A Study of Ionosphere Single-Layer Model Appropriate Height by Using Continuously Operating Reference Station (CORS)-A Case Study of Taichung City
| Autor: | Chien Wang, 王健 |
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| Rok vydání: | 2017 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 105 Currently, ionospheric delays are the major cause of GPS positioning errors. To solve these errors, dual-frequency measurements may be used. However, dual-frequency instruments are expensive to fabricate. By contrast, a single-frequency receiver combined with an appropriate ionospheric model may achieve the same result; a suitable model can elevate positioning accuracy while lowering overall costs and the amount of materials required. Electron density inside the ionosphere changes over time and varies between different regions, altitudes, and solar power levels. In this study, observation data obtained using GPS at a continuously operating reference station in Taichung were used to build regional ionospheric models. In addition, a single-layer model was utilized to test the hypothetical thin spherical shell heights at different time periods to assess the ionospheric delay errors created and the effects of these errors on positioning accuracy. The objectives were to identify the optimal thin spherical shell height for each time period and to inform GPS single-frequency receiver users regarding what parameters to choose when engaging in ionosphere revisions, effectively enhancing positioning accuracy. First part of the study, three thin spherical shell heights (350, 400, and 450 km) were selected to construct the regional ionospheric models, which were subsequently compared with the IGS global ionospheric model. The experiment results showed that the regional ionospheric models fabricated using the three thin spherical shell heights displayed trends similar to those of the IGS global ionospheric model. Accordingly, this study hypothesized that an increase of thin spherical shell height by 50 km in the thin ionospheric model increases electron content by an average of approximately 3.2 TECU. Second part of the study, A single-frequency, single-point positioning test was performed for 16 time periods, use of regional ionospheric model with a thin spherical shell height of 400 km yielded the greatest positioning accuracy improvement, and that such an improvement was approximately 30% superior to that generated by the IGS global ionospheric model. Finally hypothesized that an increase of spherical shell height by 10 km to single-point positioning test the experiment results showed that the regional ionospheric models appropriate height of Taichung City was 390~420km. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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