2002 Vol. 27, No. 2
In this paper the error sources related to the laser instrument,GPS,and INS are analyzed in details.Several coordinate systems used in airborne laser scanning are set up,and then thebasic formula of the system is given.This paper emphasizes on discussing the kinematic offset correction between GPS antenna phase center and laser pulse fired point.And kinematic time delay influence on laser footprint position,the ranging errors,positioning errors,attitude errors and inte-gration errors of the system are also explored.Finally,the result shows that the kinmatic time delay can be neglected in comparison with other errors.The accuracy of the coordinates is not only influenced by the amplitude of the error,but also controlled by the flight height,scanning angle amplitude and attitude magnitude.
In this paper the ICW and the FICN are studied retaining the super rotation rate of the inner core relative to the mantle and the obliquity of the inner core axis relative to the mantle axis for a simple earth model of which both the mantle and the inner core are axially symmetrical and rigid.Although the adoption of such a simple earth model does not permit to obtain more accurate results,this permits to treat the problem entirely analytically,and thus to have more insight to the nature of the problem.
The authors inverted density anomalies on the different layer in the depth range of 10~100 km in Sanjiang Region,using gravity field that is treated by separation and adjustment.The results of combining other geophysical data to analyse the density data show that:1) The material in Sanjiang Region possibly comes from the extension of the Qinghai-Tibet Plateau;2) Low velocity layer exits in the crust of Sanjian Region;3) The earthquake easily occurred at the inflection points of density and gravity anomalies in lithosphere,especially at the complex inflection.
This paper proposes a method,topologically constrained recognition method(TCRM) which can simultaneously recognize the blocks and their deformation parameters of a landslide by using only the surface displacements.In TCRM,the blocks are recognized according to whether the displacements on the blocks fit their deformation model properly.The judgment is a recursive process.The recognizing process is constrained by a topological matrix.As a statistical model recognition method,its idea may be used to recognize the blocks of any other objects only if each block has continuous linear characteristics.The recognizing process is accomplished automatically.In this paper,TCRM is first used to deal with landslide deformation model recognition.Some problems in practical use,such as the block concept,3D model and recognition approach,are discussed in detail.A famous landslide,called Baota Landslide,which lies in the Three Gorges Reservoir bank,is analyzed.The surface deformation of the Baota Landslide has been observed since 1997 using GPS receiver.We use the series observation data of six epochs to recognize the sliding block structure of every observation term.
At present,there exist two types of method used to recover the bathymetry from altimeter data,i.e.the deterministic methods and the statistical method.In this paper,the principles of the two method are introduced first.Then on the basis of the theory of least-square collocation,a modified statistical model for recovering bathymetry from altimeter data is proposed.The new model is used to compute the ocean depth in the South China Sea from altimeter-derived gravity anomalies.And finally the predicted depths are compared to the ship-borne depth.
Airborne laser depth sounding(lidar bathymetry) is thought to be one of the most promising techniques for rapid and high density sounding of shallow waters.As we know,there exist two types of scanning mode for airborne laser bathymetric system(ALBS).When running the first mode,the system gains good computation efficiency but loses its stability.Contrarily,when running the second mode,the system gains its stability but loses computation efficiency.Nowadays most of ALBSs have changed their line-scanning mode to the new ellipse-scanning mode due to the great advancement in the computer technology.On the basis of the ellipse-scanning mechanism,this paper deduces a series of mathematical models for ALBS's data-processing and evaluates the models'accuracy by analog-computation.Finally this paper analyzes the characteristics of the ALBS's sea-surface scanning track.
In this paper,the application requirements of vehicle navigation systems(VNS) for digital maps are analyzed first.Then the use of digital maps in VNS and some of its technologies are described in detail.The realization of many functions of VNS depends on digital maps and also puts forward some special requirements for the digital maps.It is necessary to set up the digital road map database of vehicle navigation oriented digital road map database.Some attributes of this kind of digital map database are discussed in this paper.In various kinds of VNS,the basic application of digital map is displayed.It can offer information to the user directly on the screen.In order to display the digital map onto the screen and change the displayed map quickly with the movement of the vehicle,the organization of the database is very important.A scheme on the organization of the database is presented in this paper.Some technologies of digital map display are also described.Because of the poor positioning precision of GPS and other positioning methods,the displayed position of the vehicle is often inaccurately out of the road.So the technology of map matching(MM) is widely used in VNS to improve the accuracy of positioning and the display result.A practical improvement of MM algorithms is presented in this paper.Lastly,a suggested multi-level organization scheme of digital road map database is proposed and discussed.
