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With the development of Global Navigation Satellite Systems (GNSS), the multipath effect that was once regarded as one error source has been proven can be used to monitor reflecting surface parameters such as water level, snow depth, vegetation water content, and soil moisture using a technology named GNSS-interferometry reflectomety (GNSS-IR). In order to expand monitoring objects and applications of GNSS-IR, this paper proposed the theory and method to retrieve wind speed using ground-based GNSS-IR. The theory includes the signal-to-noise ratio (SNR) multipath oscillation theory, the scattering model theory, and wave spectrum theory. This paper simulated the mathematical model between the SNR cutoff elevation angle and the wind speed, and used the wavelet analysis to extract SNR cutoff elevation angle and a unified method to unify reference of cutoff elevation angle. Data of HKQT station, located in Hong Kong, during the period of "Mangkhut" and "Hato" were used. The results showed that the variations of GPS L5 SNR cutoff elevation angles had a good corresponding relationship with the measured wind speeds, and the correlation coefficient reached 70%~85%. Also, the variations of cutoff elevation angles can describe the change of wind speed from low wind speed to high wind speed and there was a specific mathematical relationship between them. Finally, this paper discussed two difficulties to overcome in the GNSS-IR wind speed retrieval technology.

The ionospheric scintillation, as one of the astronomical disasters occurring frequently in Arctic regions, poses great challenges to GNSS positioning navigation and timing (PNT) services. This calls for an urgent need in studying and effectively monitoring the scintillation to overcome its adverse impact. With the capability of high frequency sampling, ionospheric scintillation monitoring receivers (ISMR) are usually required to monitor the ionospheric scintillation, but the distribution of ISMR restricts the comprehensive monitoring in larger areas (such as the Arctic region). Therefore, based on GNSS observations with 1 Hz sampling, this paper studies the relevant empirical parameters and methods of extracting the ionospheric scintillation signal from the carrier phase observations by using geodetic detrending, precise point positioning and wavelet transform techniques, to construct a new phase scintillation index, which can be used to monitor the ionospheric scintillation. Its effectiveness and accuracy are verified by 188-day observations from 11 stations provided by the Canadian High Arctic Ionospheric Network (CHAIN). The results show that, compared with the commonly used ROTI index, both the scintillation index proposed in this paper and ROTI can effectively detect the occurrence of ionospheric scintillation, but the scintillation index proposed in this paper has a better correlation with the phase scintillation index given by ISMR, especially during periods with strong ionospheric scintillation, indicating that the proposed scintillation index has better ionospheric scintillation monitoring capability.

Seafloor classification is of great significance for the development and utilization of marine resources and marine scientific research. At present, multibeam detection is one of the effective methods to achieve large-scale seafloor classification. Seafloor classification is usually based on the angular response (AR) features and backscatter image features extracted by using multibeam backscatter. Because the feature source is relatively single and classifier structure is simple, the classification accuracy is often not high. This paper proposes a seafloor classification method based on convolutional neural networks (CNN). In addition to backscatter features, bathymetry features are also used to classify. The feature vectors are converted into waveform maps, and then input to the convolutional neural network for training and classification. The experiment compares different feature combination models and four conventional classifiers: BP network, support vector machine (SVM), k-nearest neighbor (KNN), and random forest (RF). The overall classification accuracy of the experiment reaches 94.86%, the kappa coefficient up to 0.93, and it takes 1 min 25 s. The accuracy has obvious advantages and the efficiency is relatively high. This method can effectively obtain the seafloor information in two different data types, give full play to the characteristics of convolutional neural network weight sharing, high efficiency, and achieve high-resolution seafloor classification. This paper provides a reference for the seafloor classification based on multibeam.

For the determination of the smoothing factor (also known as the regularization parameter) in the co-seismic slip distribution inversion, the compromise curve between the model roughness and the data fitting residual is generally used to determine (in order to distinguish the method proposed in this paper, the method is called "L curve" according to its shape). Based on the L-curve, the eclectic intersection curve as a new method are proposed to determine the smoothing factor in this paper. The results of the simulated experiment show that the inversion accuracy of the parameters of the seismic slip distribution with the smoothing factor determined by the eclectic intersection curve method is better than that of the L curve method. Moreover, the eclectic intersection curve method and the L curve method are used to determine the smoothing factor of L'Aquila and Taiwan Meinong earthquake slip distribution inversion respectively, and the inversion results are compared and analyzed. The analysis results show that the L'Aquila and Meinong of Taiwan actual earthquake slip distribution results are in the range of other scholars at home and abroad, and compared with the L curve method, the eclectic intersection curve method has advantages of high computation efficiency, no need to depend on data fitting degree and more appropriate of smoothing factor and so on.

