A globally consistent and dynamic Canadian gravity reference frame for a modern heighting system and other applications.

摘要

The Canadian gravity database comprises more than about 700000 gravity anomalies observed over a time span of over 50 years and as a result, they have been referenced to different time epochs. For many geodetic applications especially for an accurate geoid determination, the gravity anomaly measurements need to be readjusted and referenced to the same time epoch, and more specifically to the Canadian Gravity Standardization Network (CGSN) adjustment of 2000.; The objective of this work is to find the best estimation procedure to achieve the homogenization of all gravity anomaly measurements as well as estimation of their covariance matrix without resorting to any tedious adjustment process. The estimation procedure is based on the derivation of an experimental covariance function or semivariogram that best describes the differences in gravity values (Dg) between the CGSN-2000 and the old CGSN-71 adjustments in a test area in western Canada. The covariance function or the semivariogram is then used in the Least Squares Collocation (LSC) or Kriging respectively to test its performance in the test area.; The results show that the derived experimental covariance function can be used to homogenize all gravity anomaly measurements across Canada to a high degree of accuracy and estimate their covariance matrix reliably without resorting in the reprocessing and readjustment of all the original gravity data of the National Gravity Data Base (NGDB) that could take many years of intense effort.