2002 Vol. 27, No. 6
The CHAMP Wuhan tracking station is based on the frame between Wuhan University and GFZ.It is the 12th Ground Tracking Station for CHAMP mission.The establishment of CHAMP Wuhan is introduced in this paper.Then the application of CHAMP mission are described in detail.Last,the differences between CHAMP Wuhan and IGS Wuhan are described.
This paper proposes a strict geometric model of the calculation for the position and orientation parameters of the remote-sensing image with higher resolution.The method adopts threesteps of transformations based on parallel ray projection.The first step is reducing the three dimensional space to the image space by the similar transformation.Then,the small space is projected to the level plane,which passes the center of the image plane.Finally,the level image is transformed to the original declining image.Every step of the model is strict,and the map function of each transformation is the first order polynomials.The final calculation of the parameters is for the linear equations with good status.As a result,the problem of the relativity of image parameter calculation is solved completely.Some experiments are carried on for a lot of images with 10 m,3 m and 1 m resolution.All of the results are quite perfect.Thus,the validity of the strict geometric model has been verified.
The traditional algorithm for automated map name placement and its disadvantage are firstly analyzed in this paper.A new global optimization algorithms that called genetic algorithm is put forward to solve the point-labeling problem.According to the properties of map labeling,the basic design schemes and strategies of applying genetic algorithm to solve the map name placement is detailed in this paper.First,an integer vector coding scheme is adopted in the algorithm,which uses an array(or string) of integers to represent a configuration of map labeling.The initial strings can be obtained randomly by generating a random integer in a specified scope for every element(gene) of all strings.Then a fitness function of map labeling is represented as a quality evaluation function of map labeling Lastly some typical experiments are elaborated and some results obtained by the automated map-labeling program based on genetic algorithm are presented.In the meantime,a comprehensive experiment is conducted to compare this algorithm with climbing algorithm,annealing algorithm and Hopfield neural network method,and experimental results have shown that the performance of genetic algorithm is superior to those of other several traditional algorithms.
A flexible camera calibration technique using 2D-DLT and bundle adjustment with planar scenes is proposed in this paper. The equation of principal vertical line under image coordinate system represented by 2D-DLT parameters is worked out using the correspondence between collinearity equations and 2D-DLT. Proof of ambiguities in camera parameter decomposition with 2D-DLT parameters is given. Initial value of principal point can be obtained with at least two equations of principal vertical lines. Proof of critical motion sequences(CMS) is also given in detail. The practical decomposition algorithm of extrinsic parameters using initial values of principal point, focal length and 2D-DLT parameters is discussed elaborately. Planar-scene camera calibration algorithm with bundle adjustment(using collinearity equations) is addressed. For the proposed technique, either the camera or the planar pattern can be moved freely, and the motion need not be known. Very good results have been obtained with both computer simulations and real data calibration.
This paper proposes the concepts of multi-dimensional co-correlation coefficients and density of co-correlation coefficients between pixels of remotly sensed multi-spectral image.The applications of these concepts to simulative images show that the edge information can be extracted.The minimum co-correlation coefficients and the difference of them can provide evidently the information of the position and strength of edges,which implies that the analysis with co-correlation coefficients can be used for edge extraction of multi-spectral image. The further experiments have been performed using TM images.The different results with different value ranges of minimum co-correlation coefficients and the difference of them indicate that we should select the rational threshold of co-correlation coefficients for edge extractions.Finally the paper concludes that the analysis with co-correlation coefficients for edge extraction of remotely sensed multi-spectral images is quite effective.
This paper develops new methods to detect the adjusting parameters for digital image distortion,and to determine the elements of interior orientation of cameras.The mean square errors of photo coordinate is lower than 2.5 pixels.A new manner of digital photo geological logging and its principle are introduced,so is a practical system developed by the authors.This paper also discusses the geometric precision of photo geological logging for tunnels.Theory and practice prove that the precision of photo logging can be effectively controlled by use of a digital orientation-camera based on a normal digital camera,that digital orthophotomosaic obtained from original photos can be used as logging base-map,and that photogrammetry based on a normal digital camera can also be used to measure geological elements of attitude of layers.
