为了对即将发布的新一代全球重力场模型EGM2020(Earth Gravitational Model 2020)在似大地水准面精化上的提升进行评估,通过其试验版的全球重力场模型XGM2019(X Gravitational Model 2019)利用扰动位配合布隆斯公式计算出高程异常的长波...为了对即将发布的新一代全球重力场模型EGM2020(Earth Gravitational Model 2020)在似大地水准面精化上的提升进行评估,通过其试验版的全球重力场模型XGM2019(X Gravitational Model 2019)利用扰动位配合布隆斯公式计算出高程异常的长波项,以评估XGM2019(Earth Gravitational Model 2008)相较于EGM2008(Earth Gravitational Model 2008)在直接转换为正常高精度上的提升;利用"移去-恢复-拟合"法以及顾及由地形起伏变化引起高程异常的短波波分,通过内符合精度和外符合精度来对比其在似大地水准面精度上的提升。以河南省平顶山市某区域的实测数据为例验证了该模型和方法的GPS高程拟合精度。结果表明,在研究区域内使用XGM2019模型在计算高程异常长波精度上相比EGM2008有近1倍的提高,在应用"移去-拟合-恢复"法后两种模型的计算结果比较相近。展开更多
A method is presented to extrapolate a time series of wave data to extreme wave heights. The 15-year time series of deepwater wave data collected for 34 min every hour from 1988 to 2002 in the South Pacific Ocean, Aus...A method is presented to extrapolate a time series of wave data to extreme wave heights. The 15-year time series of deepwater wave data collected for 34 min every hour from 1988 to 2002 in the South Pacific Ocean, Australia, is analyzed to generate a set of storm peak wave heights by use of the Peaks-Over-Threshold method. The probability distribution is calculated by grouping the observod storm peak wave heights into a number of wave height classes and assigning a probability to each wave height class. The observed probability distribution is then fitted to eight different probability distribution functions and found to be fitted best by the Weibull distribution （a = 1.17）, nearly best by the FT-Ⅰ, quite well by the exponential, and poorly by the lognormal function based on the criterion of the sum of squares of the errors, SSE （H）. The effect of the threshold wave height on the estimated extreme wave height is also studied and is found insignificant in this study. The 95 % prediction intervals of the best-fit FT-Ⅰ , exponential and Weibull functions are also derived.展开更多
The height anomaly surface is fitt and the quasi-geoid can be obtained when the height anomaly is determined with the geometric analytic method. Therefore, some mathematical models to fit height anomaly surface using ...The height anomaly surface is fitt and the quasi-geoid can be obtained when the height anomaly is determined with the geometric analytic method. Therefore, some mathematical models to fit height anomaly surface using GPS, leveling and terrain data in a local area, including the polynomial fitting model, the multi-surface function fitting model, the motion surface fitting model and the fitting model of little flexibility deformation of thin board, are given. Then the digital characteristics are analyzed with the curved surface theory. The General curvature and the mean curvature of surface are concluded. The advantage, disadvantage and application of the above models are discussed. The effect of terrain undulation on height anomaly is considered in the surface fitting models. The practical case indicates that these models are of validity and practicability. It is concluded that the above models can give the good fitting results at the centimeter level. But the polynomial fitting model is worse than the other models.展开更多
The Shenzhou -4 spaceborne （SZ -4） altimeter waveforms were processed, and then the significant wave heights （SWH） was retrieved on the basis of waveform fitting and waveform retracking. Waveforms processing inclu...The Shenzhou -4 spaceborne （SZ -4） altimeter waveforms were processed, and then the significant wave heights （SWH） was retrieved on the basis of waveform fitting and waveform retracking. Waveforms processing includes the waveform ls averaging, the elimination of thermal noise and the waveforms normalization. Double peaks were found on each SZ - 4 waveform, and it was pointed out that the region of waveforms with the second peak is abnormal and its effects on the whole waveform in the waveform fit should be taken into consideration. To obtain the width of the waveform leading-edge, a method was proposed to find the starting point of waveform, and the half-power point of waveform was found by retracking the waveform. The normalized wavefornis were fitted with the Haynes model by using the weighting least square fit method. Then the selections of the weighting coefficients and their effects on significant wave hight retrieving were discussed, and the optimal five-region weighting method was proposed. At last, the SWH data of SZ -4 altimeter retrieved by using the proposed method were compared with those of ERS -2 and Jason - 1 altimeter, and it was concluded that the SZ -4 altimeter can detect significant wave height.展开更多
