摘要:The validity measurement of fuzzy clustering is a key problem. If clustering is formed, it needs a kind of machine to verify its validity. To make mining more accountable, comprehensible and with a usable spatial pattern, it is necessary to first detect whether the data set has a clustered structure or not before clustering. This paper discusses a detection method for clustered patterns and a fuzzy clustering algorithm, and studies the validity function of the result produced by fuzzy clustering based on two aspects, which reflect the uncertainty of classification during fuzzy partition and spatial location features of spatial data, and proposes a new validity function of fuzzy clustering for spatial data. The experimental result indicates that the new validity function can accurately measure the validity of the results of fuzzy clustering. Especially, for the result of fuzzy clustering of spatial data, it is robust and its classification result is better when compared to other indices.
摘要:Given the second radial derivative Vrr(P)|σ S of the Earth's gravitational potential V(P) on the surface σS cor-responding to the satellite altitude,by using the fictitious compress recovery method,a fictitious regular harmonic field rrVrr(P)* and a fictitious second radial gradient field V*rr(P) in the domain outside an inner sphere Ki can be deter-mined,which coincides with the real field Vrr(P) in the domain outside the Earth.V*rr(P) could be further expressed as a uniformly convergent expansion series in the domain outside the inner sphere,because rrVrr(P)* could be expressed as a uniformly convergent spherical harmonic expansion series due to its regularity and harmony in that domain.In another aspect,the fictitious field V*(P) defined in the domain outside the inner sphere,which coincides with the real field V(P) in the domain outside the Earth,could be also expressed as a spherical harmonic expansion series.Then,the harmonic coefficients contained in the series expressing V*(P) can be determined,and consequently the real field V(P) is recovered.Prelimi-nary simulation calculations show that the second radial gradient field Vrr(P) could be recovered based only on the second radial derivative Vrr(P)|σ S given on the satellite boundary.Concerning the final recovery of the potential field V(P) based only on the boundary value Vrr(P)|σ S,the simulation tests are still in process.
摘要:Linear quadtree is a popular image representation method due to its convenient imaging procedure.However,the excessive emphasis on the symmetry of segmentation,I.e.Dividing repeatedly a square into four equal sub-squares,makes linear quadtree not an optimal representation.In this paper,a no-loss image representation,referred to as Overlapped Rec-tangle Image Representation (ORIR),is presented to support fast image operations such as Legendre moments computation.The ORIR doesn't importune the symmetry of segmentation,and it is capable of representing,by using an identical rectangle,the information of the pixels which are not even adjacent to each other in the sense of 4-neighbor and 8-neighbor.Hence,compared with the linear quadtree,the ORIR significantly reduces the number of rectangles required to represent an image.Based on the ORIR,an algorithm for exact Legendre moments computation is presented.The theoretical analysis and the experimental results show that the ORIR-based algorithm for exact Legendre moments computation is faster than the conven- tional exact algorithms.
摘要:This paper describes the operational issues and basic technical requirements of modern aerial photogrammetry.The accuracy of photogrammetric point determination and the y-parallax at corresponding model points is analyzed when stereo models are reconstituted by using the exterior orientation elements of aerial images.Real aerial photographs,at image scales from 1:2500 to 1:60000,with DGPS/IMU clara taken from various topographies in China were processed by our POS-supported bundle block adjustment program WuCAPS.The empirical results verified that the accuracy of the exteri ororientation elements from bundle block adjustment meets the requirements of the specifications of topographic mapping,However,the accuracy of the exterior orientation elements determined by POS fails to meet the requirements of the specifica-tions of topographicmapping.
摘要:To meet the requirements of efficient management and web publishing for marine remote sensing data,a spatial database engine,named MRSSDE,is designed independently.The logical model,physical model,and optimization method of MRSSDE are discussed in detail.Compared to the ArcSDE,which is the leading product of Spatial Database Engine,the MRSSDE proved to be more effective.
摘要:According to the different characteristics that signal and noise exhibit during wavelet decomposition,a new denoising method based on the lifting scheme wavelet packet decomposition is presented.In this method,the SAR images are decom-posed by using the best wavelet packet and the norm of each sub-band are calculated;signals and noise can be discriminated based on the norm and soft- threshold method,and the images can be denoised.Experiments show that the proposed algorithm has excellent performance in denoising SAR images,and can remove most noise of images with well-kept texture detail informa-tion.The calculating speed of the method is twice the speed of the general wavelet packet transform algorithm.
