2000 Vol. 25, No. 6
Repeated GPS surveys in North China provide a direct measurement of current crustal motions.GPS surveys have been carried out in the region in 1992, 1995, and 1996 respectively by the First Crustal Deformation Monitoring Center (FCDMC)of the China Seismological Bureau (CSB).The velocity field are derived at 16 permanent stations in east Asia and 68 campaign mode sites in North China by using GAMIT software (King and Bock, 1995),GLOBK software (Herring, 1995)and QOCA software(Dong, et al, 1998;Shen, et al, 2000), and the North China region is moving at about (5~11)mm/a±1.8mm/a eastward relative to stable Eurasia.The horizontal crustal deformation and tectonic activity have been studied by using of GPS measurements.GPS measurements also offer a magnificent tool for measuring tectonic strain rates, which are assumed to be indicative of earthquake potential.The strain on the earth surface (ellipsoid surface)is calculated directly from above GPS velocity.Earthquake potential is of ten estimated from strain rates using Kostrov's (1974) formula, which essentially states that the moment rate inferred from geodetic straining can be equated to the moment rate to be expended in earthquakes.The seismicity in North China is of relatively high level either in its frequency or in its intensity.Since the beginning of historical records up to now, there were 127 earthquakes of M ≥ 6 occurred, and about 34 earthquakes of M ≥ 6 occurred in the Capital Circle area.The probability of earthquakes in a few years is discussed according to the geodetic st rain rates and earthquake st rain rates in North China area.As a result, the deformation rates from seismic moment tensors and from GPS velocities are basically agree with each other.The max principal strain rate and min principal st rain rate is 2.5×10-9/a and -2.1×10-9/a from earthquake moment tensors, and 2.2×10-9/a and -6.1×10-9/a from GPS velocities, respectively.It is viable for analyzing earthquake potential by comparing with geodetic strain rate and seismic strain rate.There is no strong earthquake potential (>M7)in the North China area, but there is about M5 earthquake potential in few years.Maybe the earthquake will occur in Tianjing-Beijing-Tangshan deltoid region and Zhangjiakou-Datong region because there are of high shear strain rate and they are also of compression surface strain rate.
In the ordinary operation of GPS kinematic surveying on aerial triangulation,a long-time static initialization is necessary to solve a correct ambiguity before the start of the flight.Even as we know,the static initialization is a time-consuming,costly,and difficult procedure.Sometimes the flight mission has also to be interrupted and the static initialization must be executed again because the cycle slip in carrier phase measurements is created.In order to obtain continuous records of GPS signals,we stipulate some constraint norm for the aerial photographic flight of GPS blocks.In fact,this is harmful to the actual application of GPS-supported aerotriangulation.Therefore,it is important and urgent to investigate a kind of approach of camera air positions determining by differential kinematic GPS positioning with ambiguity resolution on-the-fly (OTF).This paper will describe such an approach adopted in our practice.Firstly,we use a recursive algorithm of phase smooth based on the carrier phase difference between adjacent epochs to get the smooth pseudo-range of the C/A code measurements at each epoch.Secondly,we solve a float estimation of ambiguity for the double difference carrier phase's observables at a strip using the above smooth pseudo-range.Finally,we determinate 3D coordinates of the exposure centers of the airborne camera by means of the obtained ambiguity solution.This approach is implemented strip by strip instead of whole block.It does not consider the cycle slips happening during the turn around from one flight line to the next,so that the aerial photography is able to perform in the conventional operation specification.For testing the accuracy of positioning projective centers of airborne camera by the above method and efficiency of GPS-supported bundle block adjustment,a set of actual aerial photos with GPS data taken from Tianjin project was selected and processed by software DDKIN (DGPS dual frequency kinematic surveying) and WuCAPS GPS (Wuhan GPS-supported bundle block adjustment).The achieved results have shown that our proposing scheme is feasible as well as the overall accuracy of GPS-supported bundle block adjustment is closer identical between ambiguity solutions initialized on the ground before taking off and resolved on the fly.The OTF algorithm,however,will greatly relax the operational constraint for the aerial photographic flight of GPS blocks and be of great importance to apply widely GPS-supported aerotriangulation into practical production.
