共查询到20条相似文献，搜索用时 968 毫秒
1.
This paper focuses on studying long distance transference of height datum across seas by combining ellipsoidal height derived from GPS with gravimetric geoid height.The Yellow Sea Height Datum is transferred to Yangshan Island which is 30 km away from Luchaogang in Shanghai.The stations heights derived in this way are compared with those determined from two independent sets of the tidal observations taken in two years,and the difference values are 1.0 cm and 6.0 cm,respectively.Moreover,the derived height differences between two sections on the island are also compared with the values derived from precise leveling with respect to the same section.The result shows that the inconsistencies are only 0.2 cm and 0.7 cm,respectively. 相似文献
2.
LI Jiancheng JIANG Weiping professor School of Geodesy Geomatics Wuhan University Luoyu Road Wuhan China. 《地球空间信息科学学报》2002,5(3):1-5
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3.
长距离跨海高程基准传递方法的研究 总被引：15，自引：0，他引：15
研究了利用GPS定位技术所确定的相对大地高差,联合精确的大地水准面差距进行高程传递的方法。在洋山岛地区,利用该方法将黄海高程由陆地传递到距离上海芦潮港300km的洋山岛上。传递后的高程与两种独立的潮位观测结果比较差值分别为1cm和6cm,传递后的两段高程差与洋山岛三等水准测量结果的独立高差比较为0．2cm和0．7cm。 相似文献
4.
This study scrutinises the use of terrestrial laser scanning (TLS) to measure diameter at breast height (DBH) and tree height at individual tree species level. LiDAR point cloud scans are collected from uniformly defined control points. The result of processed TLS data demonstrates the precise measurements of tree height and DBH by comparing it with field data (DBH, tree height, tree species and location). The average tree height and DBH obtained through TLS measurements were 9.44?m and 43.30?cm, respectively. A linear equation between TLS derived parameters and field measured values were established, which gave the coefficient of determination (r2) of 0.79 and 0.96 for tree height and DBH, respectively. Further, these parameters were used to calculate above ground biomass (AGB) for individual tree species by considering a non-destructive approach. The total AGB and carbon stock from 80 different trees are computed to be 49.601 and 22.320?tonnes, respectively. 相似文献
5.
A new gravimetric geoid model, USGG2009 (see Abbreviations), has been developed for the United States and its territories
including the Conterminous US (CONUS), Alaska, Hawaii, Guam, the Commonwealth of the Northern Mariana Islands, American Samoa,
Puerto Rico and the US Virgin Islands. USGG2009 is based on a 1′ × 1′ gravity grid derived from the NGS surface gravity data
and the DNSC08 altimetry-derived anomalies, the SRTM-DTED1 3′′ DEM for its topographic reductions, and the global geopotential
model EGM08 as a reference model. USGG2009 geoid heights are compared with control values determined at 18,398 Bench Marks
over CONUS, where both the ellipsoidal height above NAD 83 and the Helmert orthometric height above NAVD 88 are known. Correcting
for the ellipsoidal datum difference, this permits a comparison of the geoid heights to independent data. The standard deviation
of the differences is 6.3 cm in contrast to 8.4 cm for its immediate predecessor— USGG2003. To minimize the effect of long-wavelength
errors that are known to exist in NAVD88, these comparisons were made on a state-by-state basis. The standard deviations of
the differences range from 3–5 cm in eastern states to about 6–9 cm in the more mountainous western states. If the GPS/Bench
Marks-derived geoid heights are corrected by removing a GRACE-derived estimate of the long-wavelength NAVD88 errors before
the comparison, the standard deviation of their differences from USGG2009 drops to 4.3 cm nationally and 2–4 cm in eastern
states and 4–8 in states with a maximum error of 26.4 cm in California and minimum of −32.1 cm in Washington. USGG2009 is
also compared with geoid heights derived from 40 tide-gauges and a physical dynamic ocean topography model in the Gulf of
Mexico; the mean of the differences is 3.3 cm and their standard deviation is 5.0 cm. When USGG2009-derived deflections of
the vertical are compared with 3,415 observed surface astro-geodetic deflections, the standard deviation of the differences
in the N–S and E–W components are 0.87′′ and 0.94′′, respectively. 相似文献
6.
