Peter Mumford

Extreme coastal erosion enhanced by anomalous extratropical storm wave direction

Extratropical cyclones (ETCs) are the primary driver of large-scale episodic beach erosion along coastlines in temperate regions. However, key drivers of the magnitude and regional variability in rapid morphological changes caused by ETCs at the coast remain poorly understood. Here we analyze an unprecedented dataset of high-resolution regional-scale morphological response to an ETC that impacted southeast Australia, and evaluate the new observations within the context of an existing long-term coastal monitoring program. This ETC was characterized by moderate intensity (for this regional setting) deepwater wave heights, but an anomalous wave direction approximately 45 degrees more counter-clockwise than average. The magnitude of measured beach volume change was the largest in four decades at the long-term monitoring site and, at the regional scale, commensurate with that observed due to extreme North Atlantic hurricanes. Spatial variability in morphological response across the study region was predominantly controlled by alongshore gradients in storm wave energy flux and local coastline alignment relative to storm wave direction. We attribute the severity of coastal erosion observed due to this ETC primarily to its anomalous wave direction, and call for greater research on the impacts of changing storm wave directionality in addition to projected future changes in wave heights.

Resolution and Accuracy of an Airborne Scanning Laser System for Beach Surveys

AbstractAirborne scanning laser technology provides an effective method to systematically survey surface topography and changes in that topography with time. In this paper, the authors describe the capability of a rapid-response lidar system in which airborne observations are utilized to describe results from a set of surveys of Narrabeen–Collaroy Beach, Sydney, New South Wales, Australia, over a short period of time during which significant erosion and deposition of the subaerial beach occurred. The airborne lidar data were obtained using a Riegl Q240i lidar coupled with a NovAtel SPAN-CPT integrated Global Navigation Satellite System (GNSS) and inertial unit and flown at various altitudes. A set of the airborne lidar data is compared with ground-truth data acquired from the beach using a GNSS/real-time kinematic (RTK) system mounted on an all-terrain vehicle. The comparison shows consistency between systems, with the airborne lidar data being less than 0.02 m different from the ground-truth data when fo...

Open GNSS Receiver Platform

This paper presents results from the open GNSS receiver platform that has been under development at the School of Surveying and SIS at the University of New South Wales since mid 2004. The aim of the project is to create the first open source GNSS receiver design based on Field Programmable Gate Array (FPGA) technology for research and development. The project is on target with many parts complete and initial results looking good. It is hoped that eventually the hardware components along with the FPGA design files and GPS firmware will become available as a development kit and possibly as an integrated IP block available from one of the FPGA providers. The platform consists of a custom circuit board, a baseband processor design and application firmware. Version one of the circuit board has been built and tested. It has a GPS L1 RF front end, Altera FPGA chip and support components. The baseband design is complete and shown to operate correctly. The application firmware has been ported to the new platform and testing and tuning are on-going. Design aspects and results from each component is discussed, followed by ideas for the future.

Performance of a low-cost field re-configurable real-time GPS/INS integrated system in urban navigation

This paper describes a low-cost real-time GPS/INS integrated system based on a field programmable gate array (FPGA) platform and its performance in an urban environment. The system is built on the Alterapsilas Nios II soft-core processor. The embedded software is implemented on the embedded configurable operating system (eCos). The FPGA approach can shorten the research and development period. Its reprogrammable hardware configuration represents a system design methodology of lower risk. It also allows maximum flexibility, being able to integrate a wide range of GPS and INS sensor packages. Many tests have been conducted in various environments, including suburban, a car parking building, highways, country roads, forested mountain area, in tunnels, under bridges, and in urban canyons. The results have demonstrated the functionality of the system including, the stability and accuracy of the time synchronisation mechanism, the performance of the hardware and software architecture, as well as the accuracy of the algorithm. This paper presents the results of the test in Sydney city in real traffic conditions. Severe GPS outages frequently occurred during the test. The results show that the system can bridge all the GPS outages reasonably well even in the heart of the city where GPS signals were completed blocked by the high buildings.