Wave Radars

A comparison of concepts and techniques
Radar Remote Sensing of ocean surface waves may in general be defined as measuring characteristics of the sea surface by means of electromagnetic waves so that the sea surface is itself not disturbed. The electro-magnetic waves transmitted by the radar antenna are scattered back from the sea surface, modulated in amplitude and phase or frequency by the interaction with the sea surface in motion. This modulation carries information about sea-surface characteristics, surface waves and currents. Oceanographic data is extracted from the backscatter signal by sophisticated signal processing and data analysis. Why remote sensing? Surface ocean waves may be measured by... (read more)
2008-01-01 01:00:00

Sea Levels and the Coast

The oceans are a central part of the global climate system. As Roger Revelle, one of the early directors of the Scripps Institute of Oceanography, said, “The oceans exert a profound influence on mankind and indeed upon all forms of life on Earth. The oceans are inexhaustible sources of water and heat, and control the climate of many parts of the world.” He also recognised that “human beings are now carrying out a large-scale geophysical experiment of a kind that could have not have happened in the past nor be reproduced in the future”. Roger Revelle’s thoughts have even more... (read more)
2007-10-27 12:00:00

Sea Level Rise Modelling

In a Caribbean Small Island Developing State
In 2009, a research project was implemented to study the potential socio-economic impacts of climate change upon coastal communities in Canada and the Caribbean. Grande Riviere in Trinidad and Tobago, one of the study sites, is an important nesting site for leatherback turtles. Turtle watching, part of eco-tourism conducted in that part of the country, is an important source of income for the community. Any significant rise in mean sea level may negatively impact the turtles’ nesting sites and consequently negatively impact Grande Riviere’s socio-economic wellbeing. Hydrographic and topographic surveying techniques and GIS were used to construct spatial models that... (read more)
2011-12-19 04:03:39

“Developing by Leaps and Bounds”

Hydro international Interviews Shou Shunbao, Manager, Da Hua Hydrographic Surveying Company, Shangha
It may look as though Europe, the USA and Canada, followed by Australasia, dominate the hydrographic world scene. But there must also be enormous potential in the area north of the Far East: Vietnam, China, Japan, etc. In particular, the economy in China is growing fast and, with her long coastline and dependence upon shipping, China must see a considerable amount of hydrographic work. Hydro INTERNATIONAL interviewed Mr Shou Shunbao, manager with Da Hua Hydrographic Surveying Company of Shanghai, to obtain more information on hydrographic activities in the area. Shou Shunbao, born in November 1955, graduated from Nanjing College of... (read more)
2008-01-01 01:00:00

Geospatial Data Updating at Sea

The Network Centric Mapping Database (NCMD) Web Service Design
A growing problem exists with forward-deployed electronic chart display and information systems (ECDIS) in obtaining and updating geospatial data(electronic nautical charts). This problem is commonly referred to as distributing geospatial data over the “last tactical mile”. As a solution to this problem, the US Navy has developed software called “Network Centric Mapping Database (NCMD)”. NCMD is a software capability that automates data distribution, with a focus on geospatial data (vector map data, raster map data or imagery). NCMD has been developed as a web service and multi-tiered software application that allows deployed C4ISR system to autonomously obtain and update geospatial... (read more)
2007-07-13 12:00:00

Measuring the Uncertainty of a Swath Bathymetric Sonar

A Statistical Analysis for System Performance and IHO Compliance
In the last few decades, substantial efforts have been made to improve and facilitate the way hydrographic data is obtained. One technology is the EdgeTech 4600, an interferometric phase difference sonar. Unlike traditional interferometers, the EdgeTech 4600 is the first of its kind to offer complete swath coverage of the seafloor, even at nadir. Combining this kind of coverage with a vertical accuracy that exceeds IHO Special Order requirements in depths less than 30 metres, results in a sonar with superior area coverage rates, especially in shallow water. In the summer of 2012, bathymetric survey data was collected using an... (read more)
2013-05-23 02:50:53

Ice Navigation and the ­Electronic Age

Still No Perfect Electronic Solution to the Challenges of Ice Navigation
Ice navigation is more of an art than a science, and like most arts, does not fit neatly into any scheme for enhancement by electronic means. It is an art learned in theory at navigation school, and perfected by many years of practical experience in forcing ships though ice. The successful ice-navigator is living proof that the human brain processes data faster, and with more accurate results for correct decision-making, than any computer currently in service. Thus, it becomes clear that electronic assistance to the process will consist mainly of the provision of tools, which will not only make the... (read more)
2013-01-18 02:19:55

The MRU and SRF Aligned (I)

With increasing accuracies of positioning and multi-beam systems, alignment of the motion reference unit (MRU) is becoming increasingly important. Although most (if not all) multi-beam surveyors use the patch-test to resolve the angular offsets between the multi-beam head and the MRU, this test does not give us the angular offsets between the MRU and the ship’s reference frame (SRF). In addition to this, any misalignment between the vertical rotation axis of the MRU and the SRF (yaw-angle) will introduce cross-talk between pitch and roll.<P> The alignment of the threeaxes is also becoming increasingly important at shallower depths as we should... (read more)
2009-01-05 12:00:00

Exploring Coral Reef Sustainability

The Island of Bonaire in the Southwest Caribbean, a Marine Protected Area since 1979, has one of the most pristine coral reefs in the region. The last synoptic survey of the leeward coast was by the Dutch scientist Dr Fleur van Duyl in the 1980s and parts of the deeper reef have never been mapped. In January 2008, the US National Oceanic and Atmospheric Administration (NOAA) funded a unique expedition to Bonaire, deploying three compact Autonomous Underwater Vehicles (AUVs) carrying various oceanographic instrumentation packages and a swath bathymetry sonar.<p> The crystal-clear watersand schools of reef fish made an enchanting setting... (read more)
2008-08-27 12:00:00

A Life-changing Voyage

On New Year’s Day 1916, S. Davis Winship, a young Coast and Geodetic Survey (C&GS) officer, began a life-changing voyage, one that would take him far from his New England roots to a life in an exotic tropical land. Much of what follows is in Winship’s own words. Prior to embarking for the Philippine Islands, he had been in the C&GS for two years and had worked off the rocky shores of New England, the comparatively calm waters of Chesapeake Bay and the sounds of North Carolina, and in the deep, but pinnacle-studded, waters of Alaska’s Inside Passage. He arrived... (read more)
2017-05-16 03:11:52
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