Browsing by Author "Cormick, Joshua"
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- ItemLocalization of Bryde's whales using time difference of arrival principles(Stellenbosch : Stellenbosch University, 2021-03) Cormick, Joshua; Versfeld, Jaco; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: The thesis presented gives the detailed practical implementation for a passive audio de-tection system that makes use of time difference of arrival theory to locate the source ofaudio signals emitted from Bryde’s whales. The system consists of three individual float-ing sensors deployed in the water that communicate with the user-unit on the researchvessel. The sensors are comprised of Raspberry Pis and various other specific hardware.The transfer of the sensor readings and the calculations done with said data allows for thelocation of the audio signal to be calculated through a time difference of arrival algorithm.The overall audio signal source localization system is made possible by integrating varioussub-systems. These being; detection, sensor tracking, communication, time synchroniza-tion, and signal location calculation. The theoretical principles behind each of thesesubsystems are discussed as well as their practical implementation, simulations and test-ing. In order to locate the source of an audio signal, one must first be able to identify whetheran input signal to the system is the desired signal. A dynamic time warping algorithm ismade use of in order to detect the desired audio signals. The validity of this algorithm onBryde’s whales has already been proven in the past, however further developments hadto be made when implementing this algorithm in real-time.The locations of the sensors are determined by fitting each sensor with a GPS module.The data that the GPS module feeds to the system is known as NMEA data, this is usedto track the sensors. The sensor positions as well as detection instances are communicatedto the user-unit for processing via LoRa. LoRa is a useful communication technology asthe data can be transmitted directly over long distances.A time difference of arrival algorithm is run on the user-unit. This algorithm makes useof the data received from the sensors to mathematically locate the source of the audiosignal. The location of the sensors and any potential locations for the signal source isshown graphically via a Python interface on the screen attached to the user unit.After testing it was found that the tracking and communication systems function ade-quately. The DTW based detector proved to run sufficiently, though there were instancesof false-positive detections. Additionally, it was found that the TDOA system tested tobe accurate to within several hundred meters when at a scale of kilometers when testedusing a microcontroller in the laboratory.Through testing the various sub-systems of the overall system appears as it would functionsufficiently, though the system was only laboratory tested and was never deployed in theocean due to time constraints.