摘要:Geographic Information Systems (GIS) is being widely applied to official construction activities nowadays.This tech-nique can not only display graphs for each spatial data displayed,but also provide a broad prediction and decision tool.The pur-pose of this paper is to describe the capabilities of GIS application in building a new parking facility in the city of East Lansing through wide analysis of the surrounding data.The results are displayed in maps and graphs.Finally,the recommendation area is selected using three criteria:proximity to the downtown area;the degree of VACANT;and distance from all buffers.
摘要:Spatial clustering is widely used in many fields such as WSN (Wireless Sensor Networks),web clustering,remote sensing and so on for discovery groups and to identify interesting distributions in the underlying database.By discussing the relationships between the optimal clustering and the initial seeds,a clustering validity index and the principle of seeking ini-tial seeds were proposed,and on this principle we recommend an initial seed-seeking strategy:SSPG (Single-Shortest-Path Graph).With SSPG strategy used in clustering algorithms,we find that the result of clustering is optimized with more probabil-ity.At the end of the paper,according to the combinational theory of optimization,a method is proposed to obtain optimal reference k value of cluster number,and is proven to be efficient.
摘要:Based on research on information organization and visualization mechanism of multimedia electronic map,this paper proposes an organization method about spatial information and multimedia information of multimedia electronic map:seamless spatial data were organized and managed by stratified expansion R-tree and Quacl-tree hierarchy;and multimedia information data were organized and managed by hypermedia model based on an electronic map.Considering electronic map features,the paper also proposes a method for spatial date organization,which integrates Digital Landscape Model and Digi-tal Cartographic Model,and a hybrid model between vector and raster spatial data.Then,the paper studies information visu-alization mechanism of multimedia electronic map.Finally,the paper certifies the results via a case of multimedia electronic map authoring tools software-Atlas2005.
摘要:Human beings use hierarchies to simplify their conceptual models of reality and to perform reasoning more efficiently.Hierarchical structures are conceptually imposed on space and allow performance of complex tasks in very large con-texts easily.Hierarchical spatial reasoning is an important method for solving spatial problems.This paper briefly discusses the definition and frame of hierarchical spatial reasoning and its application to way-finding of road networks.
摘要:Due to the super rotation of the Earth's inner core,the tilted figure axis of the inner core would progress with re-spect to the mantle and thus cause the variation of the Earth's external gravity field.This paper improves the present model of the gravity field variation caused by the inner core super rotation.Under the assumption that the inner core is a stratifying ellipsoid whose density function is fitted out from PREM and the super rotation rate is 0.27~0.53°/yr,calculations show that the global temporal variations on the Earth's surface have a maximum value of about 0.79~1.54×103 μGal and a global av-erage intensity of about 0.45~0.89×103 μGal in the whole year of 2007,which is beyond the accuracy of the present gra-vimetry and even the super conducting gravimeter data.However,both the gravity variations at Beijing and Wuhan vary like sine variables with maximal variations around 0.33 μGal and 0.29 μGal,respectively,in one cycle.Thus,continuous gravity measurements for one or two decades might be able to detect the differential motion of the inner core.
摘要:On the basis of gravity field model (EIGEN_CG01C),together with multi-altimeter data,the improved deflection of the vertical gridded in 2'×2' in China marginal sea and gridded in 5'×5' in the global sea was determined by using the weighted method of along-track least squares,and the accuracy is better than 1.2" in China marginal sea.As for the qual-ity of the deflection of the vertical,it meets the challenge for the gravity field of high resolution and accuracy.It shows that,compared with the shipboard gravimetry in the sea,the accuracy of the gravity anomalies computed with the marine deflec-tion of the vertical by inverse Vening-Meinesz formula is 7.75 m·s-2.
摘要:There are various occasions where simple,ordinary,and universal kriging techniques may find themselves incapa-ble of performing spatial prediction directly or efficiently.One type of application concerns quantification of cumulative distri-bution function (CDF) or probability of occurrences of categorical variables over space.The other is related to optimal use of co-variation inherent to multiple regionalized variables as well as spatial correlation in spatial prediction.This paper extends geostatistics from the realm of kriging with uni-variate and continuous regionalized variables to the territory of indicator and multivariate kriging,where it is of ultimate importance to perform non-parametric estimation of probability distributions and spatial prediction based on co-regionalization and multiple data sources,respectively.
摘要:On the basis of simplification of the Planck function in a low temperature range,this paper revises the practical split-window algorithm and presents a method for retrieving snow surface temperature (Ts) based on MODIS data in the mid-dle-latitude region.The application of this method in Qinghai Lake region reveals that it is feasible for the retrieval of Ts.Re-sults of correlation analysis indicate that there was strong negative relationship between Ts and altitude.By analyzing three typical areas in which land cover was relatively homogenous,this paper discusses the relationship between Tsand