共查询到20条相似文献，搜索用时 15 毫秒
1.
A kinematic GPS methodology for sea surface mapping,Vanuatu 总被引：1，自引：0，他引：1
Marie-Noelle Bouin Valérie Ballu Stéphane Calmant Jean-Michel Boré Eric Folcher Jérôme Ammann 《Journal of Geodesy》2009,83(12):1203-1217
During the past few decades, satellite altimetry has brought tremendous new knowledge about the spatial and temporal variations
of sea surface heights over the Earth’s oceans. However, the precision is limited over short wavelengths and in coastal areas,
and other methods such as kinematic GPS may be needed to fill in this information. We present kinematic GPS work aimed at
mapping the sea surface height, with special attention to the precision one can expect. Active marine subduction zones, like
the Vanuatu archipelago, may present short wavelength, high amplitude undulations of the sea surface height that are difficult
to map with satellite altimetry. This paper presents the methodology used around Santo Island, in Vanuatu, to obtain a well-resolved
local sea surface map with a precision of 5–15 cm limited by the sea conditions and the distance from the coastal reference
station. We present the results of three campaigns in 2004, 2006 and 2007. Careful observation of the ship behaviour along
the surveys as well as simultaneous recording of the ship attitude variations is mandatory to obtain reliable results. We
show that the ship GPS antenna height varies with the ship’s velocity and we suggest a method to correct this effect. The
final precision is estimated using the crossover differences method. 相似文献
2.
利用卫星测高资料推求西北太平洋海域的海洋大地水准面 总被引：3，自引：0，他引：3
本文根据卫星测高数据和海面动力地形资料，绘制了不相上下北太平洋海域局部大地水准面的精细结构图，对解决卫星测高技术中大地水准面积和海面地形的可分性问题作了初步尝试。 相似文献
3.
Analysis of some systematic errors affecting altimeter-derived sea surface gradient with application to geoid determination over Taiwan 总被引：3，自引：1，他引：3
C. Hwang 《Journal of Geodesy》1997,71(2):113-130
This paper analyzes several systematic errors affecting sea surface gradients derived from Seasat, Geosat/ERM, Geosat/GM,
ERS-1/35d, ERS-1/GM and TOPEX/POSEIDON altimetry. Considering the data noises, the conclusion is: (1) only Seasat needs to
correct for the non-geocentricity induced error, (2) only Seasat and Geosat/GM need to correct for the one cycle per revolution
error, (3) only Seasat, ERS-1/GM and Geosat/GM need to correct for the tide model error; over shallow waters it is suggested
to use a local tide model not solely from altimetry. The effects of the sea surface topography on gravity and geoid computations
from altimetry are significant over areas with major oceanographic phenomena. In conclusion, sea surface gradient is a better
data type than sea surface height. Sea surface gradients from altimetry, land gravity anomalies, ship gravity anomalies and
elevation data were then used to calculate the geoid over Taiwan by least-squares collocation. The inclusion of sea surface
gradients improves the geoid prediction by 27% when comparing the GPS-derived and the predicted geoidal heights, and by 30%
when comparing the observed and the geoid-derived deflections of the vertical. The predicted geoid along coastal areas is
accurate to 2 cm and can help GPS to do the third-order leveling.
Received 22 January 1996; Accepted 13 September 1996 相似文献
4.
本文利用卫星测高、GRACE与温盐数据监测2003-2014年红海海平面变化,并分析了蒸发降水以及亚丁湾-红海质量交换对红海质量变化的影响。红海地区单一的温盐数据存在覆盖不全或质量不佳的问题,综合CORA、SODA与ORAS4温盐数据估算结果得到平均比容海平面变化,以改善比容信号的精度。针对GRACE数据处理过程中截断与空间平滑滤波引起的泄漏误差,提出改进尺度因子纠正泄漏误差,利用卫星测高数据进行模拟实验验证了改进尺度因子的有效性。利用传统尺度因子和改进尺度因子反演的红海质量变化周年振幅分别为16.1±1.3 cm和20.5±1.7 cm,利用卫星测高和温盐数据估算的质量变化周年振幅为20.2±1.0 cm,表明改进尺度因子可有效减小泄漏误差的影响,改善GRACE模型反演红海质量变化的精度。卫星测高、GRACE卫星重力数据以及平均温盐数据具有较好的一致性,联合GRACE和温盐数据估算的红海综合海平面变化周年振幅为16.6±1.7 cm,与卫星测高估算的总海平面变化周年振幅(16.2±0.9 cm)基本一致,表明多源数据可构成完整的红海海平面监测手段。相比于降水-蒸发作用,红海质量变化受红海与亚丁湾的海水质量交换的影响更为显著,其主导了红海质量的季节性变化。 相似文献
5.
