Determination of northeast Asia's highest peak (Mt. Jade) by direct levelling

This paper demonstrates the results and problems in determining the height of Mt. Jade by direct levelling. Mt Jade is the highest peak in northeast Asia. GPS levelling and trigonometricl levelling were also made to validate the result of direct levelling. For GPS levelling a new geoid model is constructed using Taiwan's latest gravity database and elevation model. The accuracy of the geoid model ranges from cm in coastal plains to dm in high mountains. Helmert deflections of the vertical derived from this geoid model improve the accuracy of trigonometric levelling. Gravity data at benchmarks were collected to compute orthometric corrections for the heights from direct levelling. The Poincaré-Prey reduction and the modified Mader reduction of mean gravity yield orthometric corrections that differ by up to dm near Mt. Jade. The Helmert orthometric height of Mt. Jade determined in this work is 3951.798 m, with a 72-mm commission error. The problem of using a rigorous orthometric height is discussed.