The research and modeling of nonlinear variations of GPS stations coordinates are effective ways to weaken nonlinear motion of the stations. However,due to the diversity and complexity of nonlinear variations of stations' coordinates,the theoretical correction model contained multiple mechanisms has not been established to weaken the nonlinear motion of GPS stations.In this paper,global distribution regularity of annual terms of vertical coordinates of stations was discovered based on the measured vertical coordinates residuals of nearly 500 GPS stations,two statistical correction models of annual variations based on measured data were respectively constructed for the northern and southern hemispheres.The experiments show that the statistical correction model proposed in this paper can weaken 30%~50% vertical coordinate residuals of most GPS stations in the world.

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.

In general,ionosphere-free model and uncombined model are applied for GNSS precise point positioning (PPP).This paper detailed analyzes the correlation of different parameters of each model,and deducevarious PPP functional model by means of parameterization methods.And uncombined PPP with ionospheric parameter constrains i.e.ionosphere-weighted model can fasten PPP convergence effectively.This paper takes advantage of GPS-only and GPS and BDS combination dataset as example for positioning in different PPP models.In the perspective of positioning accuracy and convergence time,positioning performance are detailed analyzed in both static PPP and simulated dynamic PPP modes.The results demonstrate that GPS-only has the similar accuracy with GPS+BDS combination,and both ionosphere-free model and uncombined model static PPP can achieve the positioning accuracy of millimeter to centimeter level,while the horizontal positioning accuracy of dynamic PPP is superior to 3 cm and the vertical positioning accuracy is superior to 5 cm.In terms of convergence time,ionosphere-free model is superior to uncombined model,and the convergence time of ionosphere-weighted model is the shortest.Compared to the ionosphere-free model,the ionosphere-weighted model can decrease about 15% convergence time,while it can decrease about 34% convergence time compared to the uncombined model in the dynamic positioning.

In the process of dealing with multi-beam bathymetry data by least squares collocation, the quadric curved mathematical model of trend term can not express accurately the whole variation trend of seafloor topography in general. Moreover, the covariance function estimated by general method is incapable of accurately expressing statistical characteristics with the multi-beam bathymetry data contains gross errors or outliers. So the iterative algorithm of robust least squares collocation is proposed in this paper. Firstly, the initial weight matrix of observations and the initial parameters of covariance function are both given in this method, then the trend term is fitted by polyhedral function and equivalent weights scheme is applied into robust estimation in this method. Finally, the robust parameters of covariance function and solutions of least squares collocation are iteratively calculated. The experimental results show that the method proposed in this paper can express well the whole variation trend of seafloor topography and overcome the effect of gross error or outlier in multi-beam bathymetry data to a certain extent. Compared with the conventional robust method, the proposed method in this paper more effectively probes the outliers in bathymetry data with the robust and better predicted results.

Real-time high-precise satellite orbit and clock products are needed in real-time GNSS precise point positioning (PPP). In this paper, Estimation model and strategy of multi-GNSS precise satellite clock integrated resolving are researched and BeiDou/GPS real-time precise clock integrated estimation algorithm is realized by filter. Real-time simulation test results show: the STD accuracy of BeiDou/GPS real-time clock estimated in this paper compared to GFZ multi-GNSS precise clock(GBM) is about 0.15ns; horizontal accuracy after convergence of GPS kinematic PPP using simulation real-time clock products estimated in this paper is better than 5cm and vertical accuracy is better than 10cm, respectively; in BeiDou kinematic PPP test, horizontal and vertical accuracy results are same as the results using GFZ multi-GNSS precise clock(GBM) products, and the decimeter positioning can be realized.

