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In the fields of space geodetic techniques, such as Global Navigation Satellite System (GNSS), tropospheric zenith hydrostatic delay (ZHD) is chosen as the a priori value of tropospheric total delay. Therefore, the inaccuracy of ZHD will definitely infect parameters like the wet delay and the horizontal gradient of tropospheric delay, accompanied by an indirect influence on the accuracy of geodetic parameters, if not dealt with well at low elevation angles. In fact, however, the most widely used ZHD model currently seems to contain millimetre-level biases from the precise integral method. We explored the bias of traditional ZHD models and analysed the characteristics in different aspects on a global annual scale. It was found that biases differ significantly with season and geographical location, and the difference between the maximum and minimum values exceed 30 mm, which should be fully considered in the field of high-precision measurement. Then, we constructed a global grid correction model, which is named ZHD_crct, based on the meteorological data of year 2020 from ECMWF (European Centre for Medium-Range Weather Forecasts), and it turned out that the bias of traditional model in the current year could be reduced by ~50% when the ZHD_crct was added. When we verified the effect of ZHD_crct on the biases in the next year, it worked almost the same as the former year. The mean absolute biases (MABs) of ZHD will be narrowed within ~0.5 mm for most regions, and the STD (standard deviation) will be within ~0.7 mm. This improvement will be helpful for researches on meteorological phenomena as well.

Affected by factors of measurement errors and so on,the surface mass variation inversion results would be dominated by serious north-to-south stripe noise with using time-variable gravity models directly. Filtering methods must be adopted. Optimal parameters of different filtering methods are determined by taking signal-to-noise ratio maximum as the criterion. On this basis, a new non-isotropic combination filtering method is proposed based on the features of time-variable gravity model spherical harmonic serrors. The new non-isotropic combination filtering method is different from traditional two-steps combination filtering methods. It just performs in one step with combining non-isotropic Gaussian filtering and RMS filtering. The basic idea of the new combination filtering method is to apply larger weights to low-order spherical harmonic coefficients while smaller weights to high-order spherical harmonic coefficients for keeping more signals and suppressing noise. The experiment results show that the new combination filtering method is simple to calculate and stripe noise can be removed effectively. The new combination filtering method improves the signal-to-noise ratio compared with previous filtering methods and traditional two-steps combination filtering methods.

Mapping function errors are usually not taken into consideration, when space geodetic data observed by VLBI, GNSS and some other techniques are utilized to estimate troposphere delay, which could, however, probably bring non-ignorable errors to solutions. After analyzing the variation of mapping function errors with elevation angles based on several-year meteorological data, this paper constructed a model of this error and then proposed a two-step estimation method of troposphere delay with consideration of mapping function errors. The experimental results indicate that the method puted forward by this paper could reduce the slant path delay residuals efficiently and improve the estimation accuracy of wet tropospheric delay to some extent.

Airborne gravimetry is an effective technology to obtain the Earth's gravity field information of land and offing area in high precision and resolution quickly.Downward continuation is one of the key steps in airborne gravimetry data processing,and the quality of continuation results directly influence the further application of surveying data.Based on numerical analysis of the continuation models of traditional least squares method,improved least squares method and Tikhonov regularization method,and according to the basic characteristics of spherical harmonic function,the continuation models of Poisson integral iteration method and improved Poisson integral iteration method were proposed and deduced.For the testing area in this paper,the surveyed airborne and terrestrial gravimetry data prove that the precision of the new continuation models of Poisson integral iteration method and improved Poisson integral iteration method are equal.Compared with the continuation models of traditional least squares method and improved least squares method,of which the precision are improved about 15.26 mGal and 0.21 mGal,respectively.The precision of new continuation models are inferior to Tikhonov regularization method about 0.13 mGal.Therefore,the new continuation models proposed in this paper can not only be used to amend the ill-posed problem of the continuation model introduced by traditional Poisson integral discretization formula,but also be used to suppress the ill-posed problem of the continuation model itself.Therefore,the research achievements can be applied directly in the data processing of our country's airborne scalar and vector gravimetry.