The precision of GPS monitoring deformation for Gehey an Dam is much lower than that of others under the ordinary conditions.Therefore, how to process the data of Geheyan Dam is not only a difficult task, but also a real challenge for us. By analyzing the result s of another reference station,GPS2,we found that there are some differences among the ones of each session, thus it can be seen that there are some errors in the procedure of data processing.It is difficult to deal with these errors.On second thought s, we compute the relative coefficients of GPS2 for each deformation monitoring station, and get a fact that there are strong relativities among GPS2 and monitoring stations.Therefore, we can use the data of GPS2 to lower or eliminate the errors of the deformation monitoring stations. Based the above,we put forward the method as follows:First,make the best use of a mass of raw data owing to around-the-clock observation and use Filtering Method to get rid of gross errors and noises of the deformation monitoring stations.Second, use Integral Adjustment Method to get the result s.It is the critical approach to get a good result.We adopt different weight values for different types of stations, the deformation monitoring stations are endowed with small weight values;GPS2 is endowed with relative to much bigger value;and GPS1 is endued with infinite, i.e. GPS1 is fixed.We cite an example in this paper which proves that the above method is right and feasible.
It is a very important work to analyze the working datum marks' stability for GPS deformation monitoring system.After the system working some period of time,a large amount of deformation observation data can be obtained,and these data can be described as one time series.If the datum marks is steady-going during this period of time,the time series of the observed data should be an ergodic stochastic series and cohere with the condition and nature of a stationary stochastic process. The autocorrelation function is one of eigenvalues of the stochastic process,it reflects the relativity of observations in different time.If the stochastic functions are not correlative,the estimation of their standard autocorrelation function should tend to zero when the time tends to infinity.Hereby,we can identify whether the studied time series is ergodic or not.In addition,if the stationary stochastic process contains periodical components,its autocorrelation function has periodical components as well,and the periodicity of both is same. [FK(W20。40ZQ] Generally speaking,the observed data of GPS deformation monitoring system is very difficult to be equally spaced,occasionally missing data within quite a length time,by reason of the influence of various factors (subjective and objective).The frequency spectral analysis is a quite efficient method to analyze periodical signals,but its prominent limitation is that the data must be equally spaced.For this reason,in this paper the spectral analysis is only applied to identify whether the time series has periodical components or not.If it contains periodical components,a higher order polynomial is used to approach the data series by the leasts-quares method.The practice testifies that this method is grealy effective which is applied for describing the long periodical alteration of the time series. Taking GPS automatic monitoring system of outside deformation for Geheyan dam on the Qingjiang river as example,this paper analyzes the deformation characteristics of tow working datum marks for this system.Results show that in vertical component,there is a small linear displacement trend with yearly 1.64mm,and a long periodical deformation trend with about one year;in horizontal directin,the linear displacement trend is not distinct,but there are also the deformation characteristics of a long periodical trend.In order to test and verify above results,the random data generator is employed to simulate the random data series,the end results are coincident.The research indicates that the small linear displacement trend included in the time series'errors can be identified by the time series' data of large sample quantity.
The airborne laser sounding system will become an advanced equipment in surveying water depths and detecting underwater targets and possible hazards in the water in 21 century.It is being made cooperatively by Chinese research units to survey Chinese sea-water territories. When making the airborne laser sounding system it is necessary to distribute carefully the accuracy specifications for its subsystems.According to our research the accuracy surveying sea-water depths relates not only to the self-system errors, but also to error sources from the airborne auxiliary equipment.This paper focuses on two error sources influencing on a sounding accuracy:1)auxiliary errors resulting from the airborne accelerometer and sweep equipment; 2)errors surveying sea-water depths by means of the airborne Laser sounding system. Especially, it is pointed out that multicolor laser can be used to determine effectively the refractive corrections in the sea-water, so as to mitigate an influence of the refraction index error on the sounding accuracy.
