be used to generate a high resolution ice extent map. Previous algorithms using SIR images were developed for scatterometers which are no longer operational. The Advanced Scatterometer (ASCAT) is a newer scatterometer which has …

Target Classification Of Canonical Scatterers Using Classical Estimation And Dictionary Based Techniques, G. Barry Hammond Ii

Theses and Dissertations

This research effort will utilize a hierarchical dictionary-based approach for canonical shape classification within measured synthetic aperture radar (SAR) phase history data. This primary goal of this research is to develop an efficient framework for dictionary based SAR feature extraction using modi ed 3-D radar scattering models. Previous work in this area relies on maximum likelihood (ML) estimation and similar approaches to extract shapes using 2-D signal models. We include characterizations of shape model redundancies caused by similar shape scattering responses. Simulated SAR collection methods, including frequency, elevation aspect, and polarization diversities, are modeled to show reductions in inter-atom correlation. …

The Effect Of Synthetic Aperture Radar Image Resolution On Target Discrimination, John E. Mcgowan

Theses and Dissertations

This research details the effect of spatial resolution on target discrimination in Synthetic Aperture Radar (SAR) images. Multiple SAR image chips containing targets and non-targets are used to test a baseline Automatic Target Recognition (ATR) system with reduced spatial resolution. Spatial resolution is reduced by lowering the pixel count or synthesizing a degraded image by filtering and reducing the pixel count. A two-parameter Constant False Alarm Rate (CFAR) detector is tested, and three feature sets, size, contrast, and texture, are used to train a linear classifier and to estimate probability density functions for the two classes. The results are scored …

Development And Demonstration Of A Field-Deployable Fast Chromotomographic Imager, Daniel C. O'Dell

Theses and Dissertations

A field deployable hyperspectral imager utilizing chromotomography (CT), with a direct vision prism (DVP) as the dispersive element, has been constructed at AFIT. This research is focused on the development and demonstration of the CT imager. An overview of hyperspectral imaging, chromotomography, a synopsis of reconstruction algorithms, and other CT instruments are given. The importance of component alignment, instrument calibration, and exact prism angular position data are discussed. A simplistic \shift and add" reconstruction algorithm was utilized for this research. Although limited in its ability to reconstruct a spatially and spectrally diverse scene, the algorithm was adequate for the testing …

The Navigation Potential Of Ground Feature Tracking, Guner Mutlu

Theses and Dissertations

This research effort examines the reduction of error in inertial navigation aided by vision. This is part of an effort focused on navigation in a GPS denied environment. The navigation concept examined here consists of two main steps. First, extract the position of a tracked ground object using vision and geo-locate it in 3 dimensional navigation frame. In this first step multiple positions of the UAV are assumed known; think of a synthetic aperture. The only information about the tracked ground objects/features is the unit vector that points to the objects from the center of the camera. Two such vectors …

Abstracting Gis Layers From Hyperspectral Imagery, Torsten E. Howard

Theses and Dissertations

Modern warfare methods in the urban environment necessitates the use of multiple layers of sensors to manage the battle space. Hyperspectral imagers are one possible sensor modality to provide remotely sensed images that can be converted into Geographic Information Systems (GIS) layers. GIS layers abstract knowledge of roads, buildings, and scene content and contain shape files that outline and highlight scene features. Creating shape files is a labor-intensive and time-consuming process. The availability of shape files that reflect the current configuration of an area of interest significantly enhances Intelligence Preparation of the Battlespace (IPB). The solution presented in this thesis …

A Wide Area Bipolar Cascade Resonant Cavity Light Emitting Diode For A Hybrid Range-Intensity, Reginald J. Turner

Theses and Dissertations

This dissertation focused on the development of an illuminator for the HRIS. This illuminator enables faster image rendering and reduces the potential of errors in return signal data, that could be generated from extremely rough terrain. Four major achievements resulted from this work, which advance the field of 3-D image acquisition. The first is that the TJ is an effective current spreading layer for LEDs with mesa width up to 140 micrometers and current densities of approximately 1 x 10⁶ Amp/square centimeter. The TJ allows fabrication of an efficient illuminator, with required geometry for the HRIS to operate as …

Monitoring The Antarctic Ice Sheet From Space, Benjamin Rule Lambert

Theses and Dissertations

The Antarctic ice sheet is a geophysically - and in an age of growing concern about global warming, geopolitically - important portion of Earth. The composition and dynamics of the Antarctic ice sheet influence global climate patterns, global sea level and the planet's radiation budget. Recent evidence also suggests that the long term stability of portions of the ice sheet may be in jeopardy. In this thesis I use data from three Ku-band space-borne scatterometers to monitor changes in the backscatter signature of the Antarctic ice sheet from 1978 through 2007. Significant changes in backscatter, which result from geophysical changes …

Hyperspectral-Augmented Target Tracking, Neil A. Soliman

Theses and Dissertations

With the global war on terrorism, the nature of military warfare has changed significantly. The United States Air Force is at the forefront of research and development in the field of intelligence, surveillance, and reconnaissance that provides American forces on the ground and in the air with the capability to seek, monitor, and destroy mobile terrorist targets in hostile territory. One such capability recognizes and persistently tracks multiple moving vehicles in complex, highly ambiguous urban environments. The thesis investigates the feasibility of augmenting a multiple-target tracking system with hyperspectral imagery. The research effort evaluates hyperspectral data classification using fuzzy c-means …

