Datum-free and weighted constraint adjustments of gravity and GPS base vector nets
| Autor: | Li-Hua Lee, 李莉華 |
|---|---|
| Rok vydání: | 2001 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 89 Weighted constraint and datum-free constraint model are used to adjust relative gravity measurements and GPS baseline vectors. The weighted constraint model is chosen when there exist reliable a priori gravity values or coordinates as additional data, or when it is requested that a lower-order network be attached to an existing network of a higher order. The datum-free model uniquely determines relative gravity values or coordinates among all stations without the need of a fixed station, thus it is suitable for adjusting observations only and for detecting relative changes of gravity or coordinate. A set of relative gravity data in Taiwan was used to test the adjustment models and the developed computer programs in five different cases. The results show that there is no outlier in the data, the estimated reading accuracy of the LaCoste and Romberg G meter (serial number 838) is about 0.02 mgal and the gravimeter drift rate is about 0.9 mgal/month. The coefficients of the long wavelength and periodic components of calibration function are statistically equal to zero. The result from the datum-free solution shows that only one station (Shui-Shang) experiences a significant gravity change due to an aftershock of the 1999 Chi-Chi earthquake. The two adjustment models are then applied to a GPS baseline vector network in the central Taiwan. A method and a computer program is also developed to compute station velocities using multi-campaign baseline vectors. The coordinates and velocities computed by the methods developed in this study are consistent with the results from the BERNES GPS package. The adjustment results show large horizontal motions occurred at the plate east of the Chelungpu Fault after the Chi-Chi earthquake. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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