The lack of an effective accuracy assessment method of geoid is a key problem in the modernization of height datum and its application. In this paper, according to the error characteristics of GNSS-leveling height anomaly and gravity field in frequency domain, the technical requirements for the fusion of GNSS-leveling and gravity height anomaly are studied. Furthermore, a method of error expression and accuracy evaluation of geoid is proposed. Through the example test and analysis, the main conclusions are as follows: ①The accuracy of the fused height anomaly should be expressed by the error curve of height anomaly difference varying with the distance. ②For accuracy assessment of quasigeoid, two error indicators and two error curves are recommended, namely, the error of gravity height anomaly difference, the internal error of the fused height anomaly, the error curve of the fused height anomaly difference and the error curve of GNSS-levelling height anomaly difference. ③When the distance between two terrestrial points is close to or less than the average distance between GNSS leveling points, GNSS-levelling height anomaly plays a major role in the contribution of the fused height anomaly. ④The accuracy of the fused height anomaly in large scale is mainly controlled by gravity height anomaly.

With the increasing number of high orbit spacecraft, the use of high orbit GNSS technology to a certain extent avoids the limitations of traditional ground-based measurement and orbit determination, reduces the operation burden and maintenance cost of ground-based measurement and communication, and improves the autonomous navigation ability and orbit measurement accuracy of the satellite platform. Therefore, GNSS technology has significant research significance and application value for high earth orbit spacecraft. In this paper, the technology development of GNSS used in high orbit spacecraft is reviewed. Compared with low orbit spacecraft, the characteristics of GNSS in high orbit space are analyzed. From the three aspects of high orbit GNSS availability, on orbit technology verification and high sensitive receiver technology, the characteristics and development of high orbit GNSS autonomous navigation technology are summarized. The new tasks of high orbit post precise orbit determination and formation satellite relative navigation are analyzed. From the perspective of the future development of high orbit spacecraft, the future research prospect of high orbit GNSS technology is given.

In order to solve the problem that there may be a big difference between the traditional method of water level correction using distance interpolation to calculate the tidal time difference (TTD) of the stations to be determined and the actual situation, this paper puts forward a method of water level correction using astronomical tide to directly calculate the tidal time difference between stations, studies the difference and variation of the tidal time system between astronomical tide and the measured water level of some coastal stations in China, and analyzes the deviation magnitude of the tidal time difference between two groups of adjacent stations with astronomical tide determined by different tidal numbers instead of the measured water level. Using tide gauge stations along the Yellow Sea and Beibu Gulf, the experiment of astronomical tide time difference water level correction is designed, and the effect of the traditional method and astronomical tide time difference method is compared. The experiment and analysis show that using astronomical tide to calculate the tidal time difference is closer to the measured tidal time difference than the traditional method, and the median error of the correction result of the 8 tidal constituents is controlled within 5 cm, nearly double that of the traditional method, realizing the improvement of the traditional method and proving the feasibility of using astronomical tide to correct the water level of the time difference method.

By using the theory of infinite series and the Lagrange inversion theorem, the infinite expansions of the auxiliary latitudes in geodesy and cartography with respect to the geodetic latitude are given, which are the power series of the first eccentricity of the reference ellipsoid. The inverse solutions of the isometric and the conformal latitudes can be obtained from the recurrences of a number of known coefficients. The forward expansion of the conformal latitude is proposed on the basis of the Taylor expansion of the Gudermannian function, and the forward expansion of the rectifying latitude is given in which the coefficient can be expressed as a explicit determinant by the division of power series. Compared the coefficients of the auxiliary latitudes expansions at order e0 to e40 with the results by the computer algebra system Mathematica and the corresponding cost time, the algorithm of this paper is verified to be correct and fast. By taking CGCS2000 reference ellipsoid, the numerical experiment is made for the expansions and then the correctness is further proved.

It is necessary to calculate the direct effect on gravity and the indirect effects on the geoid and quasi-geoid when reducing the topography based on Helmert's second condensation method for solving boundary value problems. The traditional integration algorithms for the near-zone direct and indirect topographic effects arein the double integral form and give some approximate errors when taking the integral kernel at the center of the grid as the average of the grid integral kernel. Furthermore, the traditional integral algorithms for the direct and indirect effects have singularity in the innermost area, which increases the computational complexity. In this paper, the prism formulae of the near-zone direct and indirect effects are deduced, which improves the calculation accuracy on the one hand and simplifies the computation process by removing the singularity in the innermost area on the other hand. To overcome the planar approximation error of the prism models, the curvature of the earth can be taken into account. Finally, experimental results show that the prism algorithm for the topographic effect considering the earth's curvature is recommended when a high-accuracy geoid/quasi-geoid is required.