The national gravity network to be built is composed of 100 points,15 absolute gravity points and 85 relative gravity points,and nearly 200 observations.This paper evaluated the primary scheme firstly.Considered the target of optimization design for precision,reliability and cost,some principles that were suitable for gravity network designing were proposed.During the first order optimal designing,the simulative method was used to find and delete the observation which had little influence on the precision of the network.After that we got a scheme whose precision was little lower than that of being required.Based on this plan we used the analytic method and simulative method to do the second order optimal design and got tow schemes.Both of the schemes satisfied the requirement of precision and had a higher reliability and a lower cost relatively.
The method that hydrodynamic models are reconciled with observation,e.g.altimeter and oceanographic data,is called as data assimilation. Calculating coastal stationary sea surface topography with altimeter and oceanographic data,called as combination problem for short,is a technique of data assimilation,which is one of the front research area in altimetry. In this paper,the basic equations are integrated in the vertical direction with approximation of Boussinesq and quasi-static on the basis equations of liquid dynamics. And then an elevation-mode of steady current and its solid boundary condition are derived with a reference geoid as reference surface. Observation equations are formed using finite difference method from the elevation-mode of steady current and its solid boundary condition with stationary sea surface topography as observation value and the square root of onflow friction coefficient as parameter,and the combination problem is solved with parameter adjustment. In the end,stationary sea surface topography of Eastern China Sea,in 22°N~41°N and 116°E~131°E,is calculated with T/P and ERS-2 altimeter and oceanographic data.It comes to the following conclutions from this paper: (1) Sea bottom relief and sea density field are main influence on stationary sea surface topography.(2) The reference geoid error the wavelength of which is longer than size of the selected area can not be eliminated by the parameter adjustment because the observation equations are finite difference of stationary sea surface topography. Hence,reference geoid is used to fix stationary sea surface topography the wavelength of which is longer than size of the selected area in this paper.(3) There is a denseness isoline whirlpool of stationary sea surface topography around entrance of the Changjiang River. The isoline near Liuqiu archipelago are disorder. There is a denseness isoline southwest Liuqiu archipelago,which could be relative with Taiwan Kroshio.
The classical dynamics model of polar motion is linear and its solution is of elliptic orbit.But there are excitations and damping in Chandler wobble, since the excitation function is not very stable.The damping and excitation cannot be made both ends meet in each period, too.So Chandler wobble may not follow elliptic orbit, instead its orbit should be spiral.The real posit ion of CW shows ro tating in a broad area.Of course, may be Chandler wobble reserves energy lossless in long time.However, at least in limited observations,Chandler wobble does not possess close elliptic orbit.No other than the damping and excitation are balanceable, the orbit may be elliptic.In this paper, spiral mot ion equation of Chandler wobble is deduced from combination of displacement in tangent and radial direct ions.In fact, the frequency series of CW is not stable on the inherent frequency.There is difference between the real frequency and the inherent frequency.The difference must be caused by the in-stable ex citation.Considering that the CW complex amplitude may be represented by the vector sum of the tangent and radial components, the complex amplitude is written as the vector sum of two terms, one is the free sway and the other is the common action of excitation and damping.Spiral orbit of Chandler wobble is better solved and coefficients of logarithm spiral equation are at tracted empirically.The amplitude of CW logarithm spiral equation is provided as ±5.4% per period, here the plus represents spiraling-out and the minus spiraling-in. The average spiral displacement amplitude of each Chandler period is given 6.75 milliarcsecond (mas),meanwhile 20 mas to -30 mas in maximum.Since the logarithm spiral parameter is instable one, it can be used empirically.Applying the empirical logarithm spiral equations to deduce Chandler amplitude, the square error with respect to the observation amplitude is only 0.0275 mas.On the other hand, the time series of the spiral displacement of each Chandler period shows an irregular process.By this time series, the inherent free sway has been moved away and remain signal should be from the excitation function.The act ion of excitation may be attracted mo re easily from the spiral amplitude moving away the average ellipse of the ideal orbit of Chandler wobble.
