The Application Of GNSS Precise Positioning In The Airport Construction Surveying In High-elevation Mountain Areas

As a navigation and positioning method based on space,GNSS technology can provide three-dimensional coordinate for a point on the surface or near-earth space around the clock,with the advantages of wide range,high precision,low cost,real-time and high efficiency,no accumulated,etc.It has been widely used in the position and orientation survey in the construction projects.The use of GNSS technology improves the efficiency and precision of the airport construction surveying engineering greatly,and had solved the problems that the traditional measuring methods can't.Due to the present situation that more and more new airports are built at high-elevation mountain areas or remote regions,there are still some difficult problems to be solved.Aimed at the all problems in the airport construction surveying engineering at high-elevation mountain areas or remote regions mentioned above,such as control survey,the relative relationship between two airports,coordinate transformation,and so on.This paper proposes relevant solutions based on the theory and application of GNSS,positioning technology and demonstrates with practical engineering projects and simulation experiments.The main contents of this paper includes the following aspects:1.Traditional transformation model does not fit for the situation with too large Euler-Angle that may exist in the process of coordinate transformation of airport construction surveying engineering.In view of this situation,this paper proposes a direct numerical methods based on nonlinear least square to establish the transformation relationship between the national coordinate system and the airport coordinate system,which is realized through MATLAB.2.For the case of insufficient or missing national high-level control points in some airport construction in high-elevation mountain areas.This paper uses the GAMIT software,a precise ephemeris solving software to calculate through cosurveying with the International Tracking Station(IGS).And the GAMIT automation baseline processing program is developed based on the Windows operating system according to the characteristics of GAMIT.This program realizes the intelligence of baseline calculate and saves the process of manual operation,which improves the efficiency of data processing,reduces the threshold to start using the GAMIT.3.In view of the problem of vertical control survey in the airport construction at high-elevation mountain areas,the geoid refine technology is applied to the main-grid height measurement in the airport construction with the kriging method in this paper.The accuracy and stability are analyzed in practical engineering projects,and the application possibility that GNSS technology used in the main-grid height measurement in airport construction at high-elevation mountains areas is verified.The accuracy is close to 1cm and is superior to the fourth level.4.There are limitations when determining the relative relations between airports using the traditional method,in this case,this paper proposes using the geodesic based on WGS-84 to replace CGCS2000.The experimental results show that this method can not only meet the accuracy requirements,but also improve the working efficiency greatly with several advantages,such as it's a simple process of surveying indoor or outdoor,it can be surveyed in two or more airports at the same time,and it can be surveyed without the national control points and coordinate transformation.