Particle Filter Based Mosaicking For Forest Fire Tracking, Justin Mathew Bradley

Theses and Dissertations

Using autonomous miniature air vehicles (MAVs) is a cost-effective, simple method for collecting data about the size, shape, and location characteristics of a forest fire. However, noise in measurements used to compute pose (location and attitude) of the on-board camera leads to significant errors in the processing of collected video data. Typical methods using MAVs to track fires attempt to find single geolocation estimates and filter that estimate with subsequent observations. While this is an effective method of resolving the noise to achieve a better geolocation estimate, it reduces a fire to a single point or small set of points. …

Phase Diversity And Polarization Augmented Techniques For Active Imaging, Peter M. Johnson

Theses and Dissertations

A multi-frame active phase diversity imaging (APDI) algorithm is derived for coherent light statistics and demonstrated. In addition to conventional focal-plane and diversity-plane data, a statistical description for pupil-plane (PP) intensity is formed and included in the derivation. The algorithm is implemented and characterized via Monte Carlo simulation. Analysis shows that it's robust, insensitive to detection noise for SNR ? 7, performs well for SNR's as low as 2, and that the effect of system configuration on optimal parameters is minimal. Furthermore, introduction of PP data results in a 60% better reconstruction from dynamically aberrated data than obtained using only …

Reconstruction Of Chromotomographic Imaging System Infrared Hyperspectral Scenes, Malcolm G. Gould

Theses and Dissertations

Hyperspectral imagery providing both spatial and spectral information has diverse applications in remote sensing and scientific imaging scenarios. The development of the Chromotomographic Imaging System (CTIS) allows simultaneous collection of both spatial and spectral data by a two-dimensional (2D) focal plane detector array. Post-processing of the 2D detector data reconstructs the three-dimensional (3D) hyperspectral content of the imaged scene. This thesis develops Estimation Theory based algorithms for reconstructing the hyperspectral scene data. The initial algorithm developed reconstructs the 3D hyperspectral scene data cube. An additional algorithm reconstructs a matrix comprised of one spectral dimension and one compound spatial dimension. This …

Simulating A Chromotomographic Sensor For Hyperspectral Imaging In The Infrared, Anthony J. Dearinger

Theses and Dissertations

Hyperspectral imaging systems passively sense radiant electromagnetic energy from a remote scene to form a three dimension profile of the remote scene. The data contained in this profile describes real images of the remote scene for a certain number of spectral wavelength bands across a finite spectral range of electromagnetic radiation. Typical grating type hyperspectral imaging systems collect spectral electromagnetic radiation in the visible and near infrared spectral range, by incrementally scanning across the spatial extent of the remote scene. The legacy of low optical throughput because of the optical scanning techniques employed in these systems means adapting these systems …

Wind Scatterometry With Improved Ambiguity Selection And Rain Modeling, David W. Draper

Theses and Dissertations

Although generally accurate, the quality of SeaWinds on QuikSCAT scatterometer ocean vector winds is compromised by certain natural phenomena and retrieval algorithm limitations. This dissertation addresses three main contributers to scatterometer estimate error: poor ambiguity selection, estimate uncertainty at low wind speeds, and rain corruption. A quality assurance (QA) analysis performed on SeaWinds data suggests that about 5% of SeaWinds data contain ambiguity selection errors and that scatterometer estimation error is correlated with low wind speeds and rain events.

Ambiguity selection errors are partly due to the "nudging" step (initialization from outside data). A sophisticated new non-nudging ambiguity selection approach …

Modeling Electromagnetic Wave Propagation In Electrically Large Structures, Jon Wallace

Theses and Dissertations

Existing unified numerical electromagnetic methods are often unable to analyze electrically large structures due to the amount of memory and processing power required, necessitating approximate analyses with limited applicability. In this research a hybrid modeling methodology is adopted to solve these complex problems more efficiently than unified numerical methods and more accurately than analytical methods. Electromagnetic modeling problems are divided into two or more levels of scale. Each level analyzes a specific level of detail and only promotes the required information to the next level. The method is demonstrated by successful application to three important problems: (1) remote sensing of …

Polar Sea Ice Mapping For Seawinds, Hyrum Spencer Anderson

Theses and Dissertations

In recent years, the scientific community has expressed interest in the ability to observe global climate indicators such as polar sea ice. Advances in microwave remote sensing technology have allowed a large-scale and detailed study of sea ice characteristics. This thesis provides the analysis and development of sea ice mapping algorithms for the SeaWinds scatterometer. First, an in-depth analysis of the Remund Long (RL) algorithm for SeaWinds is performed. From this study, several improvements are made to the RL algorithm which enhance its performance. In addition, a new method for automated polar sea ice mapping is developed for the SeaWinds …

High Resolution Wind Retrieval For Seawinds On Quikscat, Jeremy Blaine Luke

Theses and Dissertations

An algorithm has been developed that enables improved the resolution wind estimates from SeaWinds data. This thesis presents the development of three key portions of the high resolution wind retrieval algorithm: Compositing individual σ-0 measurements and Kp, Retrieved wind bias correction, and ambiguity selection for high resolution winds. The high resolution winds produced by this algorithm are expected to become a useful resource for scientists and engineers studying the ocean winds. The high resolution wind retrieval algorithm allows wind to be retrieved much closer to land than is available from the low resolution winds estimated from the same scatterometer by …