GPS Ionospheric Observation Techniques And Its Application In Earthquake

Ionosphere is a part of near-Earth space environment of human life, and is closely related to human activities. Ionospheric observation has a long history, its purpose is to obtain information about the physical parameters of ionosphere. The history of observation in the ionosphere has begun from ground-based detection of the beginning, and gradually developed into a wide range of space observation.The use of observation equipment has experienced from Ionosonde, incoherent scatter radars, to rocket and satellite observation equipment.Using of this remote sense or In-situ observation measurement, people have a certain understanding on the changes of ionosphere space enviroment. However, because of the limitations of these equipments themselves they are difficult to continuously monitor the global ionosphere change. In view of this, it is significan to seek the effective means and techniques of ionospheric observation. While GPS as present an effective means of probing the ionosphere has been widely applied, the total electron content and electron density derived from GPS technique are two important physical parameters which reveal the change of time and space in ionosphere rules and characteristics.This dissertation paper focuses on the GPS ionospheric observation techniques and its application in earthquake. The main works and results can be summarized as follows:(1) The paper has described the ground-based GPS TEC observation techniques and discusses in detail the approach to create the two-dimensional ionospheric model of China region based on the spherical harmonic function. Comparing with the final product provided by the CODE Analysis Center, the calculated results obtained from the paper are equivalent with those derived from the CODE.(2) The paper has completed the LEO precise orbit determination based on Bernese5.0.Comparing with the results provided by GFZ, the three-dimensional orientation of the RMS is less than 10cm.The POD accuracy can meet the requirements of LEO ionospheric inversion. (3) Based on the assumption of spherical symmetry of ionosphere, utilizing raw GPS observation data, applying geometric mapping function, the instrument biases could be calculated by least-square technique. The paper has compared the results with those from COSMIC online publication, and completed the inversion of LEO TEC.(4) Discussing the advantages and disadvantages of three Abel inversion techniques in detailed based on TEC (tradional AIT, SIT and Alternative SIT), and comparing the occultation results retrieved from SIT and Alternative SIT with those obtained from global ionosondes, the paper has drawn some useful conclusions. The paper has discussed the effect of outliers and cycle slips on inversion results, the result show that occultation data preprocessing is very important.(5) In this paper, firstly an improved ionospheric occultation inversion technique is proposed based on the Non-calibrated TEC, and then the technique is applied in the inversion of simulated data and real observation data respectively. The results show that:(1) whether the simulated data or real observation data are used, the inversion results derived from the Non-calibrated TEC are better than those derived from the calibrated TEC technique, especially it is more obvious for low LEO altitudes; (2) based on the above data, some serious errors occur while the electron density profiles are retrieved from the calibrated TEC, on the contrary, the inversion results derived from Non-calibrated TEC are reasonable.(6) The paper has presented the earthquake-ionosphere coupling mechanism, and drawn the result that seismic ionospheric anomaly occur in ionosphere F2 layer through simulation experiments.(7) The paper has discussed the detection method of ionospheric anomaly, detected and analysised Wenchuan earthquake ionospheric anomaly based on GPS observation data, and checked up respectively the earthquake ionospheric anomaly in China since 2004 and in foreign country since 2007. After statistical analysis, the paper has drawn some useful conclusions.