Low cost underwater acoustic localization

Over the course of the last decade, the cost of marine robotic platforms has significantly decreased. In part this has lowered the barriers to entry of exploring and monitoring larger areas of the earth's oceans. However, these advances have been mostly focused on autonomous surface vehicles (ASVs) or shallow water autonomous underwater vehicles (AUVs). One of the main drivers for high cost in the deep water domain is the challenge of localizing such vehicles using acoustics. A low cost one-way travel time underwater ranging system is proposed to assist in localizing deep water submersibles. The system consists of location aware anchor buoys at the surface and underwater nodes. This paper presents a comparison of methods together with details on the physical implementation to allow its integration into a deep sea micro AUV currently in development. Additional simulation results show error reductions by a factor of three.Comment: 73rd Meeting of the Acoustical Society of Americ

Low-Cost Vision Based Autonomous Underwater Vehicle for Abyssal Ocean Ecosystem Research

The oceans have a major impact on the planet: they store 28% of the CO 2 pro- duced by humans, they act as the world’s thermal damper for temperature changes, and more than 17, 000 species call the deep oceans their home. Scientific drivers, like climate change, and commercial applications, like deep sea fisheries and underwater mining, are pushing the need to know more about oceans at depths beyond 1000 meters. However, the high cost associated with autonomous underwater vehicles (AUVs) capable of operating beyond the depth of 1000 meters has limited the study of the deep ocean. Traditional AUVs used for deep-sea navigation are large and typically weigh up- wards of 1000-kgs, thus requiring careful planning before deployment and multi- person teams to operate. This thesis proposes the use of a new vehicle design based around a low-cost oceanographic glass sphere as the main pressure enclosure to reduce its size and cost while maintaining the ability for deep-sea operation. This novel housing concept, together with a minimal sensor suite, enables environmental research at depths previously inaccessible at this price point. The key characteristic that enables the cost reduction of this platform is the removal of the Doppler velocity log (DVL) sensor, which is replaced by optical cameras. Cameras allow the vehicle to estimate its motion in the water, but also enable scientific applications such as identification of habitat types or population density estimation of benthic species. After each survey, images can be further processed to produce full, dense 3D models of the survey area. While underwater optical cameras are frequently placed inside pressure housings behind flat or domed viewports and used for visual navigation or 3D reconstructions, the underlying assumptions for those algorithms do not hold in the underwater domain. Refraction at the housing viewport, together with wavelength-dependent attenuation of light in water, render the ubiquitous pinhole camera model invalid. This thesis presents a quantitative evaluation of the errors introduced by underwater effects for 3D reconstruction applications, comparing low- and high-cost camera systems to quantify the trade-off between equipment cost and performance. Although the distortion effects created by underwater refraction of light have been extensively studied for more traditional viewports, the novel design proposed necessitates new research into modeling the lensing effect of this off-axis domed viewport. A novel calibration method is presented that explicitly models the effect of the glass interface on image formation based on the characterization of optical distortions. The method is capable of accurately finding the position of the camera within the dome and further enables the use of deconvolution to improve the quality of the taken image. Finally, this thesis presents the validation of the designed vehicle for optical surveying tasks and introduces a end-to-end ocean mapping pipeline to streamline AUV deployments, enabling efficient use of time and resources.PHDNaval Architecture & Marine EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/155225/1/eiscar_1.pd

Veneratores lapidum. Long-lasting sacred spaces in the mountain landscape of the Northern Plateau of the Iberian Peninsula.

Dissertação de Mestrado em Arqueologia e Território apresentada à Faculdade de LetrasPresenta-se a tese final do mestrado relativa a Dissertação em Arqueogeografía do Mestrado em Arqueología e Territorio da Universidade de Coimbra. Nas páginas seguintes se defende o uso de uma perspectiva de longa duração nas investigações de rochedos sacralizados, mediante casos práticos de estudo ubicados nas provincias espanholas de Salamanca, Palencia e Ávila. A visão diacrónica permite a identificação de referencias na paisagem que eram frequentadas ao longo de varios procesos históricos, contando com sitios prehitóricos, altomedievais e modernos. A presença de covinhas em muitos de eles representa a única prova da antropização das penhas sacras do entorno visível, utilizadas por estas comunidades como rota de trânsito, santuário, ermidas, ponto de encontro, refúgio ou sendo a origem de mitos populares, criando assim uma ressemantização de espaços sagrados. O estudo se completa com a realização de prospecções nos locais tratados e a elaboração de bacias de visão desde cada um dos sitios. RESUMENSe presenta un trabajo de fin de master relativo a la asignatura de Dissertação em Arqueogeografía perteneciente al Mestrado em Arqueología e Territorio de la Universidad de Coimbra. En las siguientes páginas se defiende el uso de una perspectiva de larga duración para las investigaciones de roquedos sacralizados, a través de casos prácticos de estudio ubicados en las provincias españolas de Salamanca, Palencia y Ávila. La visión diacrónica permite la identificación de referencias en el paisaje que han sido frecuentadas a lo largo de varios procesos históricos, contando con sitios prehistóricos, altomedievales y modernos. La presencia de cazoletas en muchos de ellos representa la única prueba de la antropización de las peñas sacras del entorno visible, utilizadas por estas comunidades como vía de tránsito, santuario, eremitorio rupestre, lugar de reunión, refugio o siendo el origen de mitos populares, creándose una resemantización de los espacios sagrados. El estudio se completa con la realización de prospecciones sobre los lugares tratados y la elaboración de cuencas visuales desde cada uno de los sitios.A master's thesis is presented for the subject of Dissertação em Arqueogeografía of the Mestrado em Arqueología e Territorio from Coimbra’s University. In the following pages, is defended the use of a long-term perspective for investigations of sacred rocky areas, through practical case studies located in the Spanish provinces of Salamanca, Palencia and Ávila. The diachronic vision allows the identification of references in the landscape that have been frequented throughout various historical processes, counting on prehistoric, early middle age and modern sites. The presence of cup-marks in many of them represents the only proof of the anthropization of the sacred rocks of the visible environment, used by these communities as a transit route, sanctuary, rock hermitage, meeting place, refuge or being the origin of popular myths, creating a resemantization of the sacred space. The study is completed with the carrying out of prospections on the treated places and the elaboration of viewsheds from each of the sites. A master's thesis is presented for the subject of Dissertação em Arqueogeografía of the Mestrado em Arqueología e Territorio from Coimbra’s University. In the following pages, is defended the use of a long-term perspective for investigations of sacred rocky areas, through practical case studies located in the Spanish provinces of Salamanca, Palencia and Ávila. The diachronic vision allows the identification of references in the landscape that have been frequented throughout various historical processes, counting on prehistoric, early middle age and modern sites. The presence of cup-marks in many of them represents the only proof of the anthropization of the sacred rocks of the visible environment, used by these communities as a transit route, sanctuary, rock hermitage, meeting place, refuge or being the origin of popular myths, creating a resemantization of the sacred space. The study is completed with the carrying out of prospections on the treated places and the elaboration of viewsheds from each of the sites