2005 Vol. 30, No. 3
The airborne laser scanning altimetry data contains the 3D coordinates of the laser footprints and intensity of the return pulse. The amount of light that is returned from a target's surface is characterized by the reflection coefficient. For a diffusely reflecting target, the maximum value of reflection coefficient is 100%. For mirror-like or retro-reflecting targets, the theoretical value of reflectivity can exceed 100% by far. The reflection coefficient is, of course, also depending on the wavelength. For the specified airborne laser scanning altimetry, the intense of the reflectivity varies with the interacted material of the object surface. For materials with skinny or glossy surface, the reflectivity figure represents the maximum light return, with the sensor beam exactly perpendicular to the material surface. Airborne laser scanning altimetry data classification algorithm combined with the intensity of laser is studied in detail. The fusion of height data and intensity data can achieve good classification
Based on the multi-scale features of the balance, this paper presents a multi-scale measurement for the dynamic balance between cultivated land demands & supplies and gives some detailed discussion on the basic models for the balance at the scales of total amount, per capita capacity, quality, time and space. Finally, this paper puts forward an adjust-control model to achieve the balance under the framework of land use planning.
Spatial scale is a fundamental problem in GIScience. The representative fraction of map scale is the traditional typical meanings. Also we use spatial extent and spatial resolution/granularity to represent geographic information and phenomena on paper or in digital environment. But all these are built on our cognition and the interpretation of space and scale. This paper illustrates the significance of research on spatial scale, then discusses the connotations and meanings of spatial scale in cognition, granularity, extent, map scale
This paper proposes the method of radial spatial division based on Q i(x i,y i) for realizing the restrained edges mosaic in constructed TIN. First of all, it introduces the basic principle of radial spatial division based on Q i(x i,y i). After that, on the basis of the principle the algorithm to realize restrained edges mosaic is given in detail. A spatial division tree is proposed as an efficient implementation method in the aspect of reconstruction of triangles and their spatial relationship after the division. The analysis of time complexity shows that the time complexity to execute Q i(x i,y i) is lower than that to compute the distance from a point to a line. It is shown that the radial spatial division algorithm proposed in this paper has more advantages in time efficiency than the spatial division algorithm based on distance.
Modeling spatial features in land and housing geographic information system (GIS) based on Geographic Markup Language (GML) is studied. The characteristics of the land and housing spatial features are analyzed, and the land and housing spatial features description based on GML is put forward. A schema defining the GML structure is given, in which both the geometry and attribute information of the features are incorporated, and the relationship between these features is described by the member model. The query models of the land and housing spatial features and the topology relationship between them are further presented, and a query algorithm is given based on XML and XQuery technology. An application system used to manage land and housing information is developed based on JAVA, DOM and SAX. The implementation of the proposed models is tested and the result proves the capability of the models and methods.
The objective of this paper is to discuss the efficiency storage of mass spatial data in grid GIS environments. This paper introduces a grid GIS data storage solution based on the integration of the advantages of grid and virtual SAN techniques. This solution is a milestone for the presence and future of GIS, aiming at seamless and high efficiency storage management and data service. Then this paper discusses the structure of experimental platform, the realization of the data service, and the advantage of this method.
This paper brief by introduces the interoperability and summarizes several main models of GIS interoperability. Then the interoperable GIS model——Open Virtual Model ( OVM) is given. OVM tries to resolve some problems in accessing distributed heterogeneous component databases transparently and operating the collaboration of GIS software function. An idea of common virtual interface is put forward. Based on the idea, the open and virtual OVM are analysed.
This paper proposes the concept, structure and principle of GIS intelligent agent (GIS-IA). GIS-IA is the basic unit that can realize GIS intelligent analysis, and the frame of intelligent analysis based on GIS-IAs is an effective way to realize intelligent spatial decision-making.
This paper designs service components of WebGIS by the research of inter-operability, open environment and spatial data transfer format based on XML. It is the first time to have realized the data conversion by using data decomposing and synthesizing. The experimental results show that customers can visit XML space data realized by this method.
This paper puts forward a system requirement meta-model to analyze system requirement. Based on the model, the method of system requirement analysis and the formal description method for describing the result of system requirement proposed are presented.
This paper studies the problem on extending the method for fitting between terrestrial gravity quasi-geoid and GPS leveling quasi-geoid to the case of sea area near coast. In theory, it is proved that marine geoid can not coincide with the corresponding quasi-geoid if sea surface topography (SST) exists, and a formula is derived for calculating the difference between marine geoid undulation and corresponding height anomaly. The formulas are presented to calculate the normal height of mean sea surface (MSS) on a local vertical datum and altimetric quasi-geoid. Considering the fact that altimetric MSS can have about the same accuracy level as that of GPS geodetic height, an extended method for fitting marine gravity quasi-geoid to altimetric quasi-geoid on a local vertical datum is advanced by using altimetric MSS data.