不同的GNSS采用的坐标系定义几乎相近,但参考椭球及其坐标实现不同,这将影响多GNSS融合导航定位效果。根据各GNSS坐标系所采用参考椭球的基本常数,计算比较了不同坐标系参考椭球参数的差异;导出了相应的正常重力公式,比较了这些正常重力公式确定的正常重力值差异;最后分别从坐标系统的定义与实现两个方面分析了其对定位结果的影响。结果表明:1)GPS(BDS)与Galileo和GLONASS所使用的参考椭球引起正常重力差约为0.15和0.30 mgal;2)GPS与BDS,Galileo及GLONASS所使用参考椭球引起纬度分量最大差异约为0.1 mm,3 cm和3 cm,高程分量约为0.1 mm,0.5 m和1 m;3)各GNSS所使用坐标框架间转换参数引起的坐标变化达到厘米级。 相似文献
7.
This paper provides numerical examples for the prediction of height anomalies by the solution of Molodensky's boundary value problem. Computations are done within two areas in the Canadian Rockies. The data used are on a grid with various grid spacings from 100 m to 5 arc-minutes. Numerical results indicate that the Bouguer or the topographicisostatic gravity anomalies should be used in gravity interpolation. It is feasible to predict height anomalies in mountainous areas with an accuracy of 10 cm (1) if sufficiently dense data grids are used. After removing the systematic bias, the differences between the geoid undulations converted from height anomalies and those derived from GPS/levelling on 50 benchmarks is 12 cm (1) when the grid spacing is 1km, and 50 cm (1) when the grid spacing is 5. It is not necessary, in most cases, to require a grid spacing finer than 1 km, because the height anomaly changes only by 3 cm (1) when the grid spacing is increased from 100 m to 1000 m. Numerical results also indicate that, only the first two terms of the Molodensky series have to be evaluated in all but the extreme cases, since the contributions of the higher order terms are negligible compared to the objective accuracy. 相似文献
8.
Richard H. Rapp 《Journal of Geodesy》1994,69(1):26-31
This paper discusses the separation between the reference surface of several vertical datums and the geoid. The data used includes a set of Doppler positioned stations, transformation parameters to convert the Doppler positions to ITRF90, and a potential coefficient model composed of the JGM-2 (NASA model) from degree 2 to 70 plus the OSU91A model from degree 71 to 360. The basic method of analysis is the comparison of a geometric geoid undulation derived from an ellipsoidal height and an orthometric height with the undulation computed from the potential coefficient model The mean difference can imply a bias of the datum reference surface with respect to the geoid. Vertical datums in the following countries were considered: England, Germany, United States, and Australia. The following numbers represent the bias values of each datum after adopting an equatorial radius of 6378136.3m: England (-87 cm), Germany (4 cm), United States (NGVD29 (-26 cm)), NAVD88 (-72 cm), Australia AHD (mainland, -68 cm); AHD (Tasmania, -98 cm). A negative sign indicates the datum reference surface is below the geoid. The 91 cm difference between the datums in England and Germany has been independently estimated as 80 cm. The 30 cm difference between AHD (mainland) and AHD (Tasmania) has been independently estimated as 40 cm. These bias values have been estimated from data where the geometric/ gravimetric geoid undulation difference standard deviation, at one station, is typically ±100 cm, although the mean difference is determined more accurately.The results of this paper can be improved and expanded with more accurate geocentric station positions, more accurate and consistent heights with respect to the local vertical datum, and a more accurate gravity field for the Earth. The ideas developed here provide insight on the determination of a world height system. 相似文献
9.
Cuixian Lu Xingxing Li Florian Zus Robert Heinkelmann Galina Dick Maorong Ge Jens Wickert Harald Schuh 《Journal of Geodesy》2017,91(9):1019-1029
Precise positioning with the current Chinese BeiDou Navigation Satellite System is proven to be of comparable accuracy to the Global Positioning System, which is at centimeter level for the horizontal components and sub-decimeter level for the vertical component. But the BeiDou precise point positioning (PPP) shows its limitation in requiring a relatively long convergence time. In this study, we develop a numerical weather model (NWM) augmented PPP processing algorithm to improve BeiDou precise positioning. Tropospheric delay parameters, i.e., zenith delays, mapping functions, and horizontal delay gradients, derived from short-range forecasts from the Global Forecast System of the National Centers for Environmental Prediction (NCEP) are applied into BeiDou real-time PPP. Observational data from stations that are capable of tracking the BeiDou constellation from the International GNSS Service (IGS) Multi-GNSS Experiments network are processed, with the introduced NWM-augmented PPP and the standard PPP processing. The accuracy of tropospheric delays derived from NCEP is assessed against with the IGS final tropospheric delay products. The positioning results show that an improvement in convergence time up to 60.0 and 66.7% for the east and vertical components, respectively, can be achieved with the NWM-augmented PPP solution compared to the standard PPP solutions, while only slight improvement in the solution convergence can be found for the north component. A positioning accuracy of 5.7 and 5.9 cm for the east component is achieved with the standard PPP that estimates gradients and the one that estimates no gradients, respectively, in comparison to 3.5 cm of the NWM-augmented PPP, showing an improvement of 38.6 and 40.1%. Compared to the accuracy of 3.7 and 4.1 cm for the north component derived from the two standard PPP solutions, the one of the NWM-augmented PPP solution is improved to 2.0 cm, by about 45.9 and 51.2%. The positioning accuracy for the up component improves from 11.4 and 13.2 cm with the two standard PPP solutions to 8.0 cm with the NWM-augmented PPP solution, an improvement of 29.8 and 39.4%, respectively. 相似文献
10.