Radial point-mass model method is the disturbance gravity downward continuation in essence, which is an ill-posed problem. In general, the regularization method is an efficient way to get the reliable solution. To solve this problem, the radial point-mass model method is improved by using Helmert variance component estimation with adding spatial constraints from a practical point of view. Taking South America continent as study area, radial point-mass model method with spatial constraints is verified by experimental results. The experiments results show that the condition number of normal equations is decreasing obviously after adding spatial constraints. The inversion results of radial point-mass model method with spatial constraints are consistent with results of other methods. Furthermore, the radial point-mass model method with spatial constraints provides an alternative way to monitor regional surface mass variations by satellite gravimetry.

In accordance with practical needs of a project,the mutual shielding effect between two radio antennas located within some limited area is analyzed in this paper.The concept of the externally connected sphere of an antenna in altazimuth(azimuth-elevation) mount is put forward.A calculation method via numerical integral of the area of a part of spherical crown is given.The mutual shielding effect between the 25 m and 13 m radio telescope at Sheshan is analyzed and estimated.The result is of theoretical reference meanings in the design phase of the project concerning the position selection and height design of the supporting tower of the 13 m antenna.The analytical idea and method can also be used as reference by similar engineering practice.

Known for unique super-high spatial resolution and positioning accuracy, very long baseline interferometry (VLBI) has been a geodetic research hotspot in various countries since late 1970s. The measuring capability of VLBI currently, however, still stays below satisfaction to a number of scientific and engineering fields, which require millimeter-level accuracy. In order to realize the goal of 1 mm positioning accuracy on global scales, the international VLBI service for geodesy and astrometry(IVS)recommended constructing a new generation VLBI observing system, namely VGOS. Starting with subsystems that constitute a VGOS station, this paper introduced the present progress and development trend of VGOS at home and abroad, and finally listed the problems and challenges which still should be faced at present stage.

A relative calibration method used in a novel dual-satellite formation flying altimetry mode is proposed, and a complete formula for calculating relative bias between altimeters is presented. Power spectrum analysis of each correction term in relative bias calculation formula and statistical analysis of differential sequences are respectively conducted with Jason-2 altimetry data. Under the premise that a centimeter level calibration accuracy is ensured, the formula is simplified and error budget is made. The results show that all correction items have low frequency characteristic, and the relative bias error is mainly related to the relative radial orbit error between two satellites, range error, sea state bias as well as the differential geoid height error between two comparison points. As for single overflight, the accuracy of relative bias between two altimeters is about 1.99 cm.

Based on the admittance theory of gravity anomalies, the method of bathymetry prediction was studied in detail in this paper. In frequency domains, the correlation between gravity anomalies and bathymetry was analyzed, which suggests that the wavelength band correlated strongly was in a range of 20—300 km, this band was appropriated to inverse bathymetry by gravity anomalies. Took the Emperor Chain as an example, the uncompensated admittance model and flexural isostatic admittance model were used for researching, respectively, the included parameter of crust thickness and effective elastic thickness were calculated by the isostatic response function. As the down continuation factor was unstable, a high-cut filter was proposed in the inversion procedure to ensure convergence of series. The results showed that, the admittance theory of gravity anomalies can be used effectively in the bathymetry prediction, the predicted result was real and reliable, the relative precision was approximately 6%, which was equal to ETOPO1 model, and the detailed feature of sea floor which was not showed in ETOPO1 model can also be depicted; the precisions were not so well in areas of ocean mountains intensively distributed because of the complexion of the sea floor.