This paper proposes a method for image threshold segmentation using multi-scale space analysis.Multi-scale space is obtained through multi-scale filtering to original histogram of luminance.On the analysis of multi-scale space,the range of filtering scales is determined so as to avoid scales continually increasing/decreasing and improve the efficiency of algorithm.Then the original histogram is filtered by coarse-fine scale in the determined range of scales.Locations of significant inflexions at different scales can be obtained as thresholds by computing the second difference of the filtered histogram.Accroding to the number of inflexions at the largest scale and inflexions corresponding to graylevels,the fine locations of inflexions at the largest scale are obtained as thresholds.The result shows that the proposed algorithm is effective by contrast with other image segmentation algorithms.
ANN has been introduced in land use/cover change detection to improve the change detection results.In this paper,the input and output,the structure and reasonable settings of ANN have been studied and compared.Different ANN models and algorithms have been introduced to improve the performance of ANN.The results have shown that LVQ and MAALR(momentum-adaptive adjust ment of learning rate) have turned to be more efficient in land use/cover change detection than BPNN because they take less ANN training time and have no local minimum. The experiments based on TM satellite images of different time have shown that ANN method is practical and efficient for the change detection.The accuracy of it is higher than those of the traditional methods,and it can provide both changed areas and categories at the same time.Besides,it is easy to integrate multi-source data because of low demand for data distribution.
This paper re-defines the grounding line(GL) of Amery Ice Shelf(AIS),East Antarctica,utilizing radio echo sounding(RES) data.It was indicated that the GL southmostly extended to 73.2°S,about 500 km away from the ice front.Two representative profiles are selected to validate the above preliminary conclusion,by ratio of bed depth to ice thickness,and height divergence between the measured height and the calculated value according to ice thickness by hydrostatic equilibrium theory.Moreover,the conclusion is further validated by ERS-1 digital elevation model(DEM) gridded 5 km and RADARSAT Antarctic mapping project(RAMP) 1km-gridded DEM,and tidal noise detected by in situ GPS measurements.Finally,the floating ice region of the whole ice stream is illustrated according to the hydrostatic equilibrium theory.
Anatomizing the velocity field and definition of ITRF2000,we find that the precise of ITRF2000 frame is better than these of ITRF96 and ITRF97.ITRF96 and ITRF97 are defined through a weighted least squares algorithm with SLR,VLBI and GPS data equally, but ITRF2000 only uses VLBI and SLR data, excluding GPS data. Because GPS technique is deficient in definition of ITRF2000 origin,orientation and scale and rate, the accuracy of ITRF2000 is improved compared with ITRF96 and ITRF97 without using GPS data. However, the linear rates of change of ITRF2000 orientation angles are determined by only 54 sites imposing a geological plate model NNR-NUVEL1A to achieve no net rotation of global frame with respect to the Earth's crust.Analyzing the total angle momentum,we find that ITRF2000 also has net rotation with respect to the Earth's crust. In this paper, a new global plate motion model of ITRF2000VEL is determined based on the ITRF2000 velocity field.In order to achieve no net rotation of ITRF2000 frame, we calculate the total angle momentum | L | of ITRF2000VEL, 0.127°/m·a-1 to rectify in practice.
Regularization method is an effective method in solving ill-posed equation.In this paper the unbiased estimation formula of unit weight mean square error in the regularization solution is derived and the formula is verified with numerical test of 1 000 sample data by use of the typical ill-posed equation,i.e.the Fredholm integration equation of the first kind.
Reliability analysis and data snooping are important contents in quality control of adjustment system.Baarda's reliability analysis and data snooping method is designed for independent observations and it is quite consummate both in theory and in practice.But they are researched respectively and constitute different systems.In this paper,we establish a uniform basic equation used for reliability analysis and data snooping from verifying the ratio of variance,then the expression of reliability index based on the correlation weight is obttained.We also prove that the expression applied to find minimal model errors and the weight matrix is not restricted to diagonal matrix.When the weight matrix is diagonally,the redundant observations' inner reliability index ri is a particular case of Ri.The consistency proves that Ri is reasonable.At the same time,a new data snooping method is presented,which is related to reliability analysis measurement.The consistency of reliability analysis and data snooping both in theory and in practice is a new viewpoint,which will be used in other fields of surveying data processing.
This paper discusses the scale correction of electronic distance measurement instrument(EDMI).Some incorrect results measured according to"Verification Regulation of Electronic Distance Measurement Instrument JJG703-90" are given. The reason why R is incorrect has been analyzed.The problems related to verification regulation are explained.Revising the verification regulation and determining R by use of measuring frequency are suggested.