The determination of local geoid models has traditionally been carried out on land and at sea using gravity anomaly and satellite
altimetry data, while it will be aided by the data expected from satellite missions such as those from the Gravity field and
steady-state ocean circulation explorer (GOCE). To assess the performance of heterogeneous data combination to local geoid
determination, simulated data for the central Mediterranean Sea are analyzed. These data include marine and land gravity anomalies,
altimetric sea surface heights, and GOCE observations processed with the space-wise approach. A spectral analysis of the aforementioned
data shows their complementary character. GOCE data cover long wavelengths and account for the lack of such information from
gravity anomalies. This is exploited for the estimation of local covariance function models, where it is seen that models
computed with GOCE data and gravity anomaly empirical covariance functions perform better than models computed without GOCE
data. The geoid is estimated by different data combinations and the results show that GOCE data improve the solutions for
areas covered poorly with other data types, while also accounting for any long wavelength errors of the adopted reference
model that exist even when the ground gravity data are dense. At sea, the altimetric data provide the dominant geoid information.
However, the geoid accuracy is sensitive to orbit calibration errors and unmodeled sea surface topography (SST) effects. If
such effects are present, the combination of GOCE and gravity anomaly data can improve the geoid accuracy. The present work
also presents results from simulations for the recovery of the stationary SST, which show that the combination of geoid heights
obtained from a spherical harmonic geopotential model derived from GOCE with satellite altimetry data can provide SST models
with some centimeters of error. However, combining data from GOCE with gravity anomalies in a collocation approach can result
in the estimation of a higher resolution geoid, more suitable for high resolution mean dynamic SST modeling. Such simulations
can be performed toward the development and evaluation of SST recovery methods. 相似文献
6.
In the linear estimation problem associated with an experiment that is exactly repeated a number of times, the estimation
parameters may naturally be partitioned into two groups, those that are common to all repetitions, and those that are particular
to each repeat experiment. We derive least-squares solutions that minimise in norm either group of parameters, as also the
trace of the corresponding covariance matrix. These solutions are applied to the station adjustment of triangulation surveying,
and to the estimation problem of satellite radar altimetry: to estimate simultaneously mean sea surface heights and residual
radial orbit errors, while minimising the norm of either group of parameters. This altimetry problem is considered in the
cases of collinear, local crossover and global crossover data.
Received: 6 January 1997 / Accepted: 21 December 1998 相似文献
7.
This paper demonstrates the use of moderate resolution imaging spectro-radiometer (MODIS) data for fish forecasting mapping of seasonal spatial distribution of sea surface salinity (SSS), temperature (SST) and chlorophyll-a in the ocean waters off the coast of Semporna, Malaysia. Multi-linear regression analysis was performed to estimate SSS and the Brown and Minnet algorithm was used for the SST. The extracted parameters were validated using in situ measurement taken with Hydro-Lab equipment. The extracted parameters from MODIS images reveal the signature values which establish the relationships between these parameters, and thus delineating the potential fish zonation (PFZ) map. These developed models will help for accurate monitoring of large coverage areas at low cost and within short period of time. Furthermore, such models will allow the prediction of the total fish catch in different seasons, thus contributing to fish industry management and marketing. This research recommends the use of PFZ map for mass scale fish harvesting in short time for larger areas. Finally, the research has developed a potential fish zone model amalgamating all the above parameters. The PFZ mapping was carried out off the coast of Semporna, Sabah as there were sufficient fish catch data for accuracy assessment. The R was computed as 0.93 and the higher fish catch areas have coincided very well with the higher PFZ values, meaning the tool is ready for use for operational near real-time fish forecasting. 相似文献
8.