Usually the high precision GPS network lasts two or more years.In this period the GPS observation epoch,GPS satellite situation,GPS receivers,observing environment,the reference frame of ephemeris and even the surveying standard have changed,which will cause complex systematical errors.In this paper,all kinds of systematical errors of stochastic model in adjustment are discussed in details.And the relative adjustment model to estimate the systematical error parameters is established.In practice,the whole network is usually divided into some sub-nets,and each sub-net must have some systematical errors.With the different systematical errors,the theoretical estimation model,relative arithmetic and the statistical proof-test methods of systematical error parameters are also discussed in details.
The paper introduces three kinds of GPS timing and time transfer method.In this paper the principle of GPS timing for power system applications is also introduced,which includes synchronous voltage phase-angle measurement,power line fault location,synchronous sampling,online network consume account and energy management system(EMS).Especially,Two kinds of method are addressed detailedly.The paper gives the sketch of fault location of the two kinds method,and some test results are shown.Simultaneously,to confirm which power line causes the fault,various power lines have been taken into consideration.
Sage filter can simultaneously estimate the expectation values and the corresponding variance matrices of the unknown system and measurement noises.But in practice,we find that there are often constant biases in the results of the classic sub-optimal Sage filter,caused by the inaccurate estimation of the noise expectations.So a novel structure of two parallel filters that proceed simultaneously is presented in this paper.This new structure can not only eliminate the result biases of the classic sub-optimal Sage filter but also provide a more improved accuracy.In addition,SPRT method is used to control the adjustment of the noise statistics,so as to ameliorate the tracking performance of time-variant noises,however,the classic Sage filter does not suit the dynamic system of time-variant noises.Furthermore,the calculation burden is released and the numerical stability is improved by applying SPRT.Then a completely new parallel sub-optimal Sage adaptive filter is provided in this paper.The specific characters of the new filter can be summarized as follows:1) There are always constant biases in the results of classic sub-optimal Sage adaptive filter,so a parallel filter structure of adding a concomitant filter is designed to eliminate these constant biases;2) SPRT testing method is applied to the above parallel structure to test whether the statistical properties of the model noises are disturbed or not,so as to control the adjustment of the statistics.Then the filter's performance of tracking time-variant noises is significantly improved and the calculation burden is also released.In a word,the new adaptive Sage filter attempts to innovate the standard sub-optimal Sage filter,and make it practical.
In this paper,the working principle and characteristic of Georobot are briefly introduced,and then its application to deformation monitoring system is mainly studied.A main frame of the deformation monitoring system based on Georobot is presented and the corresponding software is designed.A special method which can effectively improve the monitoring precision of the system is applied in the data processing.The whole Georobot deformation monitoring system consists of base station(Georobot station),reference points,target points,computer and software.The software in VB environment mainly comprises the following functional modules:project managing,system initializing,learning measure,data querying,data processing and results outputting.Lastly,two experiments have been conducted by the Georobot deformation monitoring system which is developed by the authors.The result of the experiments proves that the Georobot deformation monitoring system has several advantages,such as high efficiency,high automation,real-time,high precision etc.
When the functional model of a surveying adjustment problem contains model errors or the measurements inherit systematic errors,especially when this kind of errors can hardly be described by a few parameters,conventional adjustment method of least squares can not correctly identify this kind of errors which will affect estimations of the unknown parameters badly and sometimes even give a false conclusion.This paper solves this problem effectively by introducing the semiparametric estimate model into surveying adjustment theory.Actually the semiparametric model is the conventional G-M linear model adding a nonparametric.Because there are more unknown parameters being added,the method of least squares can not provide a unique solution.This paper presents a semiparametric adjustment method fit for the general case.The calculation method is discussed and the corresponding formulas are presented.Finally,a simulated adjustment problem is constructed to explain the method.The results of the semiparametric model and G-M model are compared,which demonstrates that the model errors or the systematic errors of the observations can be detected correctly by the semiparametric estimate method.
Generally,under the Gauss-Markov model L = BX +Δ,the least square estimators of the parameters X = N -1 BTL possess some nice characters.In surveying,especially in dynamic GPS surveying,ill-conditioned problems may be encountered.When the surveying system is morbid and then the characters of the least square estimators become bad.Adding a diagonally matrix K to N will improve the state of N and then decrease the total variance of the estimates.Recent investigations of ill-conditioned problems have demonstrated that ridge-type estimation methods provide increased solution accuracy over conventional estimation techniques.That the generalized ridge estimate has less mean square error than the least square estimation.Naturally,the gotten estimators is expected to reach the minimum of mean square error.Because the mean square error of estimators is the function of K ,we should fix K depending on the minimum of the mean square error.On the basis of this idea,this paper brings about a method to solve the above problem,which is called direct solution to generalized ridge estimate(DSGRE).With DSGRE,we can obtain the optimal solution(that possesses the minimum of MSE) to the generalized ridge estimate directly and the ridge parameters K needn't to be calculated.