By analyzing and comparing the space conception of geography subjects,this paper discusses the space conception of the geographic information system,and points out that the space mathematics basis of the geographic information system has been the mathematics definition of the space conception of GIS.This paper has opened out and demonstrated the space mathematics basis of GIS.Hereby,it discusses a current hot topic-"the seamless space database" technology,and points out that what is called"seamless" is not only formal"the seamless visualization",but"the seamless measurement","the seamless space analysis" and"the seamless standardization integration".Finally,it disserts some of topics about space analysis theory and technology of"the seamless space database",space data expression,NGDF and technology route,movement geometry on Earth,environment and other problems.
At the present time, the database management system of some existing GIS or LIS is able to handle the spatial data efficiently, but these spatial data just describes the current states of entities or phenomena without any information about their past states. In practice, the past states are as important as the current ones for some special applications.A good decision should take the past and current states into account for the future plan.This paper tries to extend the existing GIS or LIS to support temporal information of entities as well as spatial information,and uses an example to show the detail about how to realize the extension and finish the change of land parcels.
In recent years,many researches are focused on the uncertainties of GIS data.It can be found that most of these researches are focused on the uncertainties of spatial data while a few are on the attribute data.In this paper,the authors try to integrate the uncertainties of spatial data and attribute data to analyze some problems on the data uncertainties in Census GIS.This paper suggests considering the uncertainties of spatial data and attribute data at the same time in GIS analysis and application.On the basis of the characters of Census GIS,the authors concludes three kinds of data uncertainties in Census GIS.Then,some related contents,reasons,and the influence of these uncertainties are discussed in detail.On the basis of the data uncertainties discussed in this paper,the authors propose some methods to resolve the related problems.Accordingly,some concise formulae are used to illustrate the uncertainties and the related models.
This paper presents a new and more effective algorithm to determine the directional relationship between arbitrarily-shaped polygons which is based on the rasterization of polygons and well conforms to spatial cognitive models.The results are identical to that of visual interpretation by human.Then the calculability of the directional relationship between arbitrarily-shaped polygons is discussed.And an approach to determine the calculability based on the number of zero values of the degree of membership of direction is provided.
In this paper, four statistical maps are designed according to a set of the same data and a related atlas, and the targets searching on these statistical maps are tested with the support of the cognitive test software compiled by ourselves.The results show that when we search the target in the statistical maps, the visual system might use parallel process model and serial process model, and the mean reaction time and the correctness of the target searching are affected by the two search models. The cognitive efficiency of the designs of the four statistical maps are discussed and analyzed.
On the basis of the theory on active and real-time database,this paper suggests an active real-time database system ARTDBS supporting advanced application,which perfectly integrates traditional DBMS capabilities,active capabilities,and real-time constraint mechanism.The active mechanism in ARTDBS is the trigger mechanism.Effective work of the triggers depending on design of the system execution model isanalyzed in detail,and an execution model of the trigger is developed based on WINDOWS NT environment.
In this paper,a diameter measuring technique of slender glass tube based on CCD assembling is presented.Since field of vision is very small,the cameras are calibrated with a grating.During the process of calibration the grating is placed in front of the lens and is imaged on the CCD.By determining the number of pixels of each span,the parameters we need can be calculated exactly.The diameter can be measured by performing some mathematical calculations of the edge position and the parameters obtained by calibration.The errors that affect measuring precision are analyzed.The precision of this system is less than 1μm.The experimetental result shows that the measuring system has quite high stabilization.Of course much improvement can be made to this method.A higher accurate edge-positioning algorithm can be used to improve the precision,and the employment of more advanced image capture card may make the measure result more stable and repid.
This paper introduces the present situation about IP network,methods for realizing it and prospect of IP network.Then we analyse the multimedia communication technique and applications for IP network such as video on demand,IP Phone and IP conference.Last,this paper explains the prospect and trend about the multimedia application of IP network. The technology of IP network is for group/packet exchange which is one non-facing connecting network.The ratio of using source of IP is higher than that of Switched Circuit Network(SCN) communication technology,and the expense of IP network is lower than that of SCN.Therefore people attach more importance to the research of IP network.At the same time,the operations of IP network technology come forth.We also find that the recent growth of IP networking technology has led to the need for tools that provide for the management of interconnected IP networks.Successive researches about the IP network are of important values and IP network has good prospect according to its advantages.