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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

The Design and Integration of an Airborne Imager and Flight Campaign to Study the Time Evolution and Vertical Structures of Polar Mesospheric Clouds

Reimuller, Jason David 01 May 2007 (has links)
The scientific objective of this study is to design an aircraft flight experiment that will provide airborne imaging data, augmenting satellite data, to advance the fundamental understanding of polar mesospheric clouds (PMCs). By capturing simultaneous top and bottom views of the PMCs, these airborne images will both provide insight into the time evolution of PMCs, and into the micro-features of these clouds, from which gravity waves and other details of the clouds vertical structures may be obtained. These data may help us better understand the driving mechanisms of these clouds and ultimately those elements of global climatic change, which are believed to cause their expanding presence. The proposed imager will use a similar charged-coupled device and interface as that of the Aeronomy of Ice in the Mesosphere’s (AIM’s) Cloud Imager and Particle Size (CIPS) imager and will observe the clouds in both the visible spectra and in a near-ultraviolet spectrum closer to the sensitivity of the CIPS imager. The sensor is to be integrated aboard UTSIs Piper Navajo. Algorithms for satellite intercept trajectories and airborne imager positioning are developed for flight campaigns, scheduled for the 2007 Boreal Summer along a series of airstrips in both Northern Quebec and Alaska.
102

A framework for roadmap-based navigation and sector-based localization of mobile robots

Kim, Jinsuck 15 November 2004 (has links)
Personal robotics applications require autonomous mobile robot navigation methods that are safe, robust, and inexpensive. Two requirements for autonomous use of robots for such applications are an automatic motion planner to select paths and a robust way of ensuring that the robot can follow the selected path given the unavoidable odometer and control errors that must be dealt with for any inexpensive robot. Additional difficulties are faced when there is more than one robot involved. In this dissertation, we describe a new roadmapbased method for mobile robot navigation. It is suitable for partially known indoor environments and requires only inexpensive range sensors. The navigator selects paths from the roadmap and designates localization points on those paths. In particular, the navigator selects feasible paths that are sensitive to the needs of the application (e.g., no sharp turns) and of the localization algorithm (e.g., within sensing range of two features). We present a new sectorbased localizer that is robust in the presence of sensor limitations and unknown obstacles while still maintaining computational efficiency. We extend our approach to teams of robots focusing on quickly sensing ranges from all robots while avoiding sensor crosstalk, and reducing the pose uncertainties of all robots while using a minimal number of sensing rounds. We present experimental results for mobile robots and describe a webbased route planner for the Texas A&M campus that utilizes our navigator.
103

An analysis of navigational instruments in the Age of Exploration: 15th century to mid-17th century

Swanick, Lois Ann 12 April 2006 (has links)
During the Age of Exploration, navigation evolved from a field filled with superstition into a modern science in Portugal, Spain, and England. The most common navigation instruments utilized and their subsequent innovations are discussed. The refinement of these instruments led to increased accuracy in cartography, safer shipping, and increased trade globally in the period. In order to have the most comprehensive collection of navigation instruments, I investigated 165 shipwrecks dated between 1500 and 1700. Each of these vessels have been located, surveyed, and/or excavated in whole or in part. A comprehensive list of these vessels, compiled for the first time, has been included. This thesis analyzes navigation-related artifacts recovered from 27 of these shipwreck sites. These instruments provide the basis to develop a typology for archaeologists to more closely date these finds. The navigation instruments recovered from the wreck of LaBelle (1686) are discussed in detail. These instruments and related historical documents kept by the navigator provide a more comprehensive picture of the instruments’ accuracy and usefulness. This thesis particularly focuses on the nocturnal/planisphere recovered from the site. This unique instrument is one of only four known to exist worldwide and remains accurate enough to be utilized today. Analysis by a modern astronomer has been included, as well as a partial translation of the common names for constellations inscribed on the instrument. These common names provide some important insights into the received knowledge of sailors and non-academic astronomy during this period. It is hoped that this thesis will be of assistance to archaeologists working to identify, study, and appreciate navigational instruments recovered from shipwrecks. With increased documentation and closer dating, these instruments will become a more valuable portion of the archaeological record.
104

