1999 Vol. 24, No. 4
This paper describes an integrated approach to the construction of textured 3D scene model of buildings from digital images. This approach is implemented in a collection of the global image matching and least Square template matching algorithms. At first, we use improved global image matching algorithm had on variable weight smooth constraint to get the dense disparity surface of the city and the height of every building. Then use a semi-automatic algorithm based on least square template matching to get the accrete edge of buildings. In this approach, the operator recognizes the building and give an approximate location of it in an active mode.The template matching approach automatically searches the exact location of the building's edge. Through this step,we get the vector data of every building in image. At last, we combine both the vector data and texture data in images to reconstruct the textured landscape of the buildings. The potential application include create reality model to be used in city areas and mapping in city area semi-automatically.
With the rapid development of aerial and space remote sensing technique, the digital camera has been explored,and mapping experiments with this kind of digital images are processing as the regular mode of aerophotogrammetry. On the other hand, the technique of integration of 3S (GPS,RS and GIS) and digital photogrammetric system have been put in actual use as a mature technique. Meanwhile, the information superhighway will be the new key technique in the coming 21 century. All these developments mean that for the spatial geographical data require muti-level remote sensing image data. In RS, GIS and DPS(digital photogrammetric system), one of key techniques is how to deal with the real time transmitting of huge remote sensing data and how to build image data base. So the investigation technique of compression of remote sensing data is a very urgent task. Normal data encoding technique comes to loss-less compression, while the compression ratio only ranger about 2 and can't be satisfied with actual requirement. The new developing compression techniques, such as wavelet compression and fractal compression will reach a high compression ratio, but they belong to degraded compression and need much more CPU time.So for the time being, these methods have not much actual use in the field of the remote sensing.In this paPer, the technique of guasi-lossless compression based on the image restoration is presented. The technique of compression described here will include three steps, namely, bit compression, removeing correlation and image restoration based on the theory of modulation transfer function(MTF). The guasi-lossless compression comes to high speed and the quality of reconstructed image under restoration reached the guasi-lossless level with higher compression ratio.The test of TM and SPOT remote sensing images show that the average compression ratio is about 4~5, the fidelity reaches 0.99 and Peak value signal-noise ratio(PSNR) is over 42. All of the results confirm that the technique is reasonable and applicable.
This research, by use of RS image-simulating method, simulated apparent reflectance images at senor level and ground-reflectance images of SPOT-HRV, CBERS-CCD, Landsat-TM and NoAA14-AVHRR's corresponding bands.These images were used to analyze sensor's differences cased by spectral sensitivity and atmospheric impacts. The differences were analyzed on normalized difference vegetation index(NDVI). The results showed, the differences of sensors' spectral characteristics cause changes of their NDVI and reflectance. When multiple sensors' data are applied to digital analysis, the error should be taken into account. Atmospheric effect makes NDVI smaller, and atmospheric correction has the tendency of increasing NDVI values. The reflectance and their NDVI of different sewn can be ed to analyze the differences among sensors features. The spectral analysis method based on RS simulated images can provide a new way to design the spectral characteristics of new sensors.
This paper introduces three main models(linear, logarithmic,and exponential model),which are used in monitoring the soil moisture at present according to the thermal inertial theory based on NOAA AVHRR data, and the processing steps of these models are presented in details.Three models are tested and validated by using ground truth data, then the environment which causes drought is also discussed in the paper by using ancillary data including DEM and landcover.The results show that three models meet the needs of the large scale drought monitoring, and that the application of ancillary data not only makes the quantitative analysis of drought distributing and its causes possible, but also validates the models correctness in a certain extent. The example,which uses NOAA AVHRR data and DEM and landcover data to monitor the drought condition in Hubei province on Nov. 12, 1998, gives that the terrain condition is also the main factor which affects the soil water content in southern China as well as the climate condition, and that the drought-against capacities of the different landcover types are of diversity. Forest is bot, woodland and grass take the second place and crop worst. Therefore, these conditions must be taken into account in monitoring drought in southern China.