Airborne vector geomagnetic measurement can not only obtain total geomagnetic field strength of geomagnetic field, but also detect the vector information of geomagnetic field, so it is an effective technology to obtain the geomagnetic field information of land and offing area in high precision and resolution quickly. Therefore, this technology has broad application prospect in the domain of aviation, sailing, and spaceflight, especially in the application of self-navigation of geomagnetic matching. The first airborne vector geomagnetic measurement was successfully developed by Xi’an research institute of surveying and mapping and national space science center of Chinese academy of sciences in China. During May-June in 2015, and June-July in 2016, the integration experimentation of the airborne vector geomagnetic measurement was organized by Xi’an Research Institute of Surveying and Mapping on the plain of Inner Mongolia, it included 227 flying surveying lines, and of which the length was about 5000 kilometers, so a great amount of total geomagnetic field strength and vector information of geomagnetic field were obtained. Based on 15 repeated flying surveying lines, 400 crossing points of 20 intersection flying surveying lines in the direction of south-north, east-west, which are in 200m and 700m flying height, the precision evaluation of the airborne vector geomagnetic measurement is accomplished by the comparison of repeated flying surveying lines and crossing points. From the comparison of repeated flying surveying lines, we can get the conclusion that the precision of total geomagnetic field strength on the flying surveying lines in 200m and 700m flying height are 2nT and 1nT, respectively. The precision of three components of the geomagnetic field are between 5nT and 10nT. And from the comparison of crossing points, we can get the conclusion that the precision of total geomagnetic field strength on the flying surveying lines are 1nT, the precision of three components of the geomagnetic field are below 10nT. Therefore, from the data processing of the first airborne vector geomagnetic measurement in China, we can see that the precision of total geomagnetic field strength is about 2nT, and the precision of three components of the geomagnetic field are about 10nT.

In order to solve the problem of deriving the disturbing gravity from satellite altimetry data, the analytical formula of disturbing gravity computed from geoid and vertical deflection are derived. The analytical formula can be used to get global ocean disturbing gravity by using altimetry data. Considering the existing achievements, the two improved quick computation methods which are respectively according to the global and local area are also get based on the one dimensional FFT algorithm. The quick computation methods can get the same results as the analytical computation and improve the computation speed of 20 times. The precise, quick computation methods can avoid the problem of aliasing and edge effects and have the flexible application. The 2.5' resolution of geoid and vertical deflection derived from EGM2008 model are used to compute the global and local ocean disturbing gravity. The results show that the difference between two method is about 0.8×10-5 m/s2, so the disturbing gravity respectively derived from geoid and vertical deflection are consistent. Considering the actual situation, the disturbing gravity derived from vertical deflection still has some advantages.

The systematic error sources for airborne gravimetry are analyzed in detail using the basic mathematical model. The sources can be classified into three types: the first is the observation errors in the parking apron gravity values and the base reading of the airborne gravimeter, the second is the calibration errors of cross-coupling correction, beam scale factor and the scale value, and the third is the modeling errors in the horizontal acceleration correction. The magnitudes of the various systematic errors are discussed and the related compensation methods are proposed. It is indicated that the modeling error of the horizontal acceleration correction (HAC) is one of the largest errors. Analysis of real data demonstrates that the systematic bias between airborne gravity and the ground (or sea) reference value in the Datong, Harbin and Bohai areas are all less than 1×10−5 m·s−2 after compensating the various systematic errors especially the modeling errors of horizontal acceleration correction.

Independent of traditional approach of satellite altimeter calibration, the feasibility of altimeter validation using tide gauge located on solitary island at open sea (TGSI) and deep-ocean bottom pressure recorder (BPR) separately is initially studied. Bias of Jason-3 sea surface height (SSH) and relative SSH bias (△bias) between Jason-2 and Jason-3 is calculated using the data of tide gauge on Harvest oil platform, tide gauge No.1890000 and BPR No.21419. The standard deviations of calculated SSH bias sequence are 3.98 cm, 2.87 cm and 8.61 cm respectively, and △bias (Jason-3-Jason-2) is -3.62±2.17 cm, -2.58±1.97 cm and -2.60±1.30 cm respectively. Comparing to the results reported by foreign calibration sites, the results show that Jason-3 SSH is 3.0 cm lower than that of Jason-2. The selected BPR is appropriate to the calculation of relative SSH bias between Jason-2 and Jason-3, but it is not suitable for calibration or validation of single satellite. TGSI is appropriate to both.