Determining the vertical deviation for a local height datum relative to the geoid is an important approach to the unification of the Global Vertical Datum. In this paper, we aim at direct determination of the vertical deviation for China Height Datum with the coordinates of Dagang Tidal Gauge. First, the principles for determination of the vertical deviation with the coordinates of Dagang Tidal Gauge are introduced. Then the methods and the processes for measuring and calculating the coordinates of Dagang Tidal Gauge are elaborated. Next EGM2008 and EIGEN-6C4 models are used to calculate the gravity potential with the coordinates of Dagang Tidal Gauge, and the results are compared with those obtained with GPS/Leveling data. It is found that the gravity potential obtained from EGM2008 model is more reliable than that from EIGEN-6C4 model, and the vertical deviation for China Height Datum with the coordinates of Dagang Tidal Gauge is 0.344 m, which is 0.006 m smaller than that with GPS/leveling data.

Backscatter strength angular response embodies the seafloor substrates classification, which are the important data sources for multibeam seafloor classification. At present, multibeam seafloor classification mainly extract mean backscatter strength angular response or sonar image without considering the relevant information of two aspects. This paper comprehensively analyzes backscatter strength angular response and probability distribution of backscatter strength, portraits 3D histogram, and proposes ways of seafloor classification based on 3D histogram of backscatter strength. Results show that the method can directly express different numbers of seafloor classification within multibeam swath, effectively judge the boundaries and realize the fast identification of different seafloor substrates.

This paper briefly analyzes the basic development and technical situation of oceanic spatial information datum, reviews the main processes of oceanic vertical datum and correlative oceanic tidal study, such as improvement and perfect methods of determining tidal station vertical datum, realizing form of vertical datum controlled by tidal station, effect on maintaining vertical datum by long-term tidal station, oceanic tidal model establishing, and also construction and transformation of tidal datum, and then forecasts the key development directions of oceanic spatial information datum on high-accuracy marine position service, vertical datum and the transferring model refinement and spatial datum application.

The exploration of deep internal structure and internal dynamics of the earth has always been a hot topic in the field of basic geoscience research.Traditional approach relies mainly on seismic technology. However, in recent decades, the innovation of modern gravity observation technology (especially the successful application of high-precision superconducting gravity technology) makes it possible to detect the earth's internal dynamics and physical information. In this paper, we summarize the research progress of Chinese group in detecting the earth's free oscillation, free core nutation, inner core translational oscillation, tidal model and polar tide and the internal structure by using modern high-precision gravity technology in recent years.

The coefficient matrix (Green matrix) is composed of surface point offset caused by unit slip of sub-fault patches. The elements of the coefficient matrix are related to the location, geometry of rupture surface, assumption of model and other factors. In this paper, we attempted to consider the Green'function matrix (coefficient matrix) errors in order to compensate for the effects of above-mentioned factors to some extent. The total least squares (TLS) method, which both errors of coefficient matrix and observation vector are considered, is proposed for fault slip inversion. So we dealt with the errors in both of coefficient matrix and observation at same time. And by analysis of the relations between observation vector and coefficient matrix elements, we obtained the covariance matrix of coefficient matrix elements and observation vector. Considering the coefficient matrix was ill-posed, we used the second-order Laplace smoothing to constrain the slip parameters each other, then we used the regularized total least squares method to estimate slip distribution. the total least squares (TLS)slip inversion method was applied to simulate oblique fault event and Mw6.3 earthquake occurred in L'Aquila (central Italy) on April 6, 2009, respectively. To L'Aquila earthquake, the results by total least squares method indicate that the inverted geodetic moment is 3.63×1018 N·m (Mw6.34). With a maximum slip of 0.95 m, and a average rake of -96.4°, the main slip occurred at depth of 4 km-15 km. The difference of slip distribution solutions between total least squares and least squares method is less than 10-4 order.

