2006 Vol. 31, No. 10
The accuracy of direct georeferencing by airborne position and orientation system(POS) in WGS 84 coordinate system and in 80 Xi'an geodetic coordinate system is appraised,the height accuracy by using different geoid simulate methods is analyzed,the boresight angle errors of POS system are calibrated and the calibration results in different test fields are discussed.The empirical results have verified that direct georeferencing of aerial photogrammetry based on POS system requires a calibration field with at least 1 XYZ ground control point to eliminate system errors.The accuracy of direct georeferencing is very good in WGS 84 coordinate system.However,it is necessary for getting accurate 3D coordinates of the photogrammetric points to correct height by using geoid simulate in 80' geodetic coordinate system.
The water quality monitoring of Huangpu River upper stream is studied based on remote sensing and GPS technologies.The processing methods of multi-spectral remote sensing imagery are presented,and the inversion models of the typical water quality parameters Dissolved Oxengen and Secchi Disk are derived.The results show that remote sensing is a fast and feasible water quality monitoring method,and can detect effectively the temporal and spatial distribution of water quality.
An algorithm within framework of wavelet analysis based on the statistic characteristics of wavelet coefficients is proposed.The wavelet decomposition of logarithmically transformed SAR images is accurately modeled by stable distributions.The result of experiment indicates that the proposed method reduces speckle in SAR images while preserving the structural feature and textural information of the scene.
The local correlation coefficient is introduced and the different thresholds at different levels of wavelet decomposition are set up, in order to reduce the spectral distortions of the fusion image,fuse multi-spectral images with a panchromatic image of Quickbird data by the proposed method.The result demonstrates that the proposed method is a good fusion method to increase information,improve resolution and reduce spectral distortions.
A brief review of InSAR atmospheric correction approaches,which have been developed to reduce atmospheric effects(particularly water vapour effects) from SAR interferograms in the last decade,is given.Emphasis is given to GPS topography-dependent turbulence model(GTTM) developed at University College London.Examples over the Los Angeles region reveals that,without InSAR atmospheric correction,the RMS differences between GPS-derived and InSAR-derived range changes in the line of sight(LOS) direction were 1.0 cm.After applying the GTTM,the RMS differences decreased to 0.5 cm,suggesting that the GTTM successfully reduced atmospheric water vapour effects on interferograms.A comparison between the GTTM and the GPS/MODIS integrated water vapour correction model shows that the GTTM and GPS/MODIS integrated models are complementary when correcting InSAR measurements.
An elevations selection approach of area target surveillance task using multi-satellites is presented.The approach includes two stages: pretreatment and optimization.In the pretreatment stage,STK is applied to solve the difficult problem of computing access time;in the optimization stage,models and solving method based on genetic algorithm is presented,and a scenario instance proves the validity of the method.
In the integrated navigation system of GPS/SINS,the heading's observability is very weak,although the heading error is improved after Kalman filter,the trend of heading is divergent and is even larger when the SINS of low cost and low precision is introduced.In order to eliminate this divergent trend,the method that AHRS revises the heading of SINS on-line is put forward.The practical static and dynamic experiments illustrate that this method can effectively eliminate the divergent trend of heading,the positioning precision is very high,which provides theoretic basis for the abroad application of GPS/SINS system.
The meaning to research the potential of space VLBI for geodetic applications is summarized.The observation types of space VLBI are investigated,and so are the observation models and their related parameters of geodetic interest.With the world wide VLBI data from 1980~2004,the conditions to compute the parameters of geodetic interest are introduced,and so are the computing methods and processes.And the computed results of the parameters of geodetic interest are analyzed.
The precision orbit determination of CHAMP satellite was done through PANDA(position and navigation data analyze) software,using the onboard GPS data from day 126 to 131 of year 2002.The orbit accuracy is assessed by analyzing the difference from GFZ precision orbits,the data residuals and the satellite laser ranging(SLR) residuals.The comparison results show that the accuracy of the orbits obtained is 4-5 cm in radial and 6-8 cm along and across the track.