The grade of land in the city zone is affected by nature and society position plus communication condition.The process of land grading is to get the fixed quantity of all conditions and to classify all the land parcel to be evaluated。It is important to get the effect value from that the evaluated land parcel is affected by the grade factors in the process of land grading.Same type factors' effect attenuates with the increase of distance between grade factors and evaluated land parcel.The attenuating rule is called distance-attenuating formula.Traditionally,the distance between grade factors and evaluated land parcel is the length of spatial line from the center of factors to the center of the land parcel when the effect value of grade factors is calculated.It ignores the obstructions between grade factors and evaluated land parcel.So the graphs that effect value is represented are a series of contour lines with attenuating effect value.In people's custom thought,the distance from here to there is the distance along the road instead of the spatial distance.So it is more reasonable to use the distance along the road than to use the spatial distance in land grading.In this paper,the shortest path method in graph theory used in urban land grading is discussed.The distance between grade factors and evaluated land parcel is calculated by the shortest method.The effect value of grade factors in each unit is gotten by the distance-attenuating formula.Based on the value,the more reasonable land grade of each unit can be reached.
This paper presents a cadastral spatial data storage structure based on relational database, and the procedure of its realization.This paper consists of three parts.In the first part, some existing problems in old cadastral spatial data storage structure are discussed.These problems include:①the security of cadastral spatial data is difficult to be assured of;②the change of cadaster is difficult and the integrality of cadaster is difficult to be assured of;③ there exist in some problem transmission of cadastral information and its share;④ the efficiency of data access is low.In the second part, the feasibility of using relational database to store spatial data is analyzed and a new cadastral spatial data storage structure is presented.At the same time, the related table structures and its field descriptions are given, the merits and demerits of this storage structure are analyzed in detail.In the last part, through a real example, the detailed method to make the new storage structure realized are given.Moreover, some key techniques to make the new storage structure realized are discussed.These techniques include:①the application of database transaction;② the application of database trigger;③the secure recovery of database.
Different from traditional building modeling from aerophoto, a building modeling method, which is called CSG block analyzed method from ground photographs,is presented in this paper. We use CSG as the primary representation, which describes each building by a combination of one or more basic primitives for visualization purposes. Based on Debevec semi-automatic modeling algorithm, this method measures building directly with CSG block analysis,so enhances the reliability and practicality through giving attention to operator intelligence and computer efficiency. Our modeling approach has two components.One is a semi-automatic modeling method which facilitates the recovery of the basic geometry of the photographed scene. The algorithm exploits the constraints that are characteristic of architectural scenes.The other is view-dependent texture mapping, a method of composition multiple views of a scene that better simulates geometric detail on basic models.The results show that the approach has the ability to create the realistic building modeling.
A new airborne remote sensing sy stem——3D image, which integrates GPS, attitude measurement unit (AMU), scanning laser ranger finder (SLRF)and spectral scanner, has been developed successfully.The scanner and SLRF use the same optical system, which ensures the laser point to match the pixel closely.The distinctive advantage of 3D image is that it can produce geo-referenced image and DEM (digital elevation models) image without any ground control points (GCPs).Because surveying GCPs is no longer necessary, it is the software that processes the data and generates data products.Therefore, its efficiency is 10~100 times higher than traditional approaches.The data acquired by 3D image can be processed to produce several kinds of image, such as DEM, geo-referenced image.The data processing involves data decomposing and checking, GPS processing, calculating the positions of laser points, producing geo-referenced image, producing DEM, strips mosaic.The principle of 3D image is first introduced in this paper, and then we focus on the fast processing technique and algorithm.In the end, the data acquired by 3D image in the east of China is processed based on the basis of fast processing technique, and the result shows that the processing technique is feasible and can meet the requirement of quasi-real-time applications.