In this paper,a rough sets based global reduction approach,which is suitable for imaging spectrometer image is proposed.According to the fuzzy sets and rough sets theory,the set of original bands is first automatically divided into several approximative equivalent intervals. In each interval, equivalent bands are linearly combined into one by using genetic algorithm under the consideration of the combined images of other equivalent intervals.Experimental results indicate that the global reduction approach is not only relative faster, but also better than independent reduction approaches.Taking the global reduction as the preprocessing step of imaging spectrometer images, we can apply traditional remote sensing image classification approaches to this type of remote sensing image data.
Since synthetic aperture radar (SAR) is a coherent system, images acquired by SAR are accompanied with speckle noise which disturbs image interpretation and target classification. This noise is conspicuous in single-look SAR images. Based on the analysis of the local speclke statistics characteristics of single-look SAR image and algorithms of spatial filtering,an adaptive speckle filtering method is presented in this paper. The Kuan filter which is based on MMSE criterion is modefied in the method. One of the focal points of the algorithm is to find the set of pixels which belong to the same homogeneous area within filtering windows adaptively. The local relative standard deviation within filtering windows is und as the crucial parameter while a special neighborhood model is used in the filtering window in order to choose the largest homogeneous area within filtering windows. Firstly the formal relative standard deviation Cx of filtering window is calculated.Then the filtering window is divided into eight mutually exclusive sub-window and the central pixel is the only repetitious pixel in each sub-window. For every sub-window, the local relative standard deviation Ci is calculated. If Cx is large than a threshold Cu,the sub-window with the greatest Ci is removed from filtering window and Cx of remaining pixels in filtering window is recalculated. Repeat the procedure until Cx<Cu. The remaining sub-window are meed as filtering area. The selected filtering area is the largest homogeneous area in filtering window and the Kuan filtering algorithm is adopted within the filtering area. If all sub-window within filtering window are removed, reduce the size of window for the determination of homogeneous area. If the size of window is 3 by 3 pixels, replace the central pixel with the average of the nearest four pixels around it. The method is applied to several single-look ER-1/2 SAR images. The results show that the performance of the approach presented is satisfactory in both speckle filtering and the Preservation of image details, and in generating visually-natural images as well.
GIS is widely used in many fields. With the rapid development of computer network,GIS users care more about data sharing. In traditional database, data consistency was controlled by consistency control mechartism. When a data object is looked in a sharing mode,other transactions can only read it, but can't update it. This is appropriate in traditional databases which store at tribute data and mainly deal with short transactions. In spatial databases, because of a large amount of data and complex topological relations, long transactions are used frequently. If the tra ditional consistency control method has already been used, the system's concurrency will be badly influenced. So there come many new requirements about the consistency control in the field of GIS.In this paper, data consistency is discussed in multi-user geographical information system.When a user updates some spatial data that have been accessed by other users in database,or exe cutes a UNDO/REDP operation, data consistency probably be destroyed. To solve the problem caused by the first case, a "notification-reread method"is introduced. As for the second case, there are many problems to be studied.
Based on analyzing characteristics of distributed geography information, and summing up different construction methods of Internet CIS such as CGI, Plug-in,ActiveX,Java and so on,the paper presents the requirement of Internet GIS to meet access and processing of DGI(distributed geography information). There are distributation, interoperability and componentization. Completely different from traditional GIS software data model, the communication between Browser and Server has to be taken into account in Internet GIS. Generally, it is the basic characteristic of Internet GIS to access data from a machine and process data in another one. This paper tries to solve the problems as follows:①How to send mp to Server and get response to Client-side; ②What is the appropriate spatial data structure of sending and receiving data for both sides;③How to process multi-request from Clients. Accessing to Browser/multi-Server architecture-based Internet GIS,and combining with the concept of component,the paper defines spatial data structure to access and response spatial data to communication between Browser-side and multi-Server-side. The data structure is fit for distributed data access and management after project application. By the construction method, the problem of distributed geography information querying and accessing spatial data may be solved. Finally,an application, which is based on Inter-net GIS-GeoSurf acts as an example to explain ideas as above.