The cross-coupling corrections for the LaCoste&Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors,the weight factors(coefficients) determined from marine gravity data by factory are obviously not be optimal for airborne application.These coefficients are recalibrated to minimize the difference between airborne data and upward continued surface data(external calibration) and to minimize the errors at line crossings(internal calibration) respectively.An integrating method to simultaneously recalibrate the above-mentioned coefficients and the beam scale factor is also presented.Numerical results show that the systemic errors in the airborne gravity anomalies can be greatly reduced using any of the recalibrated coefficients.For example,the systemic error is reduced from 4.8 mGal to 1.8 mGal in Datong test.
An overview of the immune algorithm is offered,and the main principiums and the characteristics of immune algorithm based on clone selection principle are discussed.The applications of immune algorithm in survey data processing by two examples are analyzed.The results show that immune algorithm can settle the problems of survey data processing.
As a main factor of fractal geometry,fractal dimension is used to quantificationally analyze the spatial complexity of map objects.But it is proved in practice that a map object(usually) shows nonuniformity of local fractal character.A meta fractal dimension model is put forward based on fractal theory that can be applied to describe the change of local shape of objects,and a new method for their further applications and analyses is offered.
Two schemes for data integrated process and partition adjustment calculation according to section are provided.All kinds of equations of data process methods about the partition adjustment calculation are discussed in detail.The data process methods are proved to be reasonable and practical by the map data instance.
A method is introduced that begins with the confirmation of the projection boundaries.The projection theory is described systematically and the strict transform formulas are given step by step,and forward and inverse algorithms of SEA projection are designed.
The theory of the optimum query of public transportation based on the least transfers is put forward,and the algorithm to realize it is designed.The graph algorithm is tried to realize based on the spatial network database,making use of the quick query,index support and the collection operation of database to acquire excellent efficiency,and making use of spatial query support of such type of database to ensure that the algorithm can get the shortest path after getting the least transfers.
A data compress idea is put forward by considering the judge accordance of the angle between two normal lines of the triangular plane face.So that the corresponding algorithm of the data compress is given by calculating the angle between two normal lines.The acceptance or rejection of a point is determined according to the comparison between the biggest angle with the defined threshold.As a case study,the Kongzi portrait in Tongji University is scanned and the real three dimensional model is established.The data compression aim to the Kongzi portrait is conducted to achieve the realization of the given method.In order to prove the feasibility of the method and the quality of the compression,several evaluation results are then analyzed same with the case data.
A new reuse method in the specific domain is proposed.The conceptions,the attributes,and the way of development about datalization are studied,and a meta model is constructed.For the variability factors are expressed in datum,the stability and capability of reuse of domain software are strengthened.Take OfficeGIS as example and proves that this approach will be beneficial to software reuse practices.
A spatial data mining prototype system(visual geo-classify) based on VC~(++) 6.0 and MapObject2.0 are designed and developed,the basic arithmetic of the spatial data mining of the system is used decision tree and Bayesian networks,and datum classify are used training and learning and the integration of the two to realize.The result indicates that this prototype system is a practical and extensible visual interactive spatial data mining tool.
According to the characteristic and contents of 3D geospatial information application field,a 3D geospatial information application grid architecture is proposed,the concrete application and the key techniques of 3D geospatial information are discussed around above grid architecture.And the prototype system(GridVRMap) of 3D geospatial information application grid is set up.
The idea that use the structure of semantic meaning query tree as middle language is put forward.The algorithm of translation Chinese query sentence of GIS into semantic meaning query tree is designed.In order to solve the difficulty of nested structure of SQL,the idea of query block is introduced and the algorithm of changing query block to SQL is realized.The compare of this way with old ones has been done.The experiment shows that the validity has been enhanced.So it is a better way to understand Chinese query sentence.
The fundamental principle of a novel vector graphics visualization method named JVGL is introduced.The concrete approach of applying JVGL to Web GIS platform from these follow aspects: unifying the map window with JVGL,visualization of map symbols(using) JVGL,the JVGL-extended support to GML,etc.,are analyzed.The feasibility of JVGL method through a practical Web GIS site is testified.
An meta-component modal is established and an approach to composit GIS components oriented user's tasks is proposed based on their meta-component modal which not only describes semantic information of a GIS component,but also the synthetic information,finally a prototype is implemented.
A method for constructing spatial index over the native XML is proposed.It also includes the path-index and the value-index,which are the base of spatial index.A new query language is introduced as XML-GSQL, which is designed to suit native XML and characterized by features of both XML document and database.And an examples of this language is given to evaluate the total efficiency of spatial query.