综合利用中国海岸带GNSS水准和多源重力测量数据,通过精化陆海统一的重力似大地水准面计算高程异常零阶项,精密确定了中国1985国家高程基准相对于重力大地水准面的偏差。结果显示:中国1985国家高程基准相对于国际地球自转服务（International Earth Rotation Service,IERS）的IERS2010标准W0对应的重力大地水准面的偏差为30.4±1.0 cm;中国1985国家高程基准于20世纪80年代经琼州海峡传递到海南岛后,在1 cm精度水平上未发现明显差异;计算的重力似大地水准面经全球导航卫星系统（globa navigation satellite system,GNSS）水准外部检核,标准差约为4 cm,12个省市和陆海交界处在厘米级精度水平上无缝衔接。在近10 a内,天津市除西北角外,大部分地区存在地面下沉,东南部地面下沉约7 cm,上海市地面下沉约7 cm,浙江省、江苏省和福建省等沿海省份局部地区也出现地面下沉。 相似文献
11.
12.
Weixing Zhang Yidong Lou Shengfeng Gu Chuang Shi Jennifer S. Haase Jingnan Liu 《GPS Solutions》2016,20(4):665-676
We present the joint estimation model for Global Positioning System/BeiDou Navigation Satellite System (GPS/BDS) real-time clocks and present the initial satellite clock solutions determined from 106 stations of the international GNSS service multi-GNSS experiment and the BeiDou experimental tracking stations networks for 1 month in December, 2012. The model is shown to be efficient enough to have no practical computational limit for producing 1-Hz clock updates for real-time applications. The estimated clocks were assessed through the comparison with final clock products and the analysis of post-fit residuals. Using the estimated clocks and corresponding orbit products (GPS ultra-rapid-predicted and BDS final orbits), the root-mean-square (RMS) values of coordinate differences from ground truth values are around 1 and 2–3 cm for GPS-only and BDS-only daily mean static precise point positioning (PPP) solutions, respectively. Accuracy of GPS/BDS combined static PPP solutions falls in between that of GPS-only and BDS-only PPP results, with RMS values approximately 1–2 cm in all three components. For static sites, processed in the kinematic PPP mode, the daily RMS values are normally within 4 and 6 cm after convergence for GPS-only and BDS-only results, respectively. In contrast, the combined GPS/BDS kinematic PPP solutions show higher accuracy and shorter convergence time. Additionally, the BDS-only kinematic PPP solutions using clock products derived from the proposed joint estimation model were superior compared to those computed using the single-system estimation model. 相似文献
13.
从最小二乘配置方法的基本原理出发,以我国某地区范围内1km分辨率的大地水准面高模型数据为例,根据实用公式计算了试验区大地水准面高的协方差值后,采用多项式函数模型和高斯函数模型分别拟合了该地区大地水准面高的局部协方差函数,并对试验区内18个检核点做了推估计算。根据推估值(Nfit)与实测值(NGPSL)的比较分析表明,虽然多项式协方差函数模型略优于高斯协方差函数模型,但它们都能以厘米级的精度拟合局部大地水准面,这表明了配置法用于精化厘米级大地水准面的有效性。 相似文献
14.
