2007 Vol. 32, No. 11
Considering the rapid development of space and information technology,Chinese national height control network,as one of the backbones of geographical spatial fundamental infrastructures,is necessary to be updated and modernized.There are two tasks for the modernization of Chinese national height control network,the first one is to update the national 1st order leveling network.To lay down a national 3rd term 1st order leveling network in the near future is according to the "Law of Surveying & Mapping of the Peoples Republic of China",which defines that "national base surveying & mapping results should be updated in certain term and base surveying & mapping results urgently needed by national economy,defense construction and social development should be updated in time." It is the guarantee to keep the Chinese vertical datum and normal height system updated and reliable.The second task is to refine the Chinese quasi-geoid to cm magnitude accuracy and 5′×5′resolution.The "GPS + geoid" technique can be used to obtain altitude with cm accuracy at any place in Chinese mainland easily and quickly.Then the modern Chinese national height control network will be a reliable and suitable height frame in the geographical spatial fundamental reference frame for China before the year of 2020.
With the development of the theory and observation techonlogy on gravity field modeling,3D visualization has become a useful tool to analyze the changements and characters of the graviy field models in series.3D visualization of gravity field models based on the data mining method is an innovative research direcion.In this contribution,pivotal technologies of the 3D visualization of gravity field models using data mining method are discussed,and a corresponding 3D visualization system,WHU-3Dgravity is designed and developed.
The idea and concept of the seamless stereo orthoimage database in a continuous block area is put forward.The principle and implementation of stereo orthoimage database are presented.Based on stereovision of human's eyes,the main idea of seamless stereo orthoimage database is to generate a seamless digital orthophoto quadrangles(DOQ) database from DEM and odd photos and generate additionally a digital stereo orthophoto partner(DSP) from DEM and even photos,and a large area 3D virtual landscape environment can be formed without y-parallax.The database is called seamless stereo orthoimage database formed by DOQ and DSP together.In such environment,the 3D measurement and analysis can be done under the interface of normal GIS or CAD systems without complex DPW.The 3D objects,such as houses,trees,cloverleaf junctions,geologic ruptures,and so on,which are not acquired during data acquisition at DPW,can be measured by end user himself.The case study and some potential applications are given at last
The advances in research of GNSS-R,including the key areas,such as altimetry,sea wind,soil moisture remote sensing and space-borne experiment,etc,are reviewed,the key technologies of the GNSS-R software receiver and the retrieving model are analyzed.And the problems and development direction are pointed out.
The relevant theory and methods for studying regional crustal deformation with application of GPS technology are reviewed,the modern developments in this field is discussed.The strain analysis with least squares collocation method for displacements and inversion method of negative dislocation model are mainly introduced.The advanced spatial-temporal analysis methods for extraction of crustal deformation signals from space geodetic measurements are prospected.
Renew and maintain of the geodetic coordinate system need not only the continuous monitoring or repeated measuring,but also the reasonable data processing principle and method.The influences of different adjustment methods,including classical adjustment,sequential adjustment and adaptive sequential adjustment,on the datum or the coordinate system are analyzed,a GPS monitoring network is employed to analyze the datum changes due to applying the different adjustment principles.It is shown that sequential adjustment will distort the datum when some of the prior positions have significant deformation.The adaptive sequential adjustment,however,controls the influences of the outliers existing the prior coordinates,thus keeps the datum reliable and reflecting the present position.
Linear model in surveying adjustment is analyzed,four kinds of basic linear model and their generalized matrix reverse solution are presented;many linear model may induce and take into the adjustment model which considers and eliminates or weakens the model errors are pointed out.A simple solution is proposed.Some suggestions about linear model applied studying are put forward.
A new approach named the mirror surface projection method is proposed,may be utilized to determinate the orbit of a GEO satellite precisely.It sets the orbital plane of the GEO satellite as the symmetry plane(or the mirror surface),the original observation stations as the virtual observation stations by projection;the distances from the original stations to the GEO satellite are used to constitute the virtual observation values.The simulating computations indicate that the effect of the new method obviously excel that of the existing method in the precision of the orbit determination.
The scientific significance,function and application of geoid in geodesy and related geoscience are elaborated.The conception of combining GPS with high precision geoid to replace leveling in China is brought forward.The prerequisites of long wave,medium wave and short wave of Earth's gravity field to compute geoid with cm-level accuracy are analyzed.Some crucial techniques,necessity and feasibility of determining city geoid with 1 cm and provincial geiod with 5 cm are discussed.The main theoretical problems and mainly crucial techniques to be solved in cm-level geoid determination in China are presented as well.And the main progress and achievement of regional geoid determination in China are reviewed.
In order to eliminate the inconsistency of the existing data from multi-satellite missions,a new method is proposed for optimal combination of the altimeter data.In the data management system,the crossover adjustment is modified to a two-step processing based on the posteriori compensation theory of error,i.e.the crossover adjustment of condition equations is made in the first step,and the filtering and prediction of adjustment corrections done along each single pass in the second step.Using the new approach can simplify the solution procedure of crossover adjustment greatly,and the stability and reliability of its computation results can be expected.The new method can be used to both local and global crossover adjustment problem.Finally,practical altimeter data set from Geosat,ERS-1,ERS-2 and T/P is used as a case study to prove the efficiency of the integrated data processing method.
