Establishment and Maintenance of Taiwan Geodetic Datum 1997

Abstract

A well-defined three-dimensional geodetic datum is essential to the development of a modernized nation. 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. 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. 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. Taiwan lies at the junction of the Eurasian and Philippine Sea plates. In fact, the September 21, 1999 Chi-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. 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. The 3D coseismic displacement field was recovered from timely maintenance of the new geodetic datum.