The rapid advance of middleware technology is one of the most important characteristics in software development in recent year. This paper introduces the application of middleware technology, the software and design of the Nanhai land administration information system (NHLAIS).CORBA and DCOM provide complete and effective mechanism for the application, combination and management of software from different platforms. These series of technological break through bring out the combinization of software application and the componentization of software production. By combing the different software from different places effectively, the combinization resolves the application problem. The software system is decomposed into several independent components by the componentization technology of software production. Through standard system,,environment such as ActiveX and OpenDoc, these GIS components can realize the system combination effectively by connecting with other non-GIS components. The middleware refers to the software Shielding the difference between the operation system and netware protocol, providing the communication service among the system of different architectures. The Client/Server mode of three tiers based on middleware divide the application logic into three parts. Indication logic (Client tier)——the first tier, realizes the friendly interaction between the user and system,transfers the coral service the operation logic, displays the operation result. Operation Logic (Server component)——the middle tier, realizes the coral operation logic, manages and receives service request from the Clients, transfers data operation to resource manager, returns the operation result to the applicants——Client or other Server. The management of data of application system is executed in the data manager the third tier. In general the middleware has the following categories:remote procedure call(RPC), message-oriented middleware(MOM), object request brokers(ORB), database access(DA), and distributes transaction processing(DTP).NHLAIS is a wild area network (WAN) system. The center of the network is located in the Nanhai City Land Bureau. The 20 town sub-bureaus serve as the node of the network. Inside the City hand Bureaus a 100MB local area network (LAN) based on TCP/IP adapting Windows NT server and Windows 98. A proxy server communicates with the ISP through optical fibre. The application program in the workstations of the town sub-bureaus communicates with the ISP through the dialing mode. The non-spatial data is managed by SQL Server 6.5 from Microsoft.The SDE for SQL Server from ERSI manages the majority of the spatial data. With SDE the speed of loading map is enhanced. The cleaveless space database is established. The burden of the network is lowered. In NHLAIS, the Active Report of microsoft is adapted for the report output.MO from ESRI is adapted for the communication with different categories of map.
As we know,global positioning system (GPS) can be used to get precise relative position in a three-dimensional system. The results of many field-tests and applied projects have already shown that, GPS survey method can take the place of classical horizontal terrain survey method. But how to interpolate the abnormal height of GPS leveling, so as to take the place of classical leveling survey method, has attracted many geodesists in the past ten years. Up to now, a lot of methods have been discussed and applied.According to the development of GPS height abnormal height interpolation system (GANHIS),this paper discusses some mathematical models and the key techniques of GPS leveling.Firstly, the general design of GANHIS is illustrated with DFD (data flow diagram). Secondly, the mathematical models of GANHIS, including the polynomial curve interpolation method, the three-spline curve interpolation method, the curve interpolation of Akima method, the polynomial curved surface interpolation method, the multidimensional function curved surface interpolation method,the motion curved surface interpolation method, etc. are presented in brief. The characteristics of each method are offered as the mathematical expression.In succession, the key techniques of implemention GANHIS are stated briefly:1) To adopt the rotation of coordinates to ensure the precision of curve interpolation methods;2) To adopt the correction of terrain to ensure the precision of curved surface interpolation methods in mountainous areas, and its calculation, method is provided;3) To adopt the reliability testing of GPS bench marks to exclude blunders;4) The method of assessing precision is provided;5) The method of protracting the isoline of GPS normal height is introduced.GANHIS has come int use since 1998. In this paper, an application example is given, and it is proved that the result is good:both the internal precision and the outside precision are superior to the limit error of IV-order leveling. Finally, some significant conclusions are drawn:①For localGPS net, if the design of GPS net is reasonable, we can achieve IV-order leveling precision with GPS leveling method. ②GANHIS provides lots of interpolation models, so we can verify the interpolation result with different methods. The example in the paper proves that the precision of the polynomial curved surface interpolation method is approximate to that of the motion curved surface interpolation method. ③GANHIS has not only prominent economic benefit, but also important application and popularization value.
