WGS84坐標對應於TWD97基準之探討

TWD97為我國現行之測量製圖基準，而GPS衛星定位所使用之坐標系統則為WGS84，這兩種坐標系統在嚴格定義上，會因所依據之坐標框架及參考橢球體之不同，而在坐標值的呈現上出現理論性的差異。然而，本文針對台灣附近區域範圍內，以經緯度每隔30分選取81個網格點進行測試，成果顯示WGS84系統與ITRF94框架之間的點位坐標差異可趨近於2cm；而同一點位之空間坐標分別以WGS84及GRS80橢球體進行化算時，81個網格點之坐標差異量在N、E、h三分量上最大僅達0.02mm。由此一等級之坐標差異特性可知，GPS定位成果在TWD97坐標基準上的運用，將可在測量製圖或導航定位之需求中，具有相當程度的一致性。 The so-called TWD97 has been adopted as a new mapping datum for the Taiwan area. Restrictively, the coordinates based on this datum are different with those defined by the WGS84, which is used as the datum for GPS positioning. The coordinate differences between the two datums are related to the different use of ellipsoid and reference frame on their definitions. This paper is, hence, to investigate the differences between the coordinates referred to TWD97, WGS84 and ITRF94 for the test points around the Taiwan area. The results showed that an approximate 2 cm difference in average was found between those coordinates based on the WGS84 and ITRF94. An insignificant level of less than 0.02 mm difference was also tested from the test points for the three coordinate components. It can be realized from those differences that the coordinates based on the datum of TWD97 or WGS84 are consistent to each other and can be directly applied to any surveying, mapping, and navigation applications in the Taiwan area.

The so-called TWD97 has been adopted as a new mapping datum for the Taiwan area. Restrictively, the coordinates based on this datum are different with those defined by the WGS84, which is used as the datum for GPS positioning. The coordinate differences between the two datums are related to the different use of ellipsoid and reference frame on their definitions. This paper is, hence, to investigate the differences between the coordinates referred to TWD97, WGS84 and ITRF94 for the test points around the Taiwan area. The results showed that an approximate 2 cm difference in average was found between those coordinates based on the WGS84 and ITRF94. An insignificant level of less than 0.02 mm difference was also tested from the test points for the three coordinate components. It can be realized from those differences that the coordinates based on the datum of TWD97 or WGS84 are consistent to each other and can be directly applied to any surveying, mapping, and navigation applications in the Taiwan area.