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11.
HWANG Chenway 《地球空间信息科学学报》2010,13(2):144-149
The quality of altimeter data and ocean tide model is critical to the recovery of coastal gravity anomalies. In this contribution,
three retracking methods (threshold, improved threshold and Beta-5) are investigated with the aim of improving the altimeter
data over a shallow water area. Comparison indicates that the improved threshold is the best retracking method over China
Sea. Two ocean tide models, NAO99b and CSR4.0, are analyzed. Results show that different tide models used in the processing
of altimeter data may result in differences more than 10 mGal in recovered coastal gravity anomalies. Also, NAO99b is more
suitable than CSR4.0 over the shallow water area of China Sea. Finally, gravity anomalies over China Sea are calculated from
retracked Geosat/GM and ERS-1/GM data by least squares collocation. Comparison with shipborne gravimetry data demonstrates
that gravity anomalies from retracked data are significantly superior to those from non-retracked data. Our results have the
same order as the other two altimeter-derived gravity models: Sandwell&Smith(V16) and DNSC08. 相似文献
12.
基于雷达波卫星测高技术,通过数据处理获取华北平原和华东地区的地面沉降数据;优化地球物理参数和环境改正数,利用高精度SRTM模型进行地形坡度改正,通过改进的阈值算法提高测高数据的观测精度。将获取的地面沉降速率与GNSS基准站观测结果进行比较,偏差为-3.4±9.1 mm/a,相关性为0.88。采用阈值法和改进阈值法进行波形重跟踪改正的偏差分别为-3.2±5.5 mm/a和-2.9±4.1 mm/a,相关系数分别为0.94和0.97。实验结果表明,卫星测高可应用于地面沉降监测研究,尤其在缺少GNSS或传统水准监测数据的偏远地区的地面沉降监测中具有重要的研究价值。 相似文献
13.
基于初步研究获得的合成孔径雷达高度计卷积模型,推导获得合成孔径雷达高度计波形关于时间偏移、合成上升时间、信号幅度3个参数偏导数的卷积计算公式,利用数值积分及傅里叶变换实现合成孔径高度计回波模型的重跟踪。在多个单位联合协同下,利用仿真轨道、对流层、电离层及潮汐等模型生成了合成孔径模式下的回波波形。对比表明,仿真生成的合成孔径模式下的回波波形与CryoSat-2卫星SAR模式下的回波波形整体形状一致。利用仿真波形数据进行重跟踪试验,结果表明在20Hz数据条件下(约350m分辨率),合成孔径模式下的重跟踪精度达到5cm,较之传统模式有一定的提高。 相似文献
14.
卫星测高数据监测青海湖水位变化 总被引：3，自引：0，他引：3
为了验证Cryosat-2/SIRAL数据监测湖泊水位的能力,提高其提取湖泊水位变化的精度,以青海湖为研究对象,利用主波峰重心偏移法、主波峰阈值法、主波峰5-β参数法、传统重心偏移法、传统阈值法和传统5-β参数法6种算法对Cryosat-2/SIRAL LRM 1级数据进行波形重跟踪,提取青海湖2010—2015年湖泊水位,对比不同算法获取水位的精度,并结合Envisat/RA-2 GDR数据,延长水位变化时间序列,获得青海湖2002年—2015年的水位变化信息。结果表明,主波峰5-β参数法提取湖泊水位的精度最好,均方根误差为0.093 m;对于GDR产品中LRM模式的3种数据,基于Refined OCOG算法的数据更适合湖泊水位的提取;青海湖2002年—2015年水位整体上涨,水位平均变化趋势为0.112 m/年,年内水位变化呈现明显的季节性。 相似文献
15.
1IntroductionSZ-4spaceborne,launched on30December2002,is the fourth unmanned spaceborne of China.Multimode microwave remote sensor is its primaryload,of which the altimeter mode is the most impor-tant one.During about five months,a large numberofSZ-4altim… 相似文献
16.
中国近岸海域高度计JASON-1测量数据的波形重构算法研究 总被引：3，自引：1，他引：2
卫星雷达高度计的测量数据目前已被广泛应用于各个领域,但高度计在近海的测量数据却一直不可用,一方面是因为高度计在近岸海域的回波波形测量受陆地回波的影响,另一方面是因为一些校正量对近海不准确,如大气湿对流层校正、海洋潮汐校正以及大气高频因数校正等。通过对高度计在近海测量的回波波形进行重构处理,可以缩短近海数据不可用的距离,提高数据的数量和质量。以我国海域及邻近海域(14°~45°N,105°~130°E)为研究区域,采用四种波形重构算法(海洋算法、重力中心偏离算法、冰层算法二和阈值算法)对JASON-1高度计1 a共31个周期的测量波形重新进行了计算,比较了轨道交叉点处升轨和降轨的海面高度异常值以及海面高度值与验潮站的实测水位,结果表明重力中心偏离法比其他三种算法更适合我国近海的测高波形重构:计算结果精度最高,有效数目最多。 相似文献
17.
