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1.
NIEGuigen LIUJingnan 《地球空间信息科学学报》2005,8(1):8-13
Two methods for smoothing pseudorange observable by Carrier and Doppler are discussed. Then the procedure based on the RINEX observation files is tested using the Ashtech Z-XII3T geodetic receivers driven by a stable external frequency at UNSO. This paper proposes to adapt this procedure for the links between geodetic receivers, in order to take advantage of the P codes available on L1 and L2, This new procedure uses the 30-second RINEX observations files, the standard of the International GPS Service (IGS), and processes the ionosphere-free combination of the codes P1 and P2 ; the satellite positions are deduced from the IGS rapid orbits, available after two days. 相似文献
2.
The aim of this investigation is to study how to use a gravimetric(quasi) geoid for levelling by GPS data in an optimal way.The advent of precise geodetic GPS has made the use of a technique possible,which might be called GPS- gravimetric geoid determination.In this approach,GPS heights above the reference ellipsoid are determined for points whose levelled (orthometric) height H is above sea level people have already surveyed;for these points,we thus have the values of the geoid undulation N.These values are then used to constrain the geoid undulations N‘ obtained from the gravimetric solution. 相似文献
3.
GAOWei XUShaoquan YUXuexiang 《地球空间信息科学学报》2003,6(4):61-65
The feasibility of monitoring the change of city settlement using GPS surveying instead of leveling is studied. A fiducial network and a monitoring network are established in Ningbo city. Two periods of GPS observation are completed. Some measures are taken during the observation in order to ensure to obtain the high-precise height component. The Saastamoinen model is adopted in the data processing of the dry component part of the tropospheric delay. The wet component change of the tropospheric delay is estimated by stochastic processes model. When Bernese software is used to process the data, the millimeter level precision of height measuring is achieved. 相似文献
4.
Dynamic characteristics of large structures,such as tall buildings,long-span suspension,cable-stayed bridges and tall chimneys,are key to assess their drift and stress conditions.The dynamic characteristics of large structures are difficult to measure directly under the condition of earthquakes or strong winds using traditional techniques such as laser collimator,total station and accelerometers.Therefore there is a great need for developing new method or technique for this purpose.Recent advances in Global Positioning System (GPS) technology provide a great opportunity to monitor long-period changes of structures reliably.GPS receivers capable to gauge the motion at the centimeter or sub-centimeter level with sampling frequency 10Hz or even 20 Hz are now available from several manufacturers.To the authors' knowledge,the capability of identifying dynamic characteristics from GPS observations has not been widely verified.For the feasibility study on using kinematic GPS technology to identify the dynamic characteristics of tall buildings,some experiments were conducted in a simulative environment.This paper discusses in detail the experiment device,and the ways through them GPS data are recorded,processed and analyzed.With post-processing version of NovAtel's Softsurv software and auto-regressive (AR) spectral analysis method,relative displacements and corresponding vibrating frequencies have been derived from GPS observations.The results indicate that the dynamic characteristics can be identified accurately by kinematic GPS technology. 相似文献
5.
LI Guoping HUANG Dingfa LIU Biquan CHEN Jiaona 《地球空间信息科学学报》2007,10(3):181-185
The estimates of total zenith delay are derived using Bernese GPS Software V4. 2 based on GPS data every 30 s from the first measurement experiment of a ground-based GPS network in Chengdu Plain of Southwest China during the period from July to September 2004. Then the estimates of 0.5 hourly precipitable water vapor (PWV) derived from global positioning system (GPS) are obtained using meteorological data from automatic weather stations (AWS). The comparison of PWV derived from GPS and those from radiosonde observations is given for the Chengdu station, with RMS (root mean square) differences of 3.09m. The consis- tency of precipitable water vapor derived from GPS to those from radiosonde is good. It is concluded that Bevis’ empirical formula for estimating the weighted atmospheric mean temperature can be applicable in Chengdu area because the relationship of GPS PWV with Bevis’ formula and GPS PWV with radiosonde method shows a high correlation. The result of this GPS measurement experiment is helpful both for accumu- lating the study of precipitable water vapor derived from GPS in Chengdu areas located at the eastern side of the Tibetan Plateau and for studying spatial-temporal variations of regional atmospheric water vapor through many disciplines cooperatively. 相似文献
6.
The Above Ground Biomass(AGB) estimates of vegetation comprise both the bole biomass determined through a volumetric equation and litter biomass collected from the ground.For mature trees,the AGB estimated in phenologically different time periods is directly affected by the litter biomass since the Diameter at Breast Height(DBH) and height(H) of such trees that are used in the estimation of bole biomass would remain unchanged over a reasonable time period.In the present study,we have determined the AGB of Sal trees(Shorea robusta) in two contrasting seasons:the peak green period in October being devoid of lit-ter on the ground and the leaf shedding period in February with abundant amount of litter present on the ground.Estimation of AGB for the month of February included the litter biomass.In contrast,the AGB for October represented only the bole biomass.AGB was estimated for ten different plots selected in the study area.The AGB estimated from ten sampling plots for each time period was re-gressed with the individual tree parameters such as the average DBH and height of trees measured from the corresponding plots.The regression analysis exhibited a significantly stronger relationship between the AGB and DBH for the month of October as compared to February.Furthermore,the correlation between the remotely sensed derived data and AGB was also found to be significantly higher for the month of October than February.This observation indicates that inclusion of the litter biomass in AGB will tend to decrease the re-gression relationship between AGB and DBH and also between the remotely sensed data and AGB.Therefore,these conclusions invite careful consideration while estimating AGB from satellite data in phenologically different time periods. 相似文献
7.
The purpose for this article is to research the relationship between public transportation and real estate based on the area of East Lansing.Two methods are mainly used to analyze the data:correlation analysis and means analysis with the help of Statistical Package for the Social Sciences(SPSS) data analyzing software.There are two analysis results:(1) the real estate,which is closer to public transportation,will have higher value than that is far from public transportation,and(2) the number of bus in one bus stop has no obvious relation with the value of real estate.Based on these results,real estate developers could build residential real estate close to public transportation or bring public transportation in their real estate community by contract with transportation corporations.In sum,they should reasonably use public transportation as attractive features to convince people to prefer to their houses. 相似文献
8.
LIUChun SHIWenzhong LIUDajie 《地球空间信息科学学报》2003,6(2):13-19
On the basis of the principles of simple random sampling,the statistical model of rate of disfigure-ment(RD)is put forward and described in detail.According to the definition of simple random sampling for the attribute data in GIS,the mean and variance of the RD are deduced as the characteristic value of the statistical model in order to explain the feasibility of the accuracy measurement of the attribute data in GIS by using the RD.Moreover,on the basis of the mean and variance of the RD,the quality assessment method for attribute data of vector maps during the data collecting is discussed.The RD spread graph is also drawn to see whether the quality of the attribute data is under control.The RD model can synthetically judge the quality of attribute data,which is different from other measurement coefficients that only discuss accuracy of classification. 相似文献
9.
Evaluation of CHAMP satellite orbit with SLR measurements 总被引：1，自引：0，他引：1
QIN Xianping YANG Yuanxi 《地球空间信息科学学报》2005,8(3):209-213
The technique of Evaluating CHAMP satellite orbit with SLR measurements iS presented. As an independent evaluation of the orbit solution, SLR data observed from January 1 to 16, 2002 are processed to compute the residuals after fixing the GFZ＇s post science orbits solutions. The SLR residuals are computed as the differences of the SLR measurements minus the corresponding distances between the SLR station and the GPS-derived orbit positions. On the basis of the SLR residuals analysis, it is found that the accuracy of GFZ＇ s post science orbits is better than 10 cm and that there is no systematic error in GFZ＇s post science orbits. 相似文献
10.
LUO Jia NING Jinsheng LUO Zhicai 《地球空间信息科学学报》2005,8(3):205-208,219
Satellite-to-Satellite Tracking in low-low model （SST-Ⅱ） is a new technique to resolve the series of problems met in the determination of the earth＇s gravity field. As the key technique of SST-Ⅱ, KBR can get SST-Ⅱ measurements directly. So the KBR performance analysis is the first step in SST-Ⅱ design. In this paper, assuming that the satellite pairs of SST-Ⅱ are in near circle polar orbits, the spectrum relationship between the earth gravity field and KBR is established using analytic method. And then some examples are analyzed, the suggestions and conclusions are drawn from these examples. The research results could be taken as a reference for future satellite gravity project of China. 相似文献
11.
Orbit fitting is used in many GPS applications. For example, in Precise Point Positioning (PPP), GPS orbits (SP3 orbits) are normally retrieved either from IGS or from one of its Analysis Centers (ACs) with 15 minutes’ sampling, which is much bigger than the normal observation sampling. Therefore, algorithms should be derived to fit GPS orbits to the observation time. Many methods based on interpolation were developed. Using these methods the orbits fit well at the sampling points. However, these methods ignore the physical motion model of GPS satellites. Therefore, the trajectories may not fit the true orbits at the periods in between 2 sampling epochs. To solve this problem, we develop a dynamic approach, in which a model based on Helmert transformation is developed in GPS orbit fitting. In this orbit fitting approach, GPS orbits at sampling points are treated as pseudo-observations. Thereafter, Helmert transformation is built up between the pseudo-observations and dynamically integrated orbits at each epoch. A set of Helmert parameters together with corrections of GPS initial orbits are then modeled as unknown parameters. Results show that the final fit orbits have the same precision as the IGS final orbits. 相似文献
12.
Combining the orbits of the IGS Analysis Centers 总被引：1，自引：0，他引：1
Currently seven Analysis Centers of the International GPS Service for Geodynamics (IGS) are producing daily precise orbits and the corresponding Earth Orientation Parameters (EOP). These individual products are available at several IGS Data Centers (e.g. CDDIS, IGN, SIO, etc.). During 1993 no official IGS orbits were produced, but the routine orbit comparisons by IGS indicated that, after small orientation and scale alignments, the orbit consistency was approaching the 20 cm level (a coordinate RMS), and that some orbit combination should be possible and feasible. An IGS combined orbit could provide a precise and efficient extension of the IERS Terrestrial Reference Frame (ITRF). Another advantage of such a combined orbit would be reliability and precision.Two schemes of orbit combinations are considered here: (a) the first method consists of a weighted averaging process of the earth-fixed satellite positions as produced by the individual Centers; (b) the second method uses the individual IGS orbit files as pseudo-observations in an orbit determination process, where in addition to the initial conditions, different parameter sets may be estimated. Both orbit combination methods have been tested on the January 1993 orbit data sets (GPS weeks 680 and 681) with an impressive agreement at the 5 cm level (coordinate RMS). The quality of the combined orbits is checked by processing a set of continental baselines in two different regions of the globe using different processing softwares. Both types of combined orbits gave similar baseline repeatability of a few ppb in both regions which compared favorably to the best individual orbits in the region. 相似文献
13.
马丙浩;田林亚;张勇 《东北测绘》2013,(4):103-105
介绍了GPS/GLONASS组合定位模型,探讨了组合定位解算中的时间系统转化和坐标系统转化的问题,研究了利用Helmert分差分量估计进行验后定权的方法及其步骤,对IGS基准站nano某一天的观测数据进行组合定位解算与分析,认为在GPS/GLONASS组合定位解算中选择1∶0.210 6的权比,能够提高单点定位的精度。 相似文献
14.
The Center for Orbit Determination in Europe (CODE) has been involved in the processing of combined GPS/GLONASS data during the International GLONASS Experiment (IGEX). The resulting precise orbits were analyzed using the program SORBDT. Introducing one satellites positions as pseudo-observations, the program is capable of fitting orbital arcs through these positions using an orbit improvement procedure based on the numerical integration of the satellites orbit and its partial derivative with respect to the orbit parameters. For this study, the program was enhanced to estimate selected parameters of the Earths gravity field. The orbital periods of the GPS satellites are —in contrast to those of the GLONASS satellites – 2:1 commensurable (P
Sid:P
GPS) with the rotation period of the Earth. Therefore, resonance effects of the satellite motion with terms of the geopotential occur and they influence the estimation of these parameters. A sensitivity study of the GPS and GLONASS orbits with respect to the geopotential coefficients reveals that the correlations between different geopotential coefficients and the correlations of geopotential coefficients with other orbit parameters, in particular with solar radiation pressure parameters, are the crucial issues in this context. The estimation of the resonant geopotential terms is, in the case of GPS, hindered by correlations with the simultaneously estimated radiation pressure parameters. In the GLONASS case, arc lengths of several days allow the decorrelation of the two parameter types. The formal errors of the estimates based on the GLONASS orbits are a factor of 5 to 10 smaller for all resonant terms.
AcknowledgmentsThe authors would like to thank all the organizations involved in the IGS and the IGEX campaign, in particular those operating an IGS or IGEX observation site and providing the indispensable data for precise orbit determination. 相似文献
15.
研究了GPS历书拟合算法,针对常用算法拟合精度受初值影响较大,且迭代计算一般不能收敛于最小拟合误差的情况,提出了称为"二步法"的改进历书拟合算法。即首先进行短弧拟合,并将拟合结果作为长弧拟合的初值使用;取计算过程中的最小拟合误差对应值代替最终收敛值作为拟合结果。经多组GPS实际轨道拟合试验,结果表明"二步法"拟合精度一般能提高约50%。 相似文献
16.
The International GNSS Service (IGS) provides Ultra-rapid GPS & GLONASS orbits every 6 h. Each product is composed of 24 h of observed orbits with predicted orbits for the next 24 h. We have studied how the orbit prediction performance varies as a function of the arc length of the fitted observed orbits and the parameterization strategy used to estimate the empirical solar radiation pressure (SRP) effects. To focus on the dynamical aspects of the problem, nearly ideal conditions have been adopted by using IGS Rapid orbits and known earth rotation parameters (ERPs) as observations. Performance was gauged by comparison with Rapid orbits as truth by examining WRMS and median orbit differences over the first 6-h and the full 24-h prediction intervals, as well as the stability of the Helmert frame alignment parameters. Two versions of the extended SRP orbit model developed by the Centre for Orbit Determination in Europe (CODE) were tested. Adjusting all nine SRPs (offsets plus once-per-revolution sines and cosines in each satellite-centered frame direction) for each satellite shows smaller mean sub-daily, scale, and origin translation differences. On the other hand, eliminating the four once-per-revolution SRP parameters in the sun-ward and the solar panel axis directions yields orbit predictions that are much more rotationally stable. We found that observed arc lengths of 40–45 h produce the most stable and accurate predictions during 2010. A combined strategy of rotationally aligning the 9 SRP results to the 5 SRP frame should give optimal predictions with about 13 mm mean WRMS residuals over the first 6 h and 50 mm over 24 h. Actual Ultra-rapid performance will be degraded due to the unavoidable rotational errors from ERP predictions. 相似文献
17.
18.
GPS精密星历插值方法的比较研究 总被引：17，自引：4，他引：17
GPS高精度测量中通常需要对GPS精密星历进行轨道插值，本文分别采用拉格朗日插值、切比雪夫多项式拟合以及线性逐次Neville插值三种方法对GPS卫星轨道进行了插值，比较了三种方法的特性及插值结果，得出了一些有益结论。 相似文献
19.
Stavros A. Melachroinos Frank G. Lemoine Douglas S. Chinn Nikita P. Zelensky Joseph B. Nicholas Brian D. Beckley 《GPS Solutions》2014,18(4):497-507
We examine the impact of using seasonal and long-period time-variable gravity field (TVG) models on GPS orbit determination, through simulations from 1994 to 2012. The models of time-variable gravity that we test include the GRGS release RL02 GRACE-derived 10-day gravity field models up to degree and order 20 (grgs20x20), a 4 × 4 series of weekly coefficients using GGM03S as a base derived from SLR and DORIS tracking to 11 satellites (tvg4x4), and a harmonic fit to the above 4 × 4 SLR–DORIS time series (goco2s_fit2). These detailed models are compared to GPS orbit simulations using a reference model (stdtvg) based on the International Earth Rotation Service (IERS) and International GNSS Service (IGS) repro1 standards. We find that the new TVG modeling produces significant along, cross-track orbit differences as well as annual, semi-annual, draconitic and long-period effects in the Helmert translation parameters (Tx, Ty, Tz) of the GPS orbits with magnitudes of several mm. We show that the simplistic TVG modeling approach used by all of the IGS Analysis Centers, which is based on the models provided by the IERS standards, becomes progressively less adequate following 2006 when compared to the seasonal and long-period TVG models. 相似文献
20.
A New Solar Radiation Pressure Model for GPS Satellites 总被引：11，自引：3，他引：8
The largest error in currently used GPS orbit models is due to the effect of solar radiation pressure. Over the last few years
many improvements were made in modeling the orbits of GPS satellites within the International GPS Service (IGS). Howeer, most
improvements were achieved by increasing the number of estimated orbit and/or solar radiation pressure parameters. This increase
in the number of estimated satellite parameters weakens the solutions of all estimated parameters (not only orbit parameters).
Because of correlations the additional orbit parameters may introduce biases in other estimated quantities, for example the
length of day. We present a recently developed solar radiation pressure model for the GPS satellites. This model is based
on experiences and results gained at the Center for Orbit Determination in Europe (CODE) in the context of its IGS activities
since June 1992. The performance of the new model is almost an order of magnitude better than that of the existing ROCK models.
It also allows a reduction of the number of orbit parameters that have to be estimated. ? 1999 John Wiley & Sons, Inc. 相似文献