Based on the characteristic of the perfect spatial distribution of the T/P altimeter data,a spatial analysis method is performed, which transfers the constituents harmonic constant H and into a pair of orthogonal parameters U and V, and then expresses each of them with a polynomial function.As Parameters, the polynomial coefficients are derived with altimeter data on the least squares criteria. Thus the models of the main tidal wave in South China Sea are established.72 wees of TOPEX/POSEIDON data through weeks 11 to 82 are included in the calculation.The models are evaluated with different approaches and data set. The conclusion is that the tide models can provide partial tide amplitudes with 3cm accuracy, phase lags deviation of those amplitudes which are large over 10 cm are within ±10°, and the tide models derived are better than those of Schwiderski and SR95.1.
In order to resolve the normal. height of GPS nets in mountainous area, a new geometric method considering terrain effect is discussed in this paper. The mathematical model of the new method is also given. Besides, the accuracy of this method using non-grid height's data is also analyzed. The effect of using non-grid data and interpolation method on calculating normal height is estimated. In order to improve interpolation accuracy in the area where terrain changes very greatly, topographic map of GPS net is advised to use for practical application. Of course, net shape and number of GPS leveling points should also be considered in practical calculation. If the condition can't meet in practical wok, the correspond measurements are given in the paper. Using the new method,a few of GPS nets in mountainous area have been tested in the paper. The result shows that the accuracy of this method in mountainous area approximates as high as in smooth area. All these show that height determination with GPS leveling data considering non-grid data and effect of terrain valid in mountainous area.
Former dynamical equations of Chandler wobble did not introduce damping attenuation index. Therefore, it says that Q of Chandler wobble can not be easily specified directly from polar motion data. A resonance excitation model is introduced, which provides the reason that CW amplitude reserves an adequate level. And later, the resonance excitation model is developed into a parameter resonance one. The parameter resonance model shows that CW amplitude oscillates high in long period. In this paper, Q of Chandler wobble is easily specified from IERS polar motion data using the developed resonance excitation model. But since in resonance excitation model the damping index is linear, Q of Chandler wobble specified from the data shows a little small.Then frequency modulation is introduced. The frequency and damping parameter in the resonance excitation equation become as time-dependent parameters. Parameter resonance model can provide a revision of visco-elasticity for computing Q. Then the mean value of Q is 63, which is increasing slowly at the rate of 0.8 every secular period. This result is very much identical with the theoretical Q result of 69 under visco-elastic PREM model. It shows that parameter resonance model is exactly appropriate with the visco-elastic theoretical model. The long time tendency of Chandler wobble is figured out. Frequency modulation can be seen and analyzed spectrally. Time series of attenuation index is provided and time series of Q shows a very stable result in the figure.
This paper demonstrates that cartographic symbol system belongs to Boolean algebraic one according to Boolean algebraic definitions and sufficient conditions. The graded principle of cartographic symbol system and its constituted methods are expressed by defining the relation of equal value in cartographic symbol system. The theoretical value and practical meaning of structure map contents by multi-level algebraic operation in computer-aided cartographic are researched. Because Boolean algebra is a system suitable for logic operation of computer, it provides wide prospects for the exploitation and application of the software of computer-aided cartography.
The 110 emergency alerting station has been available in most part of China, and its rapid reaction has a deep impression on the people. Therefore, the people are willing to solve problems via 110 emergency alerting station. The 110-linkage system provides a single interface to the citizens and is linked with relevant entities with a view to deal with some emergent business.Wuhan power supply bureau maintenance management system linked with 110 emergency alerting station is a distributed process system combining with telephone reception, telephone recording,voice compression, voice synthesis, database management, and network communications. Wuhan power supply bureau business process center can transfer the users complaints to the suboffice via network. When the business is dealt, the process information will feedback to the business process center. This system provides the transfer process of maintenance forms process via network using multimedia audio technology. The whole system has implemented automatic data process of com-plaints reception, maintenance forms down-transfer, maintenance forms transfer management, assignment check, information search, telephone recording check and listening, audio transfer on net-work,failure information achieving, statistics, etc. The system has an important influence on the standard management of electrical system, and the improvement of service quality and work efficiency. We have a definite objective in the whole system design, that is, adopt the practical, reliable, existing and mature technologies under the prerequisite of fulfilling the system requirements.The historical experience has shown that this approach shall shorten the system development time, improve the system reliability, and at the same time meet the practical needs.