The national benchmarks on islands were mostly established by trigonometric leveling in Korea. This method results in inaccuracy, which is a serious problem in Geoga Grand Bridge construction work that tried to link t...The national benchmarks on islands were mostly established by trigonometric leveling in Korea. This method results in inaccuracy, which is a serious problem in Geoga Grand Bridge construction work that tried to link the mainland and the islands. The Geoga Grand Bridge （Pusan-Geoje fixed link project） was selected as the study area, a huge construction work in Korea that will connect the mainland （Pnsan） and an island （Gecje island）. However, the orthometric heights issued at benchmarks （JINH and GOFJ） were not consistent, because they did not refer to the same zero point, which would make the linking of the sections problematic. This paper introduces the precise local geoidas a vertical datum for the construction area in order to establish a consistent height system. To determine the precise local geoid for the construction area, we firstly developed a precise gravimetric geoid for Korea and its adjoining seas as a whole. This gravimetric geoid was developed by use of all available gravity data, including surface and satellite data on land and on the ocean. The gravimetrie gecid was computed by spherical fast fourier transform with modified Stokes＇ kernels. The remove-restore technique was used to eliminate the terrain effects by use of the RTM reduction and to determine the residual geoid by combining the GGM02S/EGM96 geopotential model, free-air gravity anomalies and high-resolutinn DEM data. Finally, the gravimetric model was fitted to the geoid heights obtained from GPS and tide observations （Ncps/Tiae） by least square coUocatian, to provide the final GPS-consistent local precise geoid model. The post-fit error （std. dev. ） of the final geoid to the NetS/Tide derived from GPS and tide observations was ± 2.2 cm for the construction area. We solved the height inconsistency problem by calculating the orthometric height of the benchmarks and the cnntrol points using the final geoid model. Also, the highly accurate orthometric height was estimated through the GPS/leveling technique by applying the developed local precise geoid. Therefore, the precise local geoid is expected to improve the quality of the construction procedure of the Geoga Grand Bridge.展开更多
文摘为了对即将发布的新一代全球重力场模型EGM2020(Earth Gravitational Model 2020)在似大地水准面精化上的提升进行评估,通过其试验版的全球重力场模型XGM2019(X Gravitational Model 2019)利用扰动位配合布隆斯公式计算出高程异常的长波项,以评估XGM2019(Earth Gravitational Model 2008)相较于EGM2008(Earth Gravitational Model 2008)在直接转换为正常高精度上的提升;利用"移去-恢复-拟合"法以及顾及由地形起伏变化引起高程异常的短波波分,通过内符合精度和外符合精度来对比其在似大地水准面精度上的提升。以河南省平顶山市某区域的实测数据为例验证了该模型和方法的GPS高程拟合精度。结果表明,在研究区域内使用XGM2019模型在计算高程异常长波精度上相比EGM2008有近1倍的提高,在应用"移去-拟合-恢复"法后两种模型的计算结果比较相近。
文摘A method is presented to extrapolate a time series of wave data to extreme wave heights. The 15-year time series of deepwater wave data collected for 34 min every hour from 1988 to 2002 in the South Pacific Ocean, Australia, is analyzed to generate a set of storm peak wave heights by use of the Peaks-Over-Threshold method. The probability distribution is calculated by grouping the observod storm peak wave heights into a number of wave height classes and assigning a probability to each wave height class. The observed probability distribution is then fitted to eight different probability distribution functions and found to be fitted best by the Weibull distribution （a = 1.17）, nearly best by the FT-Ⅰ, quite well by the exponential, and poorly by the lognormal function based on the criterion of the sum of squares of the errors, SSE （H）. The effect of the threshold wave height on the estimated extreme wave height is also studied and is found insignificant in this study. The 95 % prediction intervals of the best-fit FT-Ⅰ , exponential and Weibull functions are also derived.
