Application Of GPS Elevation Fitting In The Ground Subsidence Monitoring

Land subsidence mainly refers to the natural and human factors of disturbance under the action of the environmental geological disasters resulting in the elevation of regional ground declining, as often occurs in the densely populated and industrially developed areas, because its settling velocity is so slow that it is difficult to obviously aware of the hazard area, and its severely damaged, almost unrecoverable characteristis, so it became a more and more popular issue for the sectors of research. Along with continuing improving of various measuring instruments, ground subsidence monitoring methods, monitoring technology, The monitoring of The urban land subsidence has made tremendous progress. Existing monitoring measures are:leveling, trigonometric leveling, digital photogrammetry, GPS measurements, InSAR measurement techniques, as well as GPS and InSAR fusion technology.Traditional leveling, its operating efficiency is low; Trigonometric leveling, in the face of long-distance or even ultra-long-distance monitoring, it still can not meet their requirements in terms of efficiency; Digital measurement techniques, the cost is too high, the device is relatively expensive; Plane accuracy of GPS measurements, its elevation benchmark is the reference ellipsoid spherical, can not be used directly in the project, thus limiting its application to subsidence monitoring; InSAR measurements technology, the technology in precision are highly susceptible to atmospheric error, surface condition, and satellite orbit parameters, thereby affecting its accuracy and reliability; GPS and InSAR fusion technology, its limitations in terms of technology and cost, the technology is not widely promoted. In this paper, combined with GPS measurement techniques and the traditional standard of measurement methods to study, and combined with the characteristics of the land subsidence monitoring, and using GPS leveling technology, using the GPS elevation fit to get the value of the point demanded.These GPS height conversion models can be divided into two categories, one is single model, only use one model to achieve elevation conversion, such as conventional geometric fitting model; another is hybrid models that integrated multiple models, including the model of the same nature mixed and the different nature mixed, such as Kriging. In addition, referencing to the existing model, this paper proposes a new method for choicing the site fitting way that based on the height anomaly terrain, through the data validation, we find both four parts and eight parts are better than conventional methods. In summary, we study on the principle of a variety of fitting models and the characteristics of different fitting models in this article, and proposed a step-by-step hybrid models. This method has the advantages of each model, and better practicality. In this paper, we use the data of the north China region to demonstrate the advantages of this method.