There exist abundant multi-metal grains in over 5 000 m deep sea floor.In order to exploit the deep-sea floor mineral,we have taken some deep-sea floor pictures for study.Fig 1 shows a typical picture.There are dark metal grains pixels (the target objects),and grayer sands pixels (the background objects).Point light source is necessarily used when we take pictures for it is very dark in deep-sea floor.However,it causes serious non-uniform illumination in these pictures,which enlarges errors when measuring grain's radius and calculating mental conservation. [FK(W27。40ZQ] Three simple methods are developed in this paper for removing the non-uniform exposure effects.(1) Local enhacement and filtering.By setting appropriate parameters in the filter,we can force the brightness and contrastness of pixels in a local window into appointed target mean grey and contrast value.As a result,the brightness and contrastness will be improved in insufficient exposure area,partly reducing non-illumination effects.(2)Substracting the source image from the background image,which merely consist of sands pixels by extracting the local maximum grey value.It is not easy to decide the local window size to make it appropriate for not only being large enough to contain at least one pixel of metal grain and one pixel of sands but also being small enough to make the intensity of the point light source distributed approximately equivalent inside this local window.Generally,it changes with the size and density of metal grains in digital image.After image substracting,most of the effects of non-uniform illumination have been removed from the deep-sea floor pictures.(3)Statistical fitting grey distribution and stretching.First we calculate the local maximum and minimum grey value all over the image using the above second method,then fit two planar cubic equations with these statistical data,and then based on the fitted data all over the image,stretch the gray value pixel by pixel. Theoretically,the third method integrates the advantages of the second one,and can completely remove the effects of non-illumination from the image.For analyzing and comparing the transformation of grey value before and after each processing step,we give the trendlines of grey value of pixels in line 263,which reflects the one-dimentional grey and contrastness distribution characteristic in these pictures.From the trendlines,we can draw a conclution that the last approach is more effective than the other two in removing point light source exposure effect from deep-sea floor pictures.In a word,though we do not make use of the ideal model of point light source in the whole experiment,we have also solved the problems.The approaches employed here demonstrate the effectiveness and practical significance.
Wi th the development of spatial technology, computer technology and photo-electricity technique,microwave remote sensing becomes one of the advanced fields of remote sensing.Many countries invest a lot to develop SAR(Synthetic Aperture Radar) which possesses the ability of penetrability and can acquire data in all-weather and all-time. Topographic information is important in many geographic applications.Synthetic Aperture Radar (SAR) is a kind of imaging radar capable of producing high-resolution images in all weather and all-day conditions.But it usually needs image pair or more images to generate DEM from SAR imagery, such as interferometric SAR (InSAR) and radargrammetry.The imaging conditions (look-angle, space baseline, for acquiring the image pair sometimes are very difficult. SAR is a side-looking imaging mode and its image is very sensitive to the terrain shape.The tittle undulation of the terrain may induce the change of the image gray distribution and/or the texture characteristics.In this paper, the radarclinometry for extracting the earth elevation from only single SAR image is investigated,which is based on the shape-from-shading principle developed in computer vision.Firstly, the approaches for generation of the digital terrain elevation from the SAR image data are discussed.Secondly, the method of radarclinometry will be briefly described.The elevation reconstruct ion relies on a Lambertian assumption for the terrain backscatter model.Then a single-line integral process is applied to calculate each pixel altitude, but it is still contaminated by noise.Finally, the multi-line integral processing with various directions and the simulated annealing algorithm are respectively introduced to improve the single-line integral processing result.The presented experiment results are promising in many geographic applications.