Mediated Reality and Location Awareness to Facilitate Topographical Orientation

Torres Solis, Jorge 13 April 2010 (has links)
Topographical orientation is the ability to orient oneself within the environment and to navigate through it to specific destinations. Topographical disorientation (TD) refers to deficits in orientation and navigation in the real environment, and is a common sequela of brain injuries. People with TD often have difficulties interacting with and perceiving the surrounding environment. The literature suggests that patients with TD are likely to benefit from research leading to clinical standards of practice and technology to facilitate topographical orientation. In the light of the above, the objectives of this thesis were to investigate methods of realizing a context-aware, wearable mediated environment system for indoor navigation, and to develop a standard method of quantifying the impact of such a system on indoor navigation task performance. In realizing these objectives, we first conducted an extensive literature review of in-door localization systems. This review served to identify potential technologies for an indoor, in-situ wayfinding assistive device. Subsequently, an automated navigation algorithm was designed. Our algorithm reduced the navigational effort of simulated patients with topographical disorientation while accounting for the physical abilities of the patient, environmental barriers and dynamic building changes. We introduced and demonstrated a novel energy-based wayfinding metric, which is independent of route complexity. An experiment was conducted to identify preferred graphical navigation tools for mediated reality wayfinding guidance. Different combinations of spatial knowledge, graphical presentations and reference frames were considered in the experiment. The data suggested that the locator and minimap are the preferred navigational tools. Two unique optical-inertial localization systems for real-time indoor human tracking were created. The first localization system was oriented to pedestrians, while the second was implemented on a wheelchair. Empirical tests produced localization accuracies comparable to those reported in literature. Finally, a fully operational mediated reality location aware system for indoor navigation was realized. Tests with human participants indicated a significant reduction in physical effort in comparison to the no-tool condition, during wayfinding tasks in an unfamiliar indoor environment. Collectively, the findings and developments of this thesis lay the foundation for future research on wearable, location-based navigational assistance for individuals with wayfinding difficulties.
105

Aircraft takeoff performance monitoring in far-northern regions : an application of the global positioning system

Pinder, Shane Donald 28 April 2003
A design approach for an aircraft takeoff performance monitoring system (TOPMS) is described. In this approach, it is proposed that the Global Positioning System (GPS) in conjunction with a discrete Kalman Filter be used to determine aircraft acceleration, ground speed, and position relative to the end of the runway. A practical evaluation of the feasibility of this proposal showed clear superiority of a GPS-derived acceleration over a more traditional method employing accelerometers. This study found that, when compared to observations from carefully mounted accelerometers, the GPS-derived observation agreed to within 0.10 metres per second squared ninety percent of the time. Advantages of the GPS-derived observation included a modest noise level, insusceptibility to gravity and temperature-influenced variations, and far simplified mounting criteria. A theoretical dynamic model of an aircraft in contact with the ground was developed in consideration of factors pertaining to runways at far-northern Canadian airports. In the model, factors such as runway slope, wind velocity, wheel friction coefficient, and aircraft control settings were considered constant. While variability in any parameter considered constant by the model could influence the performance of a TOPMS, such variability was deemed beyond the scope of this preliminary investigation of a TOPMS designed specifically for the far-northern environment. A device containing a GPS receiver and data acquisition system was designed and certified, then installed in an aircraft operated by an airline servicing far-northern Canadian airports. The data collected in this manner were used to validate the theoretical model. It was concluded that a projection of displacement can be determined to within an uncertainty of fifteen metres in sufficient time to alert the pilot of an unsafe situation.
106

Aircraft takeoff performance monitoring in far-northern regions : an application of the global positioning system

Pinder, Shane Donald 28 April 2003 (has links)
A design approach for an aircraft takeoff performance monitoring system (TOPMS) is described. In this approach, it is proposed that the Global Positioning System (GPS) in conjunction with a discrete Kalman Filter be used to determine aircraft acceleration, ground speed, and position relative to the end of the runway. A practical evaluation of the feasibility of this proposal showed clear superiority of a GPS-derived acceleration over a more traditional method employing accelerometers. This study found that, when compared to observations from carefully mounted accelerometers, the GPS-derived observation agreed to within 0.10 metres per second squared ninety percent of the time. Advantages of the GPS-derived observation included a modest noise level, insusceptibility to gravity and temperature-influenced variations, and far simplified mounting criteria. A theoretical dynamic model of an aircraft in contact with the ground was developed in consideration of factors pertaining to runways at far-northern Canadian airports. In the model, factors such as runway slope, wind velocity, wheel friction coefficient, and aircraft control settings were considered constant. While variability in any parameter considered constant by the model could influence the performance of a TOPMS, such variability was deemed beyond the scope of this preliminary investigation of a TOPMS designed specifically for the far-northern environment. A device containing a GPS receiver and data acquisition system was designed and certified, then installed in an aircraft operated by an airline servicing far-northern Canadian airports. The data collected in this manner were used to validate the theoretical model. It was concluded that a projection of displacement can be determined to within an uncertainty of fifteen metres in sufficient time to alert the pilot of an unsafe situation.
107

