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Full-Text Articles in Engineering
Terrain Referenced Navigation Using Sift Features In Lidar Range-Based Data, Matthew T. Leines
Terrain Referenced Navigation Using Sift Features In Lidar Range-Based Data, Matthew T. Leines
Theses and Dissertations
The use of GNSS in aiding navigation has become widespread in aircraft. The long term accuracy of INS are enhanced by frequent updates of the highly precise position estimations GNSS provide. Unfortunately, operational environments exist where constant signal or the requisite number of satellites are unavailable, significantly degraded, or intentionally denied. This thesis describes a novel algorithm that uses scanning LiDAR range data, computer vision features, and a reference database to generate aircraft position estimations to update drifting INS estimates. The algorithm uses a single calibrated scanning LiDAR to sample the range and angle to the ground as an aircraft …
Cloud-Induced Uncertainty For Visual Navigation, Alyssa N. Gutierrez
Cloud-Induced Uncertainty For Visual Navigation, Alyssa N. Gutierrez
Theses and Dissertations
This research addresses the numerical distortion of features due to the presence of clouds in an image. The research aims to quantify the probability of a mismatch between two features in a single image, which will describe the likelihood that a visual navigation system incorrectly tracks a feature throughout an image sequence, leading to position miscalculations. First, an algorithm is developed for calculating transparency of clouds in images at the pixel level. The algorithm determines transparency based on the distance between each pixel color and the average pixel color of the clouds. The algorithm is used to create a dataset …
Optimal Collision Avoidance Trajectories For Unmanned/Remotely Piloted Aircraft, Nathan E. Smith
Optimal Collision Avoidance Trajectories For Unmanned/Remotely Piloted Aircraft, Nathan E. Smith
Theses and Dissertations
The post-911 environment has punctuated the force-multiplying capabilities that Remotely Piloted Aircraft (RPA) provides combatant commanders at all echelons on the battlefield. Not only have unmanned aircraft systems made near-revolutionary impacts on the battlefield, their utility and proliferation in law enforcement, homeland security, humanitarian operations, and commercial applications have likewise increased at a rapid rate. As such, under the Federal Aviation Administration (FAA) Modernization and Reform Act of 2012, the United States Congress tasked the FAA to provide for the safe integration of civil unmanned aircraft systems into the national airspace system (NAS) as soon as practicable, but not later …
The Differential Vector Phase-Locked Loop For Global Navigation Satellite System Signal Tracking, James J. Brewer
The Differential Vector Phase-Locked Loop For Global Navigation Satellite System Signal Tracking, James J. Brewer
Theses and Dissertations
A novel differential vector phase-locked loop (DVPLL) is derived that takes GNSS code-phase and carrier-phase measurements from a base station and uses them to maintain an integer ambiguity resolved quality solution directly in the vector tracking loop of a rover receiver. The only state variables estimated and used to create the replica code and carrier signals from the base station measurements are three position and two clock states for a static test. Closing the individual loops solely through the navigation filter makes this a pure vector method. For short baselines, where differential atmospheric errors are small, the DVPLL can be …
Non-Linear Optimization Applied To Angle-Of-Arrival Satellite-Based Geolocation, Stephen D. Hartzell
Non-Linear Optimization Applied To Angle-Of-Arrival Satellite-Based Geolocation, Stephen D. Hartzell
Theses and Dissertations
Geolocation is a common application for satellite systems. This involves estimating an object's location (herein called the subject) based on noisy satellite data. Many geolocation methods exist; however, none are tailored specifically for the unique problems faced by satellite systems. Some satellites are so far from the subject being localized that by the time the satellite receives a signal from the subject it might have moved appreciably. Furthermore, some satellites or terrestrial sensors may be much closer to the subject than others. Therefore, sensors may need to be weighted based upon their distance to the subject being localized. In addition, …
Optimal Uav Path Planning For Tracking A Moving Ground Vehicle With A Gimbaled Camera, Riley A. Livermore
Optimal Uav Path Planning For Tracking A Moving Ground Vehicle With A Gimbaled Camera, Riley A. Livermore
Theses and Dissertations
This research develops a path planning algorithm that autonomously controls a UAV to provide convoy overwatch. The optimization algorithm determines the best path to y through developing a cost function that minimizes the control effort of the UAV and the deviation from a desired slant range. A heuristic-based algorithm was developed and implemented on the autopilot to approximate the optimal solution. In flight test, the UAV successfully tracked a moving ground vehicle by continually placing the UAV's loiter point directly above the ground vehicle's current location. This method was called the \follow-me mode and provided the baseline for real-world UAV …
Gps Multipath Reduction With Correlator Beamforming, Jason M. Barhorst
Gps Multipath Reduction With Correlator Beamforming, Jason M. Barhorst
Theses and Dissertations
This research effort investigates the feasibility of beamforming using a single Global Positioning System (GPS) front end. Traditional methods of beamforming use multiple front ends, typically one per antenna element. By enabling a receiver to sample a switched antenna array, the hardware cost of implementing a GPS antenna array can be significantly reduced. Similar techniques of reducing the number of receivers have been used by Locata Corporation in the design of their non-GPS positioning systems. However, Locata Corporation's local transmitters provide a signal strength much higher than GPS's signal strength. For this reason, the inclusion of low-noise amplifiers into the …
Image-Aided Navigation Using Cooperative Binocular Stereopsis, Justin T. Soeder
Image-Aided Navigation Using Cooperative Binocular Stereopsis, Justin T. Soeder
Theses and Dissertations
This thesis proposes a novel method for cooperatively estimating the positions of two vehicles in a global reference frame based on synchronized image and inertial information. The proposed technique - cooperative binocular stereopsis - leverages the ability of one vehicle to reliably localize itself relative to the other vehicle using image data which enables motion estimation from tracking the three dimensional positions of common features. Unlike popular simultaneous localization and mapping (SLAM) techniques, the method proposed in this work does not require that the positions of features be carried forward in memory. Instead, the optimal vehicle motion over a single …