Close-range photogrammetry is to determine the shape and size, of the object,in stead of it's absolute position.Therefore, at first, any translation and rotation of the photogrammetric model of the object caused by whole geodesic, photographic and photogrammetric procedures in close-range photogrammetry could not be considered,in other hand, it is necessary to analyze the all reasons which cause the deformations of the shape and size and to present their corresponding theories and equations. This situation, of course, is very different from the conventional topophotogrammetry. In this paper some specific charateristics of limit errors in close-range photogrammetry are presented in detail,including limit errors for calibration of interior elements for close-range cameras, the limit errors of relative and absolute orientations in close-range photogrammetric procedures, and the limit errors of control works in close range photogrammtry. A theoretical equation of calibration accuracy for close-range camera is given. Relating to 3 examples in this paper, their theoretical accuracy requirement of interior elements of camera change in the scope of ±(0.005~0.480)mm. This discussion permits us to reduce accuracy requirment in calibration for an object with small relief,but the camera platform was located in violent vibration environment. Another theoretical equations were also presented for control works in close-range photogrammetry, among them there is equation of relative RMS of base lines (mS/S), and the equation RMS of start direction. It was proved that the mS/S could be equal to the relative RMS of mΔX/ΔX. It was proved as well that the permitting RMS of start direction is much bigger than the consistently using one. Some useful equations of limit errors in close range photogrammery were presented as well.Above mentioned suggestions are perhaps beneficial for increasing efficiency,for reducing production cost.
This paper makes a great investigations, analysis and researching on color digital images and the modeling theory of analytic hierarchy process.Based on the theory and principle of color reproducing in color digital images copy process,a index system evaluating the quality of digital images color reproducing is presented. Referring to the national or trade standard, a relative judge standard of qualitative and quantitative index is given. Using the analytic hierarchy process in mathematics, it establishes a mathematics modeling of quality synthetical evaluation of digital images color reproducing, and designs a set of mathematics methods of synthetical evaluating color copying and processing.Finally,using VB to design panel,it basically realizes the simulated evaluating color digital images in computer,gives a systematic and fixed quantity way for color's reproduce for color digital images.
Web technique, which changes the exploitation and the implementers of enterprise's application system, is an important part of Internet/Intranet.Database technique is the basic tool of information management and effects on the basic core.Metabolic operations need new capability requirement for database application.In pace with the competitive superiority of Internet/Intranet, enterprise affronts the new operation challenge.So the combination of Web technique and database technique-Web-db, emerges, as the times require.PowerBuilder has mightiness exploitation function for database and lo ts of big model enterprises have used it to exploitat management information system.So, it is a significative research task in the field of computer application that how to use Web technique to include PB application software, traditional MIS and intrinsic invest in Web.It can realize the conversion between traditional MIS exploited using PB and Internet/Intranet information system.The research will exert greatness potential of information resource. On the basis of the meaning of Web-db and the point that integrating Power Builder application software in Web, this article brought forward three kinds of solutions.One is to use browser to visit database in Internet.Its typical representation is commonality gateway interface and API technology.The second is dbms jointing Web at first hand regarding Web as base.Some manufacturers enlarge data type of database.All of the Web data types are regarded as dbms internal data types.The third is enriching local warehousing using Web resource.This method studies and uses data resource, including content in database and net page.Warehousing on Web and data mining on Web in literatures belong to this work.But, choosing which method to realize integrating Power Builder applications in Web needs to consider some aspects, including exploitation environment, client environment, the CPU capacity of server, the traffic and memory capacity of net. This article gave an ex ample of power supply bureau of Wuhan, based on it's net's characteristic and enterprise's characteristic, analyzed application's needs.Decomposing Web database application is as follows:dealing with complicated enterprise interior information and application, keeping existing system integrality and safely, and it's performance;issuing enterprise's information and data out the enterprise. This article put forward how to realize it.Firstly, choose Web server.The Web server needs kinds of sustain, face multimedia, suffice transiting application in Web,must have the tools to create net spot and manage it.In this solution,we choose IIS as our Web server. Secondly, using Web.pb, transplanted enterprise internal manages information system to Web.And listed its system framework.Here an example about how to include Intrinsic Power-Builder application in new application is given. Thirdly, using ASP technology issued internal information and data of enterprise.This can obtain really thin client and high performance. This system can achieve reliably affairs manage and rationalization.It has powerful database in the back end, deals with relational affairs, servers a mass of client s.Simultaneity, it changes old operational pattern of enterprise system.