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In light the severe missing and damage to the control points announced in 1980, a total of 8 satellite tracking station, 105 first order satellite points, and 621 second order satellite points were established by GPS surveying technology from 1993 to 1997. This system is named 1997 Taiwan Datum (simply known as TWD97) based on the measurement criteria as shown below:
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The ITRF is adopted with the azimuth BIH(Bureau International de I’Heure) defined as the azimuth at the time of 1984. 0.
The reference ellipsoid announced by IUGG in 1980(GRS80) is adopted as the reference ellipsoid with parameters as shown below:
Semi-major axis (Equatorial radius):a = 6378137 m
Flattening: f =1/298.257222101
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Map projection: 2-degree Transverse Mercator.
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After the 921 Earthquake in 1999, most triangular points in central Taiwan were shifted and could not be used. Therefore, on May 2, 2001 the Ministry of the Interior announced that the surveying datum in the Article 4 of the Cadastral Surveying Implementation Rules should be based on TWD97 system.
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The 2010 results of 1997 Taiwan Datum System (TWD97[2010]): under the effect the tectonic movement, the basic control points in certain areas were significantly shifted such that the surveying results cannot be in compliance with the precision requirements of current mapping operation. Starting from October 2009, the Ministry of the Interior began convening special project meeting and confirmed the adoption of 1997 Taiwan Datum System (TWD97) as the standard framework continually. In the meantime, the 2010 surveying results of 1997 Taiwan Datum System (TWD97 [2010]) was announced on March 30, 2012. The surveying datum and definition of these results are identical to TWD97, yet they are fitted to the 2010.0 time results of international fixed stations.