The historical context of the H-Cell concept is examined,and the current workflow is used in China.A set of hydrographic procedures will be designed to replace the traditional hydrographic deliverable with the bathymetric H-Cell and the photogrammetric H-Cell.One such initiative is the H-Cell.The H-Cell is used to not only update the DNC in a timely manner,but also produce multiple products.
The chaos theory is applied to optimize "Tuned" masks,which makes use of the randomicity of Logistic equation describing chaos phenomena,in instead of the randomicity of the randomizer based on a uniform distribution.And the corresponding "Tuned" masks are used in the texture classification of aerial image.The experiments show that the new approach can improve the classification accuracy of aerial images,which is promising in the application.
Three kinds of operational methodologies and their mathematic models of modern aerial photogrammetric point determination are described.A combined bundle block adjustment system WuCAPS,which can make conventional bundle block adjustment,GPS-supported bundle block adjustment and POS-supported bundle block adjustment,is developed based on the basic mathematic models mentioned above.Real aerial photographs,at image scales from 1∶2 500 to 1∶60 000,with POS data taken over various topographies in China were processed by WuCAPS.The accuracies of photogrammetric point determination from three methodologies are compared and analyzed.The empirical results have verified that the coordinate accuracies of the photogrammetric points can meet the requirements of the specifications of topographic mapping.However,it is necessary for topographic mapping to adopt the most economical and the most operational methodology.
The status of remote sensing technologies is underdevelopment.There are lack of the theories and methodologies for the processing and analysis of remote sensed images,and still no system of the theories and methodologies set to fit with the characters of remote sensing images.Therefore the system of theories and methodologies for the processing and analysis of remote sensed images based on the image segments is proposed to be set up.The concept and approaches of the texture analysis for multi-spectral /hyper-spectral images,the spatial relation analysis based on the image segments,the methods for taking the priori knowledge into the process of analysis and the researches for the techniques of data conflation have been discussed as well.
For extracting ground points from LIDAR points clouds quickly and generating high accurate DTMs effectively,a filtering method based on multi-resolution directional prediction is proposed.The method works by constructing multi-resolution datasets,smoothing datasets from low to high resolution based on directional prediction,and comparing the original LIDAR points clouds with the smoothed dataset to get bare ground points.The method improves the algorithm of "Inverse Distance to a Power" based on fixing its deficiencies in interpolating ground points.Highly accurate DTMs are interpolated by the proposed algorithm using bare ground points.It is confirmed that the algorithm is efficient in removing non-terrain objects and preserving terrain features,and holds promising potential for applications.
The former Soviet Union scholar Borodin(Бородин) has suggested a map object selection principle which can consider the object importance(e.g.the river length) and the density of object distribution(e.g.the distance between the adjacent rivers) simultaneously.But no concrete algorithm for implementation has been given by Borodin.Scholar of China,Zhu Guorui has suggested an excellent method for implementing the Borodin's principle and named this method as Method of Geometric Sequences.The main intentions of this study is to state the mathematic foundation of creating the density control table of map object selection,to found the essence of Difference Geometric Sequences of Borodin's principle,to generate a more simpler algorithm and to discover some intrinsic laws of structure of matrix elements.
Geo-spatial data updating based on map generalization is one of the important ways for GIS data updating.This study is focused on the approach for road data updating based on map generalization.The selection method for road data based on mesh density and road matching method considering the levels analyses is proposed for this procedure.This approach is applied in the project of national GIS data updating at 1∶50 000 scale,and the results shows its feasibility.
Faced to the challenges and difficulties of constructing distributed virtual geographic environment(DVGE),the approach for building DVGE based on Peer-to-Peer(P2P) network is put forward,which are resulted from the analyzing of the current structure of DVGE and the adaptability of the existed P2P network.For the method,the key problem is that how to design the logical model and topology structure for P2P network conformed to the service of DVGE.Therefore,the four-tier P2P logical model for DVGE system are presented,and for supporting the functions of this P2P logical model,the topology structure of the P2P routing model named spatial related hierarchical circinal routing model is designed.The test DVGE system,which has simulated its communication performance between the peers in the network,is also presented,and the prospective performance is gotten.
The latest research activities is summarized and outcomes of GIS for Transportation(GIS-T) data modelling following the associated concepts of GIS-T are presented.An integrated spatio-temporal framework for GIS-T data modeling is proposed,which fits well for modeling of dynamic traffic information and road network data.Before
The estimation and management of the response time is an important problem of spatial information service.Aiming at the automatic generation of spatial information service chains,the determinate model and the probability model for response time estimation is established,and the concepts of critical path,critical service and service slack are defined.In order to ensure the response time of services chains satisfy the requirement of users,an optimal service composition algorithm based on critical path method is proposed to select appropriate component services.Experimental results show that this algorithm optimizes the response time of spatial information service chains.
The mode to integrate outdoor augmented reality with mobile GIS is investigated,a general framework of outdoor augmented reality GIS(OARGIS) is designed.Several key technologies for OARGIS implementation are researched with emphasis and based on which a prototype system is implemented.
The research works and the existing problems of spatial analysis based on analyzing development of spatial analysis theory and techniques are summarized.Key technique problems from spatial analysis to spatial decision making transit which are necessary to be solved have been pointed out.The considerations for future development of spatial decision making are presented.
A new watermarking algorithm is presented based on multi-scale error diffusion,it hides information in the low dot percentage area,which has better data recovery performance than the area of high dot percentage.This technique enhances the performance of watermark extraction,and provides a new choice for the application of digital watermark in printed images.