There are many applications for which small unmanned aerial vehicles (SUAVs) are well suited, including surveillance, reconnaissance, search and rescue, convoy support, and short-range low-altitude perimeter patrol missions. As technologies for microcontrollers and small sensors have improved, so have the capabilities of SUAVs. These improvements in SUAV performance increase the possibility for hazardous missions through mountainous and urban terrain in the successful completion of many of these missions. The focus of this research was on remote terrain navigation and the issues faced when dealing with limited onboard processing and limited payload and power capabilities. Additional challenges associated with canyon and urban navigation missions included reactive path following, sensor noise, and flight test design and execution. The main challenge was for an SUAV to successfully navigate through a mountainous canyon by reactively altering its own preplanned path to avoid canyon walls and other stationary obstacles. A robust path following method for SUAVs that uses a vector field approach to track functionally curved paths is presented along with flight test results. In these results, the average tracking error for an SUAV following a variety of curved paths is 3.4~m for amplitudes ranging between 10 and 100~m and spatial periods between 125 and 500~m. Additionally, a reactive path following method is presented that allows a UAV to continually offset or bias its planned path as distance information from the left and right ranging sensors is computed. This allows the UAV to to center itself between potential hazards even with imperfect waypoint path planning. Flight results of an SUAV reactively navigating through mountainous canyons experimentally verify the feasibility of this approach. In a flight test through Goshen Canyon in central Utah, an SUAV biased its planned path by 3 to 10~m to the right as it flew to center itself through the canyon and avoid the possibility of crashing into a canyon wall.

[Truncated abstract] This thesis describes the development, clinical validation and initial application of a technique for taking measurements of the shape and dimensions of the human upper airway, called anatomical optical coherence tomography (aOCT). The technique uses a transparent catheter containing a rotating optical probe which is introduced transnasally and positioned in the airway and oesophagus. Optical coherence tomography is used to take calibrated cross-sectional images of the airway lumen as the probe rotates. The probe can also be advanced or withdrawn within the catheter during scanning to build up three-dimensional information. The catheter remains stationary so that the subject is not aware of the probe motion. The initial application of the system is research into obstructive sleep apnoea (OSA), a serious condition characterized by repetitive collapse of the upper airway during sleep and an independent risk factor for deaths by heart disease, strokes or car accidents. Measurement of upper airway size and shape is important for the investigation of the pathophysiology of OSA, and for the development and assesment of new treatments. . . We have used aOCT to capture three-dimensional data sets of the airway shape from upper oesophagus to the nasal cavity, undertaken measurements of compliance and other airway characteristics, and recorded dynamic airway shape during confirmed sleep apnoea events in a hospital sleep laboratory. We have shown that aOCT generates quantitative, real-time measurements of upper airway size and shape, allowing study over lengthy periods during both sleep and wakefulness. These features should make it useful for study of upper airway behavior to investigate OSA pathophysiology, and aid clinical management and treatment development.