Ill-posed problem often appears in the inverse problem in geophysics. Many regularization methods are used to produce reasonable solutions. Among them, Tikhonov regularization and truncated SVD (Singular Value Decomposition) are two important methods used widely, but how to compare them is a challenging and meaningful area under discussion. The paper discusses the comparison between them. First, with the SVD of coefficients matrix, the ordinary least squares (LS) solu
This paper presents a method for robust estimation that corresponds to the adjustment of 2000 China gravity base net. It mainly adopts the theory of robust estimation, combined with the actual data of 2000 China gravity base net, compares and analyzes the data of 2000 China gravity base net through a great deal of computation.
An efficient static GPS measurement simulation of ground stations is studied in this paper, especially the significant, principle, flow chart and mathematical models used in GPS measurement simulation are analyzed. Then the simulation of GPS observation of Wuhan station is made. The results show that the GPS observations gained by the simulation method presented in this paper are very close to those observed. Therefore, the simulated GPS observations can meet various demands.
Carrier phase ambiguity solution for single frequency single epoch is the key to high precision for real-time kinematic positioning. An evolution algorithm-Genetic Algorithm was introduced to search GPS carrier phase integer ambiguities in single frequency single epoch. It is a new optimization method through simulating the process of nature evolution to search the best solution. An improved regularization method is applied to improve the accuracy of the float solution of the ambiguities. The improved float solution increases the success rate of fixing the carrier phase integer ambiguities, since not only the candidate integer set is reduced, but also the ambiguity float solution is improved. An example is illustrated to show the new method's effect. The result processed by Bernese GPS software using all GPS data in this example is taken as the standard of comparison. Then, some L 1 phase observations and C/A pseudo ranges are extracted, and each epoch's float solution is computed by the new regularization method. After obtaining more accurate ambiguity float solution, we could think ambiguity true value is around float solution for 3 circles. Under this precondition, Genetic Algorithm was used to search carrier phase integer ambiguity. The results indicated that the new method not only increased the success rate of fixing ambiguity, but also improved the search efficiency. Genetic Algorithm spent less time in searching integer ambiguity than that LAMBDA did. And Genetic algorithm was also proved a robust algorithm by some analyses using GPS data. The new research way based on the improving float solution will make great application significance to real-time kinematic positioning.
A method, based on reforming the “step edge” curve which clearly explains how the diffraction of sunlight makes digital aerial images blur, is proposed to deblur the texture extracted from digital aerial images and thus to improve its visual effect. First, histogram analysis and edge detection are integrated with each other to automatically find out the“step edge” curve for each line feature in texture. In this step, highly precise Canny algorithm is used to locate the central point of “step edge” curve and the two boundary points of “step edge” curve are determined by tracing the intensity histogram around located central point of “step edge” curve. As a result, “step edge” curve could be automatically precisely gained. After that, the selected “push” function anti-tangent is used to adjust the intensity of every the “step edge” curve and make it more steep around the located central point. Last, several textures extracted from digital aerial image are tested by the proposed strategy and algorithm, and the experimental result is encouraging.
This paper presents a spatial analysis method based on multi-temporal DEM elevation changes and DOM images changes and gives a qualitative and quantitative analysis of the terrain change. It has been applied in Mutuo of Tibet where the terrain and geological are very complex and the action of the earth's surface is active, and proved to be a quick, effective and precise method for analyzing the stability of the terrain.
This paper develops a new analysis method based on the hyper-multi spectral satellite data, which is the universal pattern decomposition method (UPDM). The results demonstrate that the mean square root values of reconstruct fitting errors are less than 0.029 when using it on Landsat/TM(ETM+),Terra/MODIS and ADEOS-II/GLI satellite sensors. The UPDM is especially suitable for hyper spectral satellite remote sensing data.
The basic theory and elements of the blooming melt of TSICO steel billet on-line measurement system is presented. The on-line non-contact measurement system adopts the infrared imaging technology. The program detects the steel billet's edge by computing the grads and searching the maximum grads, then subdivides the edge according to the grads. A new image processing technology is particularly presented ,which is applied to this non-contact measurement system. With the mathematic analysis and test result, the new image processing technology is demonstrated to be practical and robust.
This paper presents a novel approach of emitter recognition according to the idea of information fusion. In the new approach, D-S evidence theory is introduced during the processing of recognition using gray correlation analysis method. By redistributing the subordinate function of observation samples, this approach is effective in fusing the recognition results and improving the probability of accurate recognition. The simulation results show the feasibility and validity of the novel approach.