Numerical simulation of troposphere-induced errors in GPS-derived geodetic time series over Japan 总被引：2，自引：2，他引：0
Troposphere-induced errors in GPS-derived geodetic time series, namely, height and zenith total delays (ZTDs), over Japan
are quantitatively evaluated through the analyses of simulated GPS data using realistic cumulative tropospheric delays and
observed GPS data. The numerical simulations show that the use of a priori zenith hydrostatic delays (ZHDs) derived from the
European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather model data and gridded Vienna mapping function
1 (gridded VMF1) results in smaller spurious annual height errors and height repeatabilities (0.45 and 2.55 mm on average,
respectively) as compared to those derived from the global pressure and temperature (GPT) model and global mapping function
(GMF) (1.08 and 3.22 mm on average, respectively). On the other hand, the use of a priori ZHDs derived from the GPT and GMF
would be sufficient for applications involving ZTDs, given the current discrepancies between GPS-derived ZTDs and those derived
from numerical weather models. The numerical simulations reveal that the use of mapping functions constructed with fine-scale
numerical weather models will potentially improve height repeatabilities as compared to the gridded VMF1 (2.09 mm against
2.55 mm on average). However, they do not presently outperform the gridded VMF1 with the observed GPS data (6.52 mm against
6.50 mm on average). Finally, the commonly observed colored components in GPS-derived height time series are not primarily
the result of troposphere-induced errors, since they become white in numerical simulations with the proper choice of a priori
ZHDs and mapping functions. 相似文献
15.
Forest structural diversity metrics describing diversity in tree size and crown shape within forest stands can be used as indicators of biodiversity. These diversity metrics can be generated using airborne laser scanning (LiDAR) data to provide a rapid and cost effective alternative to ground-based inspection. Measures of tree height derived from LiDAR can be significantly affected by the canopy conditions at the time of data collection, in particular whether the canopy is under leaf-on or leaf-off conditions, but there have been no studies of the effects on structural diversity metrics. The aim of this research is to assess whether leaf-on/leaf-off changes in canopy conditions during LiDAR data collection affect the accuracy of calculated forest structural diversity metrics. We undertook a quantitative analysis of LiDAR ground detection and return height, and return height diversity from two airborne laser scanning surveys collected under leaf-on and leaf-off conditions to assess initial dataset differences. LiDAR data were then regressed against field-derived tree size diversity measurements using diversity metrics from each LiDAR dataset in isolation and, where appropriate, a mixture of the two. Models utilising leaf-off LiDAR diversity variables described DBH diversity, crown length diversity and crown width diversity more successfully than leaf-on (leaf-on models resulted in R² values of 0.66, 0.38 and 0.16, respectively, and leaf-off models 0.67, 0.37 and 0.23, respectively). When LiDAR datasets were combined into one model to describe tree height diversity and DBH diversity the models described 75% and 69% of the variance (R² of 0.75 for tree height diversity and 0.69 for DBH diversity). The results suggest that tree height diversity models derived from airborne LiDAR, collected (and where appropriate combined) under any seasonal conditions, can be used to differentiate between simple single and diverse multiple storey forest structure with confidence. 相似文献
16.
Regional height systems do not refer to a common equipotential surface, such as the geoid. They are usually referred to the mean sea level at a reference tide gauge. As mean sea level varies (by ±1 to 2 m) from place to place and from continent to continent each tide gauge has an unknown bias with respect to a common reference surface, whose determination is what the height datum problem is concerned with. This paper deals with this problem, in connection to the availability of satellite gravity missions data. Since biased heights enter into the computation of terrestrial gravity anomalies, which in turn are used for geoid determination, the biases enter as secondary or indirect effect also in such a geoid model. In contrast to terrestrial gravity anomalies, gravity and geoid models derived from satellite gravity missions, and in particular GRACE and GOCE, do not suffer from those inconsistencies. Those models can be regarded as unbiased. After a review of the mathematical formulation of the problem, the paper examines two alternative approaches to its solution. The first one compares the gravity potential coefficients in the range of degrees from 100 to 200 of an unbiased gravity field from GOCE with those of the combined model EGM2008, that in this range is affected by the height biases. This first proposal yields a solution too inaccurate to be useful. The second approach compares height anomalies derived from GNSS ellipsoidal heights and biased normal heights, with anomalies derived from an anomalous potential which combines a satellite-only model up to degree 200 and a high-resolution global model above 200. The point is to show that in this last combination the indirect effects of the height biases are negligible. To this aim, an error budget analysis is performed. The biases of the high frequency part are proved to be irrelevant, so that an accuracy of 5 cm per individual GNSS station is found. This seems to be a promising practical method to solve the problem. 相似文献
17.