For a long period the computer networks consist of various kinds of computers or various kinds of networks. It is very important that how to solve the problem of internetworking on heterogeneous networks, and real-time communication between computers is also a hotspot in net-work applications. In this paper, an idea of "homogeneous translation of heterogeneous networks"is advanced, the implementation method of real-time communication is discussed, and the model and scheme to solve the problems are also provided.The "homogeneous translation of heterogeneous networks"can be divided into two idea layers. The first is called"homogeneous translation on network layer"and the second is called "homogeneous translation on interface layer".The realization of homogeneous translation on network layer is to use TCP/IP protocols. Be-cause most operation systems now support TCP/IP protocols,so if the programs are based on different systems which use TCP/IP protocols, at the view of programmer, all the networks are TCP/IP networks. On the other hand, our final objective is to communicate between applications,and the application access TCP/IP must go via socket.The sockets of different systems are distinct, so the "homogeneous translation on interface layer"is to solve the problem.The idea of "homogeneous translation of heterogeneous networks" mentioned above, greatly predigests the design and implementation of the communication on heterogeneous networks. This paper provides a path to resolve the problems.Real-time communications need transfer a mass of high-speed data between computers through networks. High-speed and real-time are the characters. That is said the transfer speed is high and the delay is dinky. In general, the speed lies on the hardware, but the real-time is related to the transfer mode. The implementation method which is discussed in this paper can be reduced to three processes.1) Internetworking with TCP/IPThe key of Internetworking with TCP/IP is to load TCP/IP protocols in various systems.Because programmer directly accesses network operation system, so they can avoid the hardware of networks. To load protocols in different system, the way is different, but the core is to provide a protocol stack. It is very easy to install and configure TCP/IP in Windows 95/98/NT. The steps are:open control panel, double click NETWORK icon, add Microsoft's TCP/IP protocol, then in the property dialog, input the IP address and subnet Mask, restart the computer.2)Use Berkeley socket as development interface Although the socket standard in different systems is various, but they have a intersection.That is the Berkeley socket. It is to say, all the socket standards support Berkeley socket. In spite of the difference in internal mechanism of socket, what is provided to programmer is a series system function call. Some important ones are as follows:(1)Create socket-socket()(2)Specify local address-bind()(3)Establish socket connection-connect () accept ()(4) Listen connection request-listen()(5)Send date-write(), writev(), send()/Sendto(), sendmsg()(6)Receive date-read(), readv(), recv()/recvfrom(), recvnsg()3) Use Client/Server modelThe experienced method to realize real-time communication is to use the end-to-end mode. To establish a end-to-end mode communication, the Client-Server model can be employed. Because the kernel of Client/Server model is that two processes in network must have a "handshake"course before transfer data, one requests and the other responses. When the "handshake" course is successful, a virtual circuitry is established between the quits layer from communication-source to communication-terminal, then the data transfer is on the circuitry, the middle mode exist or can not be ignored.
This paper presents a monitoring and controlling system which integrates single chip computer with linear CCD image sensor used for on-line industry. There are fine parts in the hardware setup. They are optical system machinery, linear CCD image sensor and its driving circuit, binarilizing circuit and 8098 user setup. The control software has functions such as displaying and managing keyboard, receiving and storing data, calculating and managing data, correcting deviation and sending out control signal. The measuring range is adjustable because the method of single chip CCD and single end measurement is used. The method of minimum bi-multiplication is applied in the software to correct system deviation. Experiment has proved that the system is practicable.