Mediated Reality and Location Awareness to Facilitate Topographical Orientation

Torres Solis, Jorge 13 April 2010 (has links)
Topographical orientation is the ability to orient oneself within the environment and to navigate through it to specific destinations. Topographical disorientation (TD) refers to deficits in orientation and navigation in the real environment, and is a common sequela of brain injuries. People with TD often have difficulties interacting with and perceiving the surrounding environment. The literature suggests that patients with TD are likely to benefit from research leading to clinical standards of practice and technology to facilitate topographical orientation. In the light of the above, the objectives of this thesis were to investigate methods of realizing a context-aware, wearable mediated environment system for indoor navigation, and to develop a standard method of quantifying the impact of such a system on indoor navigation task performance. In realizing these objectives, we first conducted an extensive literature review of in-door localization systems. This review served to identify potential technologies for an indoor, in-situ wayfinding assistive device. Subsequently, an automated navigation algorithm was designed. Our algorithm reduced the navigational effort of simulated patients with topographical disorientation while accounting for the physical abilities of the patient, environmental barriers and dynamic building changes. We introduced and demonstrated a novel energy-based wayfinding metric, which is independent of route complexity. An experiment was conducted to identify preferred graphical navigation tools for mediated reality wayfinding guidance. Different combinations of spatial knowledge, graphical presentations and reference frames were considered in the experiment. The data suggested that the locator and minimap are the preferred navigational tools. Two unique optical-inertial localization systems for real-time indoor human tracking were created. The first localization system was oriented to pedestrians, while the second was implemented on a wheelchair. Empirical tests produced localization accuracies comparable to those reported in literature. Finally, a fully operational mediated reality location aware system for indoor navigation was realized. Tests with human participants indicated a significant reduction in physical effort in comparison to the no-tool condition, during wayfinding tasks in an unfamiliar indoor environment. Collectively, the findings and developments of this thesis lay the foundation for future research on wearable, location-based navigational assistance for individuals with wayfinding difficulties.
108

Two novel off-screen navigation techniques

Nezhadasl, Mahtab 23 April 2009 (has links)
In large workspaces that do not fit on the screen space, users have to navigate to various regions outside the viewport to locate items of interest. Researchers have developed a variety of different navigation techniques to improve the performance of working with large workspaces. In this thesis I design, implement, and evaluate two novel navigation techniques to access off-screen content. I call these techniques Multiscale Window and Crystal Ball. The design of these two techniques was based on two hybrid interaction systems WinHop and Multiscale Zoom. Multiscale Window takes advantage of Multiscale Zoom to provide an overview of the context by incorporating full-detail object representations (proxies), and Crystal Ball is an improvement to WinHop. The implemented techniques were designed to alleviate the shortcomings of both hybrid techniques; Multiscale Zoom lacks the ability to provide detail information of overlapped proxies, and WinHop does not facilitate navigation to the off-screen region due to the animation. I evaluated the Multiscale Window and Crystal Ball techniques in two experiments. In the first experiment (N = 14) a Tablet PC with a digital pen as an input device was used. Results showed that there was no significant difference between Multiscale Window and Multiscale Zoom. However, Crystal Ball showed improved effects over WinHop in most tasks. The second experiment (N = 14) compared the same techniques as in experiment one, on a PC with a mouse as input device. The results indicated that subjects were faster with Crystal Ball than WinHop. Like the first experiment, Multiscale Window did not show any significant improvement over Multiscale Zoom. / May 2009
109

Ice navigation with ice compressionin the Gulf of Finland

Berg, Niklas January 2010 (has links)
Safe winter navigation is a hot topic. Not only is the traffic density increasing but theenvironmental considerations are also getting bigger. An oil leakage from a big oiltanker can be of catastrophic proportions in the wrong area and more trafficincreases the risk of an accident. A project that aims for safer winter navigation isSafeWIN. The aim of this project is to develop a forecasting system for compressiveice and thus make winter navigation safer.This thesis is part of above mentioned project and aims to investigate what influenceice compression and ice class has on winter navigation. Vessels are exclusivelyAFRAMAX size tankers sailing on Primorsk in the Gulf of Finland during 2006. Transitdata comes from AIS tracks recorded by the Swedish Maritime Administration. Adatabase with tanker transits has been created and this information is the source forthe studies in this thesis. Included in the database are wind data, ice particulars andtransit information such as speed, and time at different activities during the transit.Average values for a transit has been investigated for comparison and to get a pictureof an average transit.Velocity, waiting time and time with assisting icebreaker are parameters that arebelieved to show how a tanker performs in winter navigation. These parameters arecompared with ice compression and ice class separately to see if there is acorrelation. Ice compression has also been investigated for correlation towards windforce to see if stronger wind generates stronger compression.Using the velocity in different ice compressions an estimate of ice resistance that stemfrom ice compression has been extracted by means of Lindqvist’s formula.
110

A Location Based Service Framework for Pedestrian Navigation

Wieczorek, Natalia January 2011 (has links)
Pedestrian navigation is an emerging technology with high growth market potential. In this report, we present a location based service framework for pedestrian navigation that uses smart phones as client devices and is deployed on an existing Wi-Fi infrastructure in a building. The thesis describes methods and technologies that are used for pedestrian navigation and how they can be combined to achieve an accurate and reliable solution to the navigation problem. A final evaluation indicated that the service can be used in variety of places like university campuses, shopping malls and dense urban areas.

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