基金Project (02 -09 -13) supported by Open Research Fund Programof the Key Laboratory of Geospace Environment and Geodesy , Ministryof Education ,China Project (SD2003 -4) supported by Open Research Fund Programof the Key Laboratory of Geomatice Digital Tech-nology ,Shandong Province , China Project supported by FIG Foundation
文摘The height anomaly surface is fitt and the quasi-geoid can be obtained when the height anomaly is determined with the geometric analytic method. Therefore, some mathematical models to fit height anomaly surface using GPS, leveling and terrain data in a local area, including the polynomial fitting model, the multi-surface function fitting model, the motion surface fitting model and the fitting model of little flexibility deformation of thin board, are given. Then the digital characteristics are analyzed with the curved surface theory. The General curvature and the mean curvature of surface are concluded. The advantage, disadvantage and application of the above models are discussed. The effect of terrain undulation on height anomaly is considered in the surface fitting models. The practical case indicates that these models are of validity and practicability. It is concluded that the above models can give the good fitting results at the centimeter level. But the polynomial fitting model is worse than the other models.
文摘The Shenzhou -4 spaceborne （SZ -4） altimeter waveforms were processed, and then the significant wave heights （SWH） was retrieved on the basis of waveform fitting and waveform retracking. Waveforms processing includes the waveform ls averaging, the elimination of thermal noise and the waveforms normalization. Double peaks were found on each SZ - 4 waveform, and it was pointed out that the region of waveforms with the second peak is abnormal and its effects on the whole waveform in the waveform fit should be taken into consideration. To obtain the width of the waveform leading-edge, a method was proposed to find the starting point of waveform, and the half-power point of waveform was found by retracking the waveform. The normalized wavefornis were fitted with the Haynes model by using the weighting least square fit method. Then the selections of the weighting coefficients and their effects on significant wave hight retrieving were discussed, and the optimal five-region weighting method was proposed. At last, the SWH data of SZ -4 altimeter retrieved by using the proposed method were compared with those of ERS -2 and Jason - 1 altimeter, and it was concluded that the SZ -4 altimeter can detect significant wave height.
文摘The national benchmarks on islands were mostly established by trigonometric leveling in Korea. This method results in inaccuracy, which is a serious problem in Geoga Grand Bridge construction work that tried to link the mainland and the islands. The Geoga Grand Bridge （Pusan-Geoje fixed link project） was selected as the study area, a huge construction work in Korea that will connect the mainland （Pnsan） and an island （Gecje island）. However, the orthometric heights issued at benchmarks （JINH and GOFJ） were not consistent, because they did not refer to the same zero point, which would make the linking of the sections problematic. This paper introduces the precise local geoidas a vertical datum for the construction area in order to establish a consistent height system. To determine the precise local geoid for the construction area, we firstly developed a precise gravimetric geoid for Korea and its adjoining seas as a whole. This gravimetric geoid was developed by use of all available gravity data, including surface and satellite data on land and on the ocean. The gravimetrie gecid was computed by spherical fast fourier transform with modified Stokes＇ kernels. The remove-restore technique was used to eliminate the terrain effects by use of the RTM reduction and to determine the residual geoid by combining the GGM02S/EGM96 geopotential model, free-air gravity anomalies and high-resolutinn DEM data. Finally, the gravimetric model was fitted to the geoid heights obtained from GPS and tide observations （Ncps/Tiae） by least square coUocatian, to provide the final GPS-consistent local precise geoid model. The post-fit error （std. dev. ） of the final geoid to the NetS/Tide derived from GPS and tide observations was ± 2.2 cm for the construction area. We solved the height inconsistency problem by calculating the orthometric height of the benchmarks and the cnntrol points using the final geoid model. Also, the highly accurate orthometric height was estimated through the GPS/leveling technique by applying the developed local precise geoid. Therefore, the precise local geoid is expected to improve the quality of the construction procedure of the Geoga Grand Bridge.
