Knowledge Resource Center for Ecological Environment in Arid Area
| 报告编号 | NASA-CR-196440, NAS 1.26:196440 |
| 来源ID | NTRS_Document_ID: 19950007214 |
| Measurement and interpretation of crustal deformation rates associated with postglacial rebound | |
| Davis, James L. | |
| 英文摘要 | Analysis of Global Positioning System (GPS) data from two sites separated by horizontal distance of only approximately 2.2 m yielded phase residuals exhibiting a systematic elevation angle dependence. One of the two GPS antennas was mounted on an approximately 1 m high concrete pillar, and the other was mounted on a standard wooden tripod. We performed elevation angle cutoff tests with these data, and established that the vertical coordinate of site position was sensitive to the minimum elevation angle (elevation cutoff) of the data analyzed. For example, the vertical coordinate of site position changed by 9.7 plus or minus 0.8 mm when the minimum elevation angle was increased from 10 to 25. We performed simulations based on a simple (ray tracing) multipath model with a single horizontal reflector, and demonstrated that the elevation angle cutoff test results and the pattern of the residual versus elevation angle could be qualitatively reproduced if the reflector were located 0.1-0.2 m beneath the antenna phase center. We therefore, hypothesized that the source of the elevation-angle-dependent error were multipath reflections and scattering and that the horizontal surface of the pillar, located a distance of approximately 0.2 m beneath the antenna phase center, was the primary reflector. We tested this hypothesis by placing microwave absorbing material between the antenna and the pillar in a number of configurations and analyzed the changes in apparent position of the antenna. The results indicate that (1) the horizontal surface of the pillar is indeed the main reflector, (2) both the concrete and the metal plate embedded in the pillar are significant reflectors, and (3) the reflection can be reduced to a great degree by the use of microwave absorbing materials. These results have significant implications for the accuracy of global GPS geodetic tracking networks which use pillar-antenna configuration identical or similar to the one used here (at the Westford WFRD GPS site). |
| 英文关键词 | ANTENNA DESIGN COMPUTERIZED SIMULATION CRUSTAL FRACTURES EARTH MANTLE ELEVATION ANGLE GLOBAL POSITIONING SYSTEM MICROWAVE TRANSMISSION MULTIPATH TRANSMISSION TECTONICS ABSORBERS (MATERIALS) EMBEDDING ERRORS GEODESY METAL PLATES RAY TRACING REFLECTORS SCATTERING FUNCTIONS TRACKING NETWORKS TRIPODS |
| 出版年 | 1994 |
| 报告类型 | Technical Report |
| 语种 | 英语 |
| 国家 | 美国 |
| URL | http://hdl.handle.net/2060/19950007214 |
| 资源类型 | 科技报告 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/259229 |
| 推荐引用方式 GB/T 7714 | Davis, James L.. Measurement and interpretation of crustal deformation rates associated with postglacial rebound,1994. |
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