Surajit Ghosh Praveen Kumar Thakur Vaibhav Garg Subrata Nandy Shivprasad Aggarwal 《Marine Geodesy》2015,38(3):597-613
In the present study, behavior of the SARAL/AltiKa (Satellite with ARgos and ALtiKa) waveforms over Maithon Reservoir (～65 km2 of surface area), Jharkhand, India, has been studied. The estimated water level has been compared with the in situ measurements at hydro-gauging station at the dam site. The problem of minimization of errors in the water level retrieval from AltiKa measurements has been resolved by improvement of the retracking method. A real retracking gate detection algorithm based on statistical analysis harnessing various physical parameters of the waveform has been developed, which has been applied to SARAL/AltiKa waveforms over the Maithon reservoir. Comparing the in-situ measurements with altimetry data (from cycle 1, 19 March 2013 to cycle 12, 8 April 2014) showed that it is crucial to improve the retracking method. Results showed accuracy of water level monitoring increased by nearly 76% by the newly developed waveform retracking algorithm over non-retracked water level. We also compared this new method with the existing ice-1 algorithm and found that with the new method there is improvement of ～27% over ice-1 retracked water level. The correlation coefficient values and root mean square values without retracking, with ice-1 algorithm and with newly developed retracking algorithm were 0.87, 0.91, and 0.95, and 8.12 cm, 2.08 cm, and 1.42 cm, respectively. This shows the proposed retracker performed better than ice-1. The retracking procedure helped in outliers' identification and substitution and with waveform fitting and waveform parameter extraction. This algorithm should have good performance capability for retrieving water level over inland water bodies like Maithon reservoir. 相似文献
18.
长江口EnviSat测高数据的波形分类重构分析 总被引：1，自引：1，他引：0
采用波形分类重构算法处理EnviSat卫星从2002年10月至2010年5月在长江口近岸海域28°N~32°N、121°E~125°E范围内的波形数据。该区域内海洋波形、波形后缘前端出现峰值的波形、波形后缘后端出现峰值的波形、似镜面波形和复杂波形分别占89.03%、2.95%、0.45%、3.31%和4.26%。根据不同的波形类别采用不同波形算法进行波形重构。同时,分析了不同重构算法之间的系统偏差,并据此确定OCOG算法、Threshold算法和子波形算法的最优阈值水平分别为65%、45%和50%。重构结果表明,波形分类重构算法优于其他波形重构算法,能有效改善原始海面高的精度,改善程度在16.62%~53.86%之间。此外,重构后交叉点差值小于重构前的交叉点差值,与轨迹P089、P411形成的交叉点的海面高差值由1m降低到25cm左右,其余交叉点的差值均在2~6cm。 相似文献
19.
Coastal Gravity Anomalies from Retracked Geosat/GM Altimetry: Improvement, Limitation and the Role of Airborne Gravity Data 总被引：6，自引：0，他引：6
Cheinway Hwang Jinyun Guo Xiaoli Deng Hsin-Ying Hsu Yuting Liu 《Journal of Geodesy》2006,80(4):204-216
We process geophysical and waveform data records of the Geosat/GM (geodetic mission) satellite altimeter mission for waveform retracking and applications. An improved threshold retracker is developed. The performances of the Beta-5, threshold and improved threshold retrackers are assessed over waters around Taiwan. The improved threshold retracker outperforms the other two. The improvement in the accuracy of sea surface height (SSH) is investigated according to marine zone and the distance of waters to the shore. The improvement rate increases closer to the land, with the largest improvement rate of about 20% in waters within 10 km of the shore. Over waters around islands and coasts, there are still retracked SSHs with large errors. Least-squares collocation is used to compute gravity anomalies from the Geosat/GM altimeter data. Use of retracked SSHs improves the accuracy of gravity anomalies by about 11%. Adding airborne gravity data further improves the accuracy, especially in the immediate vicinity of the coasts. Tide model errors over coastal waters remain a problem in altimetry applications, even if the waveforms are properly retracked. 相似文献
20.
Geosat／GM波形重跟踪反演中国沿海区域重力异常 总被引：1，自引：1，他引：0
利用Geosat/GM测高波形数据,在中国海域内(117°E～129°E,21°N～41°N)比较了阈值法、Beta5和改进阈值法三种重跟踪算法.分析表明,改进阚值法优于其他两种重跟踪方法.由改进阈值法的测高数据.分别采用最小二乘法(least sqlilare collocation,LSC)和逆Vening-Meinesz(IVM)计算了卫星测高重力异常,并与船测重力数据进行了比较.结果显示,LSC的精度优于IVM.与KMS02和Sandwell & Smith V15两个重力场模型相比较,本文结果在东海优于这两个模型,在台湾海域结果稍差,需要融合ERS-1等其他数据进一步提高精度. 相似文献