The statistical relationship of the observed gravity anomalies with height, and their comparison with the model‐predicted anomalies in Taiwan Island

Abstract

This study examines the approximately linear relation between free‐air anomalies and topographic heights in Taiwan Island. The resulting statistics shows that there is not a significant linear relation in plain regions, and a strongly, significant linear relation in mountainous regions between the free‐air anomalies and elevations. There are 15 independently observed gravity values were used to check the correlation and evaluate the accuracy of prediction. It has been found that the differences between observed and predicted free‐air (or bouguer) gravity anomalies in mountainous regions have a mean and standard deviation of ‐2.23±9.95 mgals. The global geopotential free‐air anomalies on GRS80 for Taiwan Island have also been predicted using the OSU91A geopotential coefficient set up to degree and order 360. Comparisons have been made between these free‐air anomalies determined from the OSU91A 1F geopotential coefficient set, and terrestrial point gravity anomalies. It has also been found that the mean difference between the OSU91A model derived anomalies and 243 actual point free‐air anomalies is 16.8 mgal with a root mean square error of 48 mgal. The significantly linear relation, between free‐air anomalies and elevations in mountainous regions, obtained from this study can help to predict the needed gravity anomalies for rigorous orthometric correction used in precise leveling of Taiwan Island.

Key words :

• Free‐air anomalies
• geopotential
• root mean square