Horizontal datums measure positions (latitude and longitude) on the surface of the Earth, while vertical datums are used to measure land elevations and water depths. There are two main datums in the United States. Geodesists and surveyors use datums to create starting or reference points for floodplain maps, property boundaries, construction surveys, levee design, or other work requiring accurate coordinates that are consistent with one another. For instance, when you want to tell someone how to get to your house, you give them a starting point that they know, like a crossroads or a building address.
In this way, datums act similar to starting points when you give someone directions. When it is completed, users will be able to get accurate heights to within about an inch for most locations around the nation.Ī geodetic datum is an abstract coordinate system with a reference surface (such as sea level) that serves to provide known locations to begin surveys and create maps. This project is called the Gravity for the Redefinition of the American Vertical Datum, or GRAV-D for short. Scientists at the National Geodetic Survey are working on a long-term project to make accurate height measurement better, faster, and cheaper.This update will deliver more accurate water level measurements throughout the Great Lakes. and Canadian partners are undertaking a multi-year initiative to update the International Great Lakes Datum. This update will help improve navigation safety, storm surge prediction, sea-level monitoring, and ecosystem research. Scientists with the Center for Operational Oceanographic Products and Services are updating the National Tidal Datum Epoch - the framework used to measure water levels along U.S.The 3D coseismic displacement field was recovered from timely maintenance of the new geodetic datum.
This massive earthquake not only created significant coseismic displacements among the largest fault movements ever observed from modern earthquakes but also revealed intriguing geophysical and geological phenomena. In fact, the SeptemChi-Chi earthquake of magnitude 7.6 was the largest earthquake of the century to strike the island and severely deformed the crust of central Taiwan. Taiwan lies at the junction of the Eurasian and Philippine Sea plates. The most important aspect of all was that this region is one of the world's most unstable areas with significant annual tectonic movements and frequent major earthquakes.
The objective of this research was to investigate key geodetic issues associated with the establishment and maintenance of a new geodetic datum in the Taiwan region, including Taiwan Island and several offshore islands adjacent to Mainland China. Also, it is of importance for the geodetic datum to be sufficiently accurate at all times to meet the requirements of many scientific and engineering applications, such as crustal deformation monitoring, national charting and mapping, cadastral survey, and precise navigation. A well-defined three-dimensional geodetic datum is essential to the development of a modernized nation.
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