The structured light industrial surveying with high accuracy(e.g.±1mm) based on laser theodolite with three freedoms of rotation is particularly applicable for texture-lacking objects,such as capacity of oil tanker,external form of airplane and ship etc.As we know that certain instrument(such as Leica Profiler 4000) can not be used for this kind of objects,because its standard error(±5mm,even more) does not satisfy the accuracy reguirement.In this paper the scanning equation of plumb plane and the scanning equation of circular cone are firstly deduced when the laser theodolite with two freedoms of rotation is used.Then some scanning equations are briefly deduced when the instrument with three freedoms of rotation is used.These equations include the scanning equation of huperbolid of one sheet generated by rotating around the vertical axis(host axis),the scanning equation of huperbolid of one sheet generated by rotating around the horizotal axis(countershaft axis),and the scanning equation of plane for given orientation generated by rotating around the third axis.According to these planes and surfaces of known position and orientation in space,the space coordinates of unknown points could be determinates,and just one angle-measured instrument(or one CCD camera) is needed.The accuracy obtained by using this system(through the intersection) is much better than the accuracy by using the total station without reflector,(such as TCR,Leica).Furthermore,the system consists of a laser-theodolite,an angle-measured instrument and a portable computer,so it belongs to"toy bricks type" and it is quite cheap.It is also emphasized that the mathematical models in this paper could be used as designing model of certain laser scanning system.
In industrial manufacture,the shape quality of every division affects that of the whole object.This paper presents a means to control the quality of every part and simulate assembly on PC computer.The principle,inspection index and contents of the means are described in detail.Especially,a concept of distance in normal on ellipsoid surface as index of shape quality inspection is presented.
Taking Jiangsu as an example,this paper discusses the purposes and technological features of data updating and integrating in detail.Technological features are:·synthetical use of multi-sources data including SPOT-P and TM multi-spectral fusion image,GPS surveying road data,old 1:50 000 scale topographic maps and so on.·making scientific and advanced criterion according to the study area and the new development of geomatics.·application of 3S technologies to the data updating and integrating.Lastly,the paper discusses not only the source of error in the process of updating and methods of error control but also the feasibility and drawback of updating and integrating ways applied in this paper.
According to analyzing the features of annotation of spot elevation,this paper gives a method of identifying elevation annotation of a scanned topographic map and discusses the principle of the method,including separating character series on the basis of morphologic translating and cutting apart single character on the basis of vertical projecting.Finally,there is a performance evaluation.
Feature matching is an effective method for image matching.Some transform parameters need to be solved after the matching.This paper puts forward a new idea to solve the parameters.All the details are discussed in this paper.This idea and method is applied to dynamic DEM matching experiment.
This paper presents a new method of color digital remote sensing image processing based on irrelevant color space.A new algorithm is also proposed to implement the color space transformation which will reduce color loss.This paper shows an application of the new method to in the field of mosaics assembling technology.True color remote sensing imagery has been applied to more and more areas such as town planning,environment protection and large scale atlas renewal.The improvement is partially attributed to the efficient way of obtaining instrument and the enhanced precision in remote sensing imagery technology.Traditional imagery processing methods can not process three relevant heft heft of red,green and blue.The new method presented in this paper shows an effective way of handling the problem.
This paper analyzes the basic methods of data acquisition,discusses the main designing thinking,methods and technology on long-range intelligent data acquisition and processing system and implement the design of multi-point data acquisition and processing system.
The conditions which guarantee the nonlinear nonautonomous circuit to behave as unique steady state are very important and complex.For the nonlinear dynamical circuits with linear resistors,the problems have been solved by previously published papers.But for the network with nonlinear resistors,there have not been satisfactory results to deal with this problem.On the other hand,almost all the known results are not developed particularly for the high degree circuits,So people always find those results very difficult and inconvenient,or even impossible to utilize.The unique steady state of the dynamic circuits with nonlinear resistors in decomposition forms is studied in this paper.The adapted method is the matrix decomposition technique and Liyapunov functions.When handling the large-scale nonlinear circuit,it is very difficult or even impossible to determine its unique steady state directly.Therefore,in this paper,the large-scale circuits are decomposed into several sub-networks with comparatively lower degree,which can be relatively easy to deal with.The stability of each sub-network is determined by Liyapunov functions.And the unique steady state of the nonlinear circuits as a whole is deduce by a Hurwitz matrix,the elements of which are composed of the coefficients related to the stability of the sub networks.The main results obtained in this paper show that the unique steady state of the dynamic circuits with nonlinear resistors in decomposition form can be determined by the stability of some decomposed matrixes.Compared with the known results,the conclusions obtained in this paper make progress at least in the following two aspects.One is that this paper focuses on the nonlinear resistors'functions in the nonlinear circuit and develops an effective method to deal with them,and other is that this paper pays special attention to the handling of the high order circuits,so the results in this paper are very simple and convenient to use,when high order networks considered.From the above,the work in this paper is a great extension of the known results.