Mean sea surface heights and residual radial orbit errors are estimated simultaneously in a single global crossover adjustment
of multiple cycles of satellite altimetry data. The rank defect inherent in the estimation problem is explicitly identified
and treated in various ways to give solutions that minimise (in norm) either orbit errors or mean sea surface heights. The
rank defect gives rise to geographically correlated orbit error, consisting of those components of the orbit error or those
components of the map of sea surface heights which fall within the nullspace of the estimation problem and which cannot be
distinguished as orbit error or ocean signal. We show that, in the case of Topex/Poseidon data, the geographically correlated error consists largely of long-wavelength and long-period sea surface fluctuations, which
in the past has often been assigned as orbit error.
Received 11 September 1995; Accepted 2 September 1996 相似文献
9.
威德尔海异常是西南极沿海地区在夏季出现的电离层异常现象。本文用西南极地区的GPS跟踪站数据和测高卫星Jason-2数据,分别提取了陆地和海洋地区大范围的电离层TEC参数。GPS反演结果的优势是获取测站上空高精度的TEC时间序列,测高反演的结果整体与GPS的结果精度相当,虽然测高的时间分辨率较低,但其优势是获取海洋广大区域的TEC值。两种观测手段的研究区域互补,可以充分观测威德尔海异常在西南极的变化特征,从空间上来看,威德尔海异常出现在以别林斯高晋海为中心的广大区域,而威德尔海异常也是覆盖了西南极的别林斯高晋海、威德尔海以及可达80°S的西南极陆地区域。从时间上来看,出现时段在每年的10月底到次年3月初,夜晚电子密度增加,白天电子密度降低,随着太阳活动的增强,其异常程度也变大。 相似文献
10.
Over the past three decades, radar altimetry has made a significant contribution to marine gravity field modeling. To improve the accuracy and resolution, we propose a new twin-satellite altimetry. Such a system has several advantages. Among others, it provides (i) twice the number of samples per time epoch, and (ii) information about the cross-track surface gradient with high accuracy because most of the environmental and tidal errors will be common to the simultaneous measurements and therefore cancel out when computing the cross-track gradient computation. We describe a rigorous procedure for the deduction of the sea surface gradient at each altimeter observation point (i.e., not only at the crossovers), from the twin-satellite altimetry system. The precision of the gradient will be slightly affected by orbit errors, instrument drift, and inaccuracies in the geophysical corrections to be applied. We also demonstrate that a 1 mGal accuracy and 1 min resolution marine altimetry gravity field can be obtained if certain conditions are met. To achieve the expected goal, we recommend an orbital configuration, phasing two satellites in 4-s time delay such that the Earth rotation creates a natural baseline between the two satellites, and a 18 kHz SAR altimeter. 相似文献
11.
A technique is presented for the development of a high-precision and high-resolution mean sea surface model utilising radar
altimetric sea surface heights extracted from the geodetic phase of the European Space Agency (ESA) ERS-1 mission. The methodology
uses a cubic-spline fit of dual ERS-1 and TOPEX crossovers for the minimisation of radial orbit error. Fourier domain processing
techniques are used for spectral optimal interpolation of the mean sea surface in order to reduce residual errors within the
initial model. The EGM96 gravity field and sea surface topography models are used as reference fields as part of the determination
of spectral components required for the optimal interpolation algorithm. A comparison between the final model and 10 cycles
of TOPEX sea surface heights shows differences of between 12.3 and 13.8 cm root mean square (RMS). An un-optimally interpolated
surface comparison with TOPEX data gave differences of between 15.7 and 16.2 cm RMS. The methodology results in an approximately
10-cm improvement in accuracy. Further improvement will be attained with the inclusion of stacked altimetry from both current
and future missions.
Received: 22 December 1999 / Accepted: 6 November 2000 相似文献
12.
双星伴飞卫星测高模式及其轨道设计 总被引：1，自引：0，他引：1
为达到提高反演海洋重力场分辨率的要求,本文提出一种双星伴飞的测高卫星模式,并根据卫星轨道设计的基本要求,给出相应的卫星轨道设计方案。仿真分析表明,该方案可在卫星设计寿命内完成反演1′×1′空间分辨率海洋重力场的要求,且观测数据覆盖了全球大部分海洋区域。该模式可实现星下点海平面梯度的实时测量,提出了改进测高反演海洋重力场的精度的新思路。 相似文献
13.