不同插值方法对CORS高程时间序列的影响分析 总被引：2，自引：0，他引：2
在CORS站高程时间序列的研究中,当连续缺失较多数据时,插值显得尤为重要。为了较好地解决这个问题,本文尝试采用正交多项式拟合的方法,分别利用正交多项式拟合、拉格朗日和三次样条等插值方法对高程时间序列进行插值,并对不同方法的插值结果进行了分析比较,验证了正交多项式拟合的可行性及有效性。结果表明:在高程时间序列插值中,三次样条插值结果较差;连续缺失3个点及以下时,正交多项式拟合、拉格朗日插值结果均较好,插值效果相当;随着缺失点数量的增加,正交多项式拟合结果要优于另2种方法。 相似文献
18.
详细阐述了利用GLAS数据和GPS数据生成Dome-A地区DEM的方法。首先进行GLAS数据转化, 便于与GPS数据结合, 提出一种快速搜索GLAS和其光斑(Footprint)覆盖GPS点的算法, 比较GLAS数据和GPS数据发现, 均值差异最大为1.118 m, 最小为0.997 m, 而标准差稳定为5-6 cm, 在进行椭球变换修正之后, 差值最大为0.405 m, 最小为0.284 m;之后利用改进的角度限差法沿测线对GPS数据进行特征点提取, 得到抽稀之后的数据;再利用抽稀之后的GPS数据和处理后的GLAS数据使用克里金插值方法生成研究区DEM。利用1199个GPS点和53个GLAS检验点对最后生成的DEM进行了精度分析, 残差中误差为5 cm, 最大残差绝对值为12 cm。利用原始GPS数据, 原始GPS数据和GLAS数据, 处理后GPS数据利用克立金插值方法分别生成了研究区的DEM, 通过等高线提取分析以及检验点的误差分析, 处理后的GPS数据生成的DEM要优于原始GPS数据的, 证明GPS处理的必要性。 相似文献
19.
Estimation of dynamic ocean topography in the Gulf Stream area using the Hotine formula and altimetry data 总被引：3，自引：2，他引：1
Changyou Zhang 《Journal of Geodesy》1998,72(9):499-510
Two modifications of the Hotine formula using the truncation theory and marine gravity disturbances with altimetry data are
developed and used to compute a marine gravimetric geoid in the Gulf Stream area. The purpose of the geoid computation from
marine gravity information is to derive the absolute dynamic ocean topography based on the best estimate of the mean surface
height from recent altimetry missions such as Geosat, ERS-1, and Topex. This paper also tries to overcome difficulties of
using Fast Fourier Transformation (FFT) techniques to the geoid computation when the Hotine kernel is modified according to
the truncation theory. The derived absolute dynamic ocean topography is compared with that from global circulation models
such as POCM4B and POP96. The RMS difference between altimetry-derived and global circulation model dynamic ocean topography
is at the level of 25cm. The corresponding mean difference for POCM4B and POP96 is only a few centimeters. This study also
shows that the POP96 model is in slightly better agreement with the results derived from the Hotine formula and altimetry
data than POCM4B in the Gulf Stream area. In addition, Hotine formula with modification (II) gives the better agreement with
the results from the two global circulation models than the other techniques discussed in this paper.
Received: 10 October 1996 / Accepted: 16 January 1998 相似文献
20.
Christopher Jekeli 《Journal of Geodesy》1983,57(1-4):10-28
The problem of the divergence of the geopotential spherical harmonic series at the earth's surface is investigated from a numerical, rather than a theoretical, approach. A representative model of the earth's potential is devised on the basis of a density layer, which, in the spherical approximation, generates a gravity field whose harmonic constituents decay according to an accepted degree variance model. This field, expanded to degree 300, and a topographic surface specified to a corresponding resolution of 67 km are used to compute the differences between truncated inner and outer series of the gravity and height anomalies at the surface of the earth model. Up to degree 300, these differences attain RMS values from 0.33 μgal to 86 μgal for the gravity anomaly and from 0.32 μm to 410 μm for the height anomaly, in areas ranging respectively from near the equator to the vicinity of the pole. In addition to these values, there is an expected truncation effect, caused by the neglect of higher degree components of the inner series, of about 30 mgal and 36 cm, respectively. The field is then subjected to a Gaussian filter which effectively cuts off information at degree 300 (at the 5% level). The RMS error to degree 300 is thereby reduced by factors of 10 to 20, with a concomitant reduction in the truncation effect to about 0.3 mgal and 0.7 cm. 相似文献