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Active Microwaves
Published in Iain H. Woodhouse, Introduction to Microwave Remote Sensing, 2006
The geoid is not always the best reference surface, however — what is “mean sea level” to someone living in Switzerland? The geoid is also difficult to use for mapping purposes since it is a real property that must be measured, rather than being a mathematically well-defined reference surface. The latter are referred to as ellipsoids, which are created to provide a common reference surface in order to define vertical location and to form the basis of map projections. In Chapter 10 we will discuss the need for some reference surface onto which we can project our radar image. WGS84 (the World Geodetic System defined in 1984) in one such global ellipsoid that is commonly used in planetary-scale studies and Earth observation. Ellipsoids
Hydrographic surveying
Published in David R. Green, Jeffrey L. Payne, Marine and Coastal Resource Management, 2017
The Earth is an irregular shape, modelled by a sphere on any manageable, physical ‘Globe’ but better represented mathematically by a spheroid, shorter in the polar axis by 21 km than across the equator. The figure of the Earth best known today is often referred to as World Geodetic System 1984 (WGS84) or, more properly, GRS80, i.e. that associated with the US global satellite positioning system, GPS. The long availability of GPS means that much data is gathered with reference to GRS80 or may be transformed from that to a local mapping system.
An initial parameter estimation approach for urban catchment modelling
Published in Urban Water Journal, 2023
Siming Gong, James E Ball, Nicholas Surawski
In the beginning, the catchment remote sensing image and GIS data were projected to the WGS1984/UTM zone 56 (the Universal Transverse Mercator projection system) coordinate system. World Geodetic System, or WGS for short, is a widely used geodetic standard in geodesy, navigation and cartography (Eurocontrol, and IfEN 1998). The purpose of georeferencing and unifying GIS data from different sources is to eliminate the error caused by unit system discrepancy. Then, a GIS layer with pre-defined seven representative surface classes (Tree, Pervious, Impervious, Railway, Roof, Road, Water Body) was integrated with the segmented image of MeanShift to generate the training sample. The training sample contains 5460 small image tiles with the size of 256 × 256 for each tile. Following the data training, the output of the MeanShift algorithm was used as the input of the pixel classifier U-Net to produce a pixel base LULC classification and segmentation map. A schematic diagram of U-Net is demonstrated in Figure 4. Finally, the trained U-Net model was applied to catchment raw remote sensing images to make LULC predictions. As prerequisites, the predicted LULC map was rasterised for computing measurable parameters, and the results were conveyed to determine the inferable parameters. Where measurable parameters mean the features are physically measurable such as LULC areas in this study, and the inferable parameters are determined from the measurable attributions, usually have no physical meaning (Choi and Ball 2002).
Site-specific response of a 5 MW offshore wind turbine for Gujarat Coast of India
Published in Marine Georesources & Geotechnology, 2022
Gujarat is one of the most seismically active regions of India. As per the data of the Global Seismic Hazard Assessment Program (GSHAP), the Gujarat region lies in a moderate to high seismic risk region. All the four seismic zones of India are known to lie in this region (BIS IS 1893 (Part-1) 2016). Thus, evaluation of seismic hazard of Gujarat Coastline for the safe design of offshore wind farm is necessary. For carrying out DSHA analysis, details of potential seismic sources are obtained from the seismotectonic atlas (SEISAT) (Dasgupta et al. 2000), published by the Geological Survey of India (GSI)). Linear seismic sources within a radius of 500 km are considered. The maps have been digitized and georeferenced in ArcGIS (Environmental Systems Resource Institute [ESRI] (2016). The coordinate system is used in World Geodetic System (WGS) 1984. The longitudinal extent of the study area is considered from 67°13′2.905′′E to 74°39′14.598′′E and latitude extent is from 18°6′5.953′′N to 25°28′57.858′′N. Seismic data for a period of 1956–2020 is collected from the USGS website. Data of 200 events have been collected. To prepare a homogenous catalog, all the magnitudes have been converted to moment magnitudes with equations suggested by Das, Wason, and Sharma (2011). Further to remove dependent events, decluttering of data has been done by a method suggested by Reasenberg (1985). Open-source program ZMAP version 7.0 (Swiss Seismological Service Zurich, Switzerland) (Wiemer 2001) is used for decluttering. A total of 44 events are removed and hence 156 events are taken into consideration. The earthquake data is overlapped on a seismotectonic map to identify sources having the potential to generate earthquakes.
A causative analysis on ECDIS-related grounding accidents
Published in Ships and Offshore Structures, 2020
İdris Turna, Orkun Burak Öztürk
In January 2018, the world fleet reached a carrying capacity of 1.9 billion dead-weight tons (62 million dwt) more than in the previous year (UNCTAD 2018). It has been observed that with the increasing numbers of ships in recent years ship sizes, navigation speeds and traffic also increased. Today’s maritime trade has created new requirements for the safe navigation of ships. The ECDIS is a mandatory device that was developed to provide very useful information, such as the ship’s instant position, route and speed, as well as information from other vessels in the region, on the local charts. The subject of this research is to investigate whether this device has a relationship with grounding accidents through case studies. In 1984, the World Geodetic System (WGS-84), a reference system that consists of the model parameters that express the dimensions of the Earth, was created by the United States Department of Defense. In the wake of the WGS-84 coordinate reference system, the NAVSTAR system, the first satellite-based global positioning system, was launched into orbit in 1978. Between 1985 and 1988, the Canadian Hydrographic Center made efforts to create an electronic chart database under the name of the North Sea Project (IHR 1990). In the following years, it was striking that different computer-supported chart systems were developed. The International Hydrographic Organization (IHO) classified the electronic chart systems as Electronic Chart Display and Information System (ECDIS) and Electronic Chart System (ECS) (IHO 2014). The performance standards for the ECDIS devices were first published in November 1995 with the IMO Resolution A.817(19) decisions (IMO 1996). The latest edition of these regulations is IMO Resolution MSC.232(82) decisions published in December 2006 (IMO 2006). Adding regulations containing ECDIS carriage requirements to the International Convention for the Safety of Life at Sea (SOLAS) Chapter V regulation 19 in June 2009, it became mandatory as of 1 July 2012 (IMO 2009). Devices that meet all of these requirements are qualified as ECDIS, and those that do not meet the requirements are qualified as ECS (IHO 2014). There is also a time sheet in SOLAS Section V Rule 19/2.10 related to the equipping of ships with ECDIS devices. According to this sheet, it was made mandatory to equip passenger ships until 2014, tankers until 2015 and lastly cargo ships with ECDIS devices until 2018 (IMO 2009).