Ionospheric delay is a major problem in the process of ambiguity resolution over medium and long baselines that the time consuming is barely satisfactory and the success rate is not high. This paper proposes a new ambiguity resolution method which combines the RNSS and RDSS observations of BeiDou to reduce the ionospheric delay. Firstly, two optical virtual observations with small total noise level and ionospheric delay coefficient are selected by analyzing the RNSS and RDSS combination signals. Then, the NL integers of GEO are solved using geometry-independent and ionosphere-free model which are formed by new virtual observations. Finally, the NL integers of non-GEO are solved with known GEO NL integers. This method is verified using simulated data. Test results show that, the new method has higher success rate and less consuming time compared with traditional method.

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.

GNSS precise point positioning (PPP) has become the research hotspot in the most recent years due to its capability of obtaining precise position with single receiver. Usually, three models are used in PPP, that is,uncombined model, Uofc model and ionosphere-free combination model. The relationships between the these models are described in detail in this paper. On the one hand, it is clarified that the uncombined model is equivalent to the Uofc model and both of them are better than the ionosphere-free model in the sense of ambiguity resolution. On the other hand, in comparison with the Uofc model that eliminates the ionosphere delay by using the equivalence principle, the uncombined model that takes the ionosphere delay as the parameter has its advantage that it can provide the users with the prior constrained conditions for the ionosphere. As a result, the model can be converted to the ionosphere-weighted model easily. In the circumstance of fixing the wide-lane, when comparing with the ionosphere-free model by using ambiguity dilution of precision (ADOP) from the aspect of fixing ambiguity, Uofc model has many advantages such as small noise, origin information preserving etc.,while the ionosphere-weighted model can improve the ambiguity resolution significantly when the high precise prior ionosphere information is available.

In order to evade the ill-posedness of downward continuation for airborne gravity data using traditional inverse Poisson integral, in a recent published article,a practical downward continuation method of airborne gravity data was used for the sea surveying areas using the differential conception in navigation and location for reference, in which the continuation corrections are calculated using ultra-high-degree geopotential model. In this paper, we continue using the same idea and develop the method to the application for land surveying areas. It suggests that terrain Information can be used to improve the calculated accuracy of continuation correction from geopotential model. The differential of local topographic corrections on flying height and corresponding ground point is added to the continuation correction from geopotential model, and it makes up the total continuation correction. It is ultimately realized to continue airborne gravity measurements to the ground in full frequency extension. EGM2008 geopotential model, ground gravity data and digital elevation model in high resolution are used as a case study to prove the efficiency of the new method.

Based on a detailed analysis of the Slepian function, the advantages and disadvantages of the application of the Slepian function in computing lunar local gravity model, local power spectrum combined with the CEGM02 model and local admittance and correlation based on CEGM02, SGM150j, LP150Q and GRAIL660 were analyzed in this paper. It turns out that the local orthogonal Slepian function shows obvious advantages in modeling lunar local gravity field. In the application of power spectrum, the method of Slepian model shows a much wider, credible and reliable bandwidth but brings greater uncertainty in high degrees with the abnormal signal on the cap edge. On the contrary, the local power spectrum curve of Slepian window reflects the relationship between local gravity and the whole moon, but the spectral curve shows a narrow reliable bandwidth and significant errors in low degrees. Local admittance and correlation of four gravity models shows small difference in low orders but obvious difference as the orders get higher.

A kind of single-frequency precise point positioning (PPP) algorithm based on the raw observations is presented in this paper. By this algorithm, the ionospheric delays were corrected efficiently by means of adding the ionospheric delay prior information and the virtual observation equations with the spatial and temporal constraints, and they were estimated as the unknown parameters simultaneously with other positioning parameters. Then, a dataset of 178 International GNSS Service (IGS) stations at day 72 in 2012 was used to evaluate the convergence speed, the positioning accuracy and the accuracy of the retrieved ionospheric VTEC. The series of results have shown that the convergence speed and stability of the new algorithm are much better than the traditional PPP algorithm, and the positioning accuracy of about 2-3 cm and 2-3 dm can be achieved respectively for static and kinematic positioning with the single-frequency observations' daily solution. The average bias of ionospheric total electron content retrieved by the single-frequency PPP and dual-frequency PPP is less than 5 TECU. So the ionospheric total electron content can be used as a kind of auxiliary products in GPS positioning.