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Using the point mass fit method, the position, size and other parameters of the point mass source are inversed by fitting the shipborne gravity anomaly data with the minimum variance between the point mass model and observed value.Avoiding the instability posed by the point mass method, the shipborne residual gravity anomalies are calculated by using these parameters based on the idea of remove-restore technique.Shipborne gravity residuals can be obtained by minusing the gravity anomaly in the track line.The altimetric residual gravity data are also obtained by using the similar method.Weighted the two residual gravity anomaly by the minimum curvature gridding method, and restored the model gravity anomaly calculated by the point mass size, depth and other parameters, then realized the satellite altimetry and shipborne gravity data fusion.The mean bias is 1~2 mGal and the root mean square is about 4 mGal, which is verified by the international shipborne gravity measurement data.The proposed method can be used as a reference for processing the various gravity data fusion in coastal zone and for satellite gravity downward continuation problem.

Based on the remove-restore method, the GRACE satellite gravity data are used to study the variation of terrestrial water storage from January 2003 to June 2014 in North China Plain. A method for calculating the scale factor considered seasonal influence is proposed to reduce the GRACE post-processing error. The results obtained by the proposed method are compared with those from hydrological model and the precipitation model. The results indicate that serious drought occurred in North China Plain before 2008, and the terrestrial water and surface water decrease at the rate of (-7.9±2.4)mm/a and (-7.3±2.8)mm/a respectively while the groundwater decrease only at the rate of (-0.6±1.4)mm/a. However since 2008, the terrestrial water and surface water show an upward trend of (4.3±1.3)mm/a and (10.9±2.1)mm/a respectively.On the other hand, the over-exploitation of groundwater began to aggravate, and groundwater level showed a downward trend of (-6.5±1.2)mm/a, but the descent rate was reduced at the rate of -0.9 mm/a2.During the study period, the terrestrial water, surface water and groundwater storage in North China Plain show a trend of (-2.0±0.6)mm/a, (2.9±0.7)mm/a and (-4.8±0.7)mm/a respectively.Finally, the phenomenon of GRACE lagging behind precipitation is analyzed using cross-wavelet spectrum.Research revealed that the two most crucial factors influencing the water storage variation in North China Plain are precipitation and groundwater exploitation.

Based on the definition of height system, the gravitational equipotential property of height datum surface is discussed in this paper, differences of the heights at ground points that defined in different height systems are tested and analyzed as well. A new method for replacing leveling using GNSS is proposed to ensure the consistency between GNSS replacing leveling and spirit leveling at mm accuracy level. The main conclusions include:①For determining normal height at centimeter accuracy level, the datum surface of normal height should be the geoid. The 1985 national height datum of China adopts normal height system, its datum surface is the geoid passing the Qingdao zero point.②The surface of equi-orthometric height in the near earth space is parallel to the geoid. The combination of GNSS precise positioning and geoid model can be directly used for orthometric height determination. However, the normal height system is more advantageous for describing the terrain and relief.③Based on the proposed method of GNSS replacing leveling, the errors in geodetic height affect more on normal height result than the errors of geoid model, the former is about 1.5 times of the latter.

The Ku band backscatter coefficients data have been extracted since 2002.5 to 2005.5 from Topex/Poseidon(T/P)GDR-M and Envisat OPR datasets. Based on the continuous tension spline curve gridding method, the time series gridding data was obtained. Then the two different backscatter coefficients time series were compared. Carefully analysis and discussion on the spatial distribution characteristic of the backscattering coefficients in Inner Mongolia plateau, North China Plain, Northeast China Plain, the Qinghai Tibet Plateau, the Yunnan Guizhou Plateau, the Loess Plateau, the Yangtze River Plain indicate that both technologies can be used for monitoring natural disasters and potential environmental change of China and providing decision support for monitoring time series for land cover change.