Alessandro Caporali 《Journal of Geodesy》1993,67(3):139-147
Summary A local model of the geoid in NE Italy and its section along the Venice ground track of the ERS-1 satellite of the European Space Agency is presented. The observational data consist of geoid undulations determined with a network of 25 stations of known orthometric (by spirit leveling) and ellipsoidal (by GPS differential survey) and of 13 deflections of the vertical measured at sites of the network for which, besides the ellipsoidal (WGS84) coordinates, also astronomic coordinates were known. The network covers an area of 1×1 degrees and is tied to a vertical and horizontal datum: one vertex of the network is the tide gauge of Punta Salute, in Venice, providing a tie to a mean sea level; a second vertex is the site for mobile laser systems at Monte Venda, on the Euganei Hills, for which geocentric coordinates resulted from the analysis of several LAGEOS passes.The interpolation algorithm used to map sparse and heterogeneous data to a regular grid of geoid undulations is based on least squares collocation and the autocorrelation function of the geoid undulations is modeled by a third order Markov process on flat earth. The algorithm has been applied to the observed undulations and deflections of the vertical after subtraction of the corresponding predictions made on the basis of the OSU91A global geoid model of the Ohio State University, complete to degree and order 360. The locally improved geoid results by adding back, at the nodes of a regular grid, the predictions of the global field to the least squares interpolated values. Comparison of the model values with the raw data at the observing stations indicates that the mean discrepancy is virtually zero with a root mean square dispersion of 8 cm, assuming that the ellipsoidal heights and vertical deflections data are affected by a random error of 3 cm and 0.5 respectively. The corrections resulting from the local data and added to the background 360×360 global model are described by a smooth surface with excursions from the reference surface not larger than ±30 cm. 相似文献
14.
海面高度作为最重要的海洋物理参数之一,在预防海啸、风暴潮中起到重要作用,是海洋科学,遥感测绘领域的重要研究内容之一。粗糙度作为影响海面测高精度的重要因素之一,主要是由风速变化引起,本文为了探究风速引起的粗糙度变化对海面测高精度的影响,分别进行了湖面实验与海面实验。通过对风速与反射信号相位差RMS关系的研究,定性分析了粗糙度对测高精度的影响,结果表明,在反射信号相位差RMS增加0.005(单位rad)时,测高的误差RMS增加了近一倍。 相似文献
15.
Absolute seafloor vertical positioning using combined pressure gauge and kinematic GPS data 总被引：1，自引：0，他引：1
Valérie Ballu Marie-Noelle Bouin Stéphane Calmant Eric Folcher Jean-Michel Bore Jérome Ammann Olivier Pot Michel Diament Bernard Pelletier 《Journal of Geodesy》2010,84(1):65-77
Knowledge of the position and motion of points on the seafloor can be critically important in both fundamental research (for
example, global geodesy and plate tectonics) and for more practical applications such as seismic risk evaluation, off-shore
construction and pipeline monitoring. In the Vanuatu subduction zone, for example, measuring deformation underwater could
provide valuable information for modeling deformation and understanding the seismic cycle. We report a shallow water experiment
in Vanuatu to measure the relative and absolute depth of seafloor points. The experiment differs from previous efforts mainly
in that it uses the height of the sea surface determined by kinematic GPS, allowing us to locate the points in a global reference
frame. The ITRF2005 ellipsoidal height of a seafloor benchmark was determined with a 1-sigma uncertainty of 0.7–2.1 cm. The
estimated ellipsoidal height differs only by a few tenths of a centimeter between measurements made in 2004 and another set
made in 2006. These results are encouraging and open new perspectives for vertical underwater deformation monitoring in shallow
water areas. Sea-surface GPS measurements can also help to reduce the uncertainty in depth difference determination for relative
measurements. 相似文献
16.
理解全球海平面变化具有十分重要的意义,它间接反映了地球系统中气候性相关因素的变化。本文基于一组海平面指纹和比容经验正交函数,联合时变重力数据和卫星测高数据反演了2002年4月至2020年2月的全球海平面变化,将全球海平面变化分解成南极冰盖融化、格陵兰冰盖融化、陆地冰川融化、陆地水储量变化、冰川均衡调整和海水比容效应这6个分量的贡献。联合反演结果显示,全球平均比容海平面变化为1.08±0.05 mm/a,与相关文献的结果相吻合。研究发现,联合测高数据和时变重力数据的反演方法能够一定程度上减弱GRACE Follow-On卫星时期海水质量变化被低估的现象。本文利用联合反演的结果研究了区域海平面变化,在大部分近海区域反演效果较好,这表明该方法可用于区域海平面变化的研究。 相似文献
17.
A new gravity map, a new marine geoid around Japan and the detection of the Kuroshio current 总被引：3，自引：0，他引：3
About half a million marine gravity measurements over a 30∘×30∘ area centered on Japan have been processed and adjusted to produce a new free-air gravity map from a 5′×5′ grid. This map
seems to have a better resolution than those previously published as measured by its correlation with bathymetry. The grid
was used together with a high-degree and -order spherical harmonics geopotential model to compute a detailed geoid with two
methods: Stokes integral and collocation. Comparisons with other available geoidal surfaces derived either from gravity or
from satellite altimetry were made especially to test the ability of this new geoid at showing the sea surface topography
as mapped by the Topex/Poseidon satellite. Over 2 months (6 cycles) the dynamic topography at ascending passes in the region
(23∘47∘N and 123∘147∘E) was mapped to study the variability of the Kuroshio current.
Received: 15 July 1994 / Accepted: 17 February 1997 相似文献
18.
联合Argo浮标、卫星测高和GRACE数据研究海平面变化 总被引：1，自引：1，他引：0
卫星测高、GRACE、Argo等数据为监测海平面变化提供了丰富的观测数据,利用Argo数据计算的比容海平面变化,可以更加深入地理解卫星测高以及卫星重力获得的海平面变化。利用2004年1月至2010年12月间Argo浮标采集的温度和盐度数据,通过数值积分方法计算了65°S~65°N间的比容海平面异常,并通过最小二乘拟合得到比容海平面变化的长期趋势为0.63±0.45 mm/a,与Llovel得到的结果吻合较好。利用卫星测高数据得到该时间段内海平面变化趋势为2.52±0.71 mm/a,GRACE反演得到的海水质量变化引起的海平面趋势为1.84±0.13mm/a,结果表明海水质量变化成为引起海平面变化的主要因素。最后对联合卫星测高、GRACE得到比容海平面变化与相应Argo浮标数据计算结果的空间分布特征进行了比较。 相似文献
19.
全球卫星导航系统(GNSS)不仅具有导航定位、测速以及授时等功能,且因其反射信号能被接收,可用于海面风场、海面高度反演，由此开辟了一个新的研究领域GNSS反射(GNSS-R)技术，GNSS-R技术用于海洋遥感是一个新的研究领域；文中主要介绍了GNSS-R遥感技术和海面测高的研究进展,并从基于信噪比(SNR)数据测量法、基于 C／A码相位测量法、基于载波相位测量法及基于载波频率测量法等方面分析和总结了GNSS-R在海面高度测量的常用方法. 相似文献
20.
Regional scale urban built-up areas and surface urban heat islands (SUHI) are important for urban planning and policy formation. Owing to coarse spatial resolution (1000 m), it is difficult to use Moderate Resolution Imaging Spectroradiometer (MODIS) Land surface temperature (LST) products for mapping urban areas and visualization, and SUHI-related studies. To overcome this problem, the present study downscaled MODIS (1000 m resolution)-derived LST to 250 m resolution to map and visualize the urban areas and identify the basic components of SUHI over 12 districts of Punjab, India. The results are compared through visual interpretation and statistical procedure based on similarity analysis. The increased entropy value in the downscaled LST signifies higher information content. The temperature variation within the built-up and its environs is due to difference in land use and is depicted better in the downscaled LST. The SUHI intensity analysis of four cities (Ludhiana, Patiala, Moga and Vatinda) indicates that mean temperature in urban built-up core is higher (38.87 °C) as compared to suburban (35.85 °C) and rural (32.41 °C) areas. The downscaling techniques demonstrated in this paper enhance the usage of open-source wide swath MODIS LST for continuous monitoring of SUHI and urban area mapping, visualisation and analysis at regional scale. Such initiatives are useful for the scientific community and the decision-makers. 相似文献