2003 Vol. 28, No. 4
The fundamentals of exterior orientation elements calculation by orientation images method and EFP(equivalent frame photo) method are reviewed briefly.And so far,none of aerial triangulation with three-line array CCD image and ground control points can pass through the similarity(no count of image observational error) between real model and the model estimated by single strip adjustment computed with the help of four control points at the corners of the strip is indicated.Based on the aerial triangulation by EFP method,the reason of the presented problem is studied deeply.The addition of connected point(s) between neighbor EFP is proposed,and meanwhile,the ground coordinates of connected points located in the first and last baselengths of the strip are given or either of connected point coordinates in the left or right EFP is true.With the alternative control,the adjustment results can almost make the model calculated by single strip adjustment similar with real model.And several final statistical results of adjustment using computer simulated data are listed.
An efficient signal fusion method is put forward for the integrated navigation of the multiple sensor system.To show the correlations of the master filter and the local filters,the covariance matrix among the local filter outputs and that of the local filter and master filter outputs are presented.In order to avoid the correlations between the fusion data sets of the multiple sensors,a synthetic Kalman filtering composed by a kinematic Kalman filtering step and several static Kalman filtering steps is presented.The new developed robust Kalman filtering and the adaptively robust Kalman filtering can be easily extended in this kind of synthetic filtering.
Three areas of technology are thought to be the newest technology for shallow water hydrographic surveys owing to their high speed and high resolution:airborne laser hydrography(ALH),shallow water multibeam sonars(SWMB) and digital side scan sonar.The wave correction is one of the most important depth reductions for marine environment.Based on the configuration of the first set of ALH system in China,three ways available for the wave correction are proposed,and their suitability is discussed in detail.Finally,the accuracy of the correction models is estimated in theory.
With the continuous GPS monitoring data of the eight points of the Three Gorge area,the Zenith Total Delay over each points are extracted out.When processing the GPS data,we make use of the observation data of three IGS stations to minimize the correlation between ZTDs.After separating the zenith hydrostatic delay with the extrapolated surface pressure and Saastanmonien model,we get the zenith wet delay(ZWD).The ZWD sequential lines of all points are consistent.After analyzing the ZWD distribution figures of 8 hours in this area,some information of variation of the water vapor can be obtained.The feasibility of monitoring water vapor distribution and variation with ground-based GPS meteorology is discussed.Some conclusions and suggestions are obtained.
The difference between the integrated water vapor(IWV) calculated from the Saastamoinen and Hopfield models in high elevation area is analysed.The analyses show that the IWV calculated from Saastamoinen model is good for the radiosonde data,and that Hopfield model tends to overpredict IWV in high elevation area.By analyzing and researching the real measurements in different elevation stations,the modified item of Hopfield model is given.The calculating result of Saastamoinen and Hopfield models are completely consistent.
Based on the development of data snooping method to find observation gross errors in geodetic network and the theory for simultaneous location and evaluation of multi-dimensional gross errors,an algorithm for searching,judging and determining multi-dimensional gross errors simultaneously is proposed.The results show that this algorithm is available through calculation and analysis of two examples.
Based on the theory of ocean loading tide,by using NAO99b global ocean tide model,the ocean tidal displacement corrections for some IGS stations in China are calculated.These corrections are also applied to GPS data processing.The GPS baseline components and station coordinates computed by the GAMIT software with and without these corrections are computed,compared and analyzed.The results show that the ocean tidal displacement corrections have effects both on GPS baseline components and on station coordinates.To short time GPS data processing,the corrections are more than 1mm;but to long time processing,the corrections have little effects.
This paper first introduces the code and phase models used in precise point positioning(PPP) method,then the principle and simple procedure of PPP processing algorithm are introduced,and the main error sources of PPP method are presented.A lot of attentions are paid to the methods of quality control for PPP method.What's more,the estimation and interpolation of satellite clock errors,the consistence of data and solution and the accuracy that PPP method can attain are discussed.Last,an example of PPP is processed and the corresponding results are compared with the results obtained by using GPS double difference observations.The results show that the accuracy of PPP can attain cm-precision and is approximately equal to that of double difference with long baselines(>1 000km).
The crustal movement observation network of China was set up in 1999.It has collected a long term GPS data set over three years which has made great contributions to crustal deformation study.We compute the GPS time series of all 25 permanent stations of CMONOC from March 1999 to March 2002 using GIPSY software of JPL.The average daily solutions of most GPS sites are over 850.The unfiltered GPS results are transferred to ITRF97 and then 10th-degree polynomialed for analysis.We can distinguish an annual period from the fitted curve of vertical time series.The crest and trough appearing at different season in different region indicates that the vertical accuracy of GPS measurements are mainly caused by atmosphere modeling error existing in the GPS computation.In order to study the crustal deformation,the GPS site must be established on stable bedrock.The repeated survey should be occupied at the same season and a long time series of GPS observations are necessary as well.
The network layout,site choice,observation project and data-processing method are introduced,and the method of result processing and analysis with five times observation is demonstrated by GPS technology,plate conformation and movement in Xinjiang area are studied.
This paper studies the ionospheric TEC calculated f rom the GPS data received in Wuhan,Beijing,Wulumuqi stations during the flare burst on July 14,2000.The TEC in the ionosphere is calculated.The method for calculating TEC enhancement only caused by the solar flare is presented.The calculating results indicate that the polynomial fitting method can effectively calculate TEC enhancement.The fitting period of time should be chosen by the actual TEC curve.
The GPS height time series are investigated by using the spectrum methods and wavelets methods.The maximum likelihood method is employed to separate the white noise and colored noise.The AR models for the GPS height time series are also achieved.Then the behaviors of colored noise in the time series are conduced.
In the parameter estimation,there exist two problems:changing the equivalences of the equations makes estimation results biased;determining the ridge parameter k is very difficult and random.To solve the two problems,this paper presents the iteration method by correcting characteristic value.The co-factor matrix QXX is derived firstly,then proves that QXX is just the Kaley inverse N-1 of N in the case of rank-full,which is Moore-Penrose inverse N+ of N in the case of rank-defect.
Two methods are presented in this paper,concerning that the gravity anomaly gradient and the gravity of the Earth's internal and its surface can be deduced and processed.The estimation of the orthometric height accuracy and its test and evaluation with models are discussed.
In order to advance the convergence effect,a set of asymptotic equations of the atmospheric gravitational load Love Numbers are presented.Green's functions of atmospheric gravitation loading,describing the Earth deformation which includes horizontal and vertical displacements,horizontal and vertical accelerations and strain tensor,are derived out by evaluating the properly weighted sums of the load Love numbers.By taking into account of asymptotic expressions of the gravitation load Love numbers,the Green's functions are reformulated to make them converge faster.This may improve the accuracy of the Green's functions in piratical computation.The numerical results of Green's functions for the unit point mass at the heights of 0km,1km,20km,6km above the Earth's surface are listed in Table 3.
The orbits of the GLONASS Satellites are determined by using the SLR data observed from March 28 to April 24,1999.The seven-day orbital arcs for the GLONASS satellites are computed.The results with the orbits of satellites computed by CODE are compared.The systematic error between SLR orbits and radiometric orbits of GLONASS satellites is confirmed.
This paper first analyses previous methods for solving the problem of computing the exterior orientation elements of satellite linear array scanner imagery.Then,the generalized ridge estimate is presented.The method of educing the parameters of generalized ridge estimate is explained in the end.Experiments prove that this method is very simple,steady and effective.
On the basis of the relative positioning method and the revolving method,by using the precise leveling,a new method is put forward for examining the antenna phase center three-dimensional bias of GPS receiver with the geometric relation of the antenna phase centers and the mini baseline.The examples and results show that the antenna phase center bias of the same type of GPS receivers is close to the homology,and the difference in vertical heft is up to millimeters.Those of the different type receiver antennas have much more differences.
Since the least squares estimates(LS) is not sensitive to gross errors,the estimation will be incorrect,especially there are several gross errors in the observed value.Being dead against this problem,a method of robust estimation that connects linear programming with least squares estimation is given.The residuals using Linear Programming were used as initial value to iterate calculation.Test results have shown that this method has the abilities to detect and restrain multi gross error.
On the basis of the satellite perturbation theory and vector operation principle,the acceleration characteristics and its expression are presented.As to CHAMP's satellite orbit parameters,the magnitude orders of every perturbation item are computed.The results show that the acceleration correction magnitudes produced by the perturbations of the right ascension of the ascending node and the argument of perigee and by the indirect perturbations of the satellite motion and the coordination rotation are below 10-11 m·s-2 which can be neglected.
This paper proposes an applicable multi-scale GIS scheme and realize it with an appropriate spatial data model.The advantages and disadvantages of four typical multi-scale GIS schemes are analyzed.Based on the analysis,a new scheme-layered,leveled and partitioned scheme is proposed.In the scheme,the object district is divided in several scale layers.Then the minimum scale layer is divided into several smaller scale levels.The nearby larger scale layer is partitioned into several sub districts.Similarly,each sub district is divided into smaller levels,and nearby larger layer is partitioned into sub districts,and so on.Each district with its levels is stored in one database.Based on the spatial data model designed by the authors,according to map generalization methods,a multi-scale GIS data model which is suitable for the new scheme is successfully developed.For the purpose of verifying the validity and feasibility of the new scheme and model,a prototype of multi-scale GIS software is written.Experiments prove that the new scheme and model are really valid and feasible.
Mining subsidence is a kind of important environmental damage.How to monitor,manage and deal with mining subsiding land is one of the key issues of sustainable development of mining areas.GIS is an important tool in this field and will play an important role.GIS can be used from four levels.It can be concluded that GIS can play important roles in mining subsidence,and the combination of GIS with professional model can be used effectively.
In the light of the viewpoint of information processing,the establishment of a formal description model of directional relationships based on Voronoi diagram and Delaunay triangulation is presented.The logical structure and data structure of the model and the process of direction calculation are described in detail.To demonstrate the soundness of the model,some examples are given,and the advantages are discussed in the end.
The necessity and feasibility of the realization of CRM in the spatial way by using the spatial analysis of GIS and urban population and social-economic data are explored.A concept of customer spatial relationship management(CSRM) is proposed.Further more,the basic technical framework and characters of CSRM and its major functions in enterprise management and decision support are discussed.A new thought is explored in applying GIS to business analysis.
A new method of FCM considering the distribution of spatial data is put forward.In the new method,the weight factor related to the characteristics of the distribution of spatial data is taken into account.Thus,the result of classification by the new method is improved.Last,two tests are given to show the advantages and effectiveness of the new method.
This paper comprehensively analyses the typical characteristic of multi-resolution terrain models,uses a hidden quadtree and resolution choosing formula to set up data models,realizes a real-time interactive multi-resolution terrain model depending on eyes.Finally,the experiments are done and some useful results are given.
According to the field spectrum data collecting within Beijing area,some technical methods in data acquirement are discussed,which include environment condition,analysis of the character of desertificated land,strategy of sampling and selecting of instrument.Spectrum data collected by the ASDFR field spectroradiometer has been used as an example to show how the errors in data collecting can be eliminated.Ancillary data that effect spectrum data sharing are also discussed.
On the basis of the analysis of the propagation characteristics of spatial relation confliction in map objects displacement,an algorithm for the maintenance of the map objects' spatial relation in their displacement is presented.The algorithm is an integration of the spatial reasoning method and the finite element method.And some kernel problems of the algorithm of map objects' displacement are studied particularly.
With the development of GIS application ceaselessly,a mass of multi-scale geo-spatial data need to be analyzed and represented.The fundamentals of lifting scheme and the three constructing steps,are presented.As an example,the lifting scheme and the binary wavelet transform are applied to compress a certain DEM.Comparing with these two methods,it is easy to conclude that the lifting scheme has more than two superiorities.The experimental results show that the lifting scheme has excellent performance in DEM data multi-scale representation.
The background and content of the research on web server cluster system are introduced.The structure and all kind of key techniques to implement web server cluster system are described.The idea of most grading saturation and the algorithm of load balancing are presented.The way to constitute high efficiency scalability and availability web server cluster system is explained.