High Resolution 1:10,000 scale Mapping Strategy of Multi ... - NDMA

to transform Cartesian coordinates to latitude and longitude.
Densification of Geocentric Geodetic Datum
The number of stations directly realized by the geocentric geodetic system is
not enough for practical use. Worldwide there are several hundred realized stations
in ITRF and about twenty stations in WGS84. Therefore it is necessary to increase
the density of the local stations based on the given stations in each nation or area.
Examples of densification projects are NAD83 in North America, SIRGAS in South
America and ETRF in Europe.
International Scenario
Most of the international community is switching over to the geocentric
reference system. The GRS67, GRS80, WGS84 and ITRS are results of the efforts
to arrive at the best possible geocentric system. The developed countries have
already defined their datum on geocentric system. Some of the developing countries
are on the way of realizing their datum. At the XX General Assembly of the
International Union of Geodesists and Geophysicists (IUGG) in 1992, the
International Association of Geodesy (IAG) made the following recommendations in
its Resolution no. 1[IAG,1992]:
“1) that groups making highly accurate geodetic, geodynamic or oceanographic
analysis should either use the ITRF directly or carefully tie their own systems to it”
“4) that for high accuracy in continental areas, a system moving with a rigid [tectonic]
plate may be used to eliminate unnecessary velocities provided it coincides exactly
with the ITRS at a specific epoch,
It is clear that these recommendations allows for the use of other systems
providing they are carefully tied to the ITRS. It is also to be noted that in ITRF the
motions of the individual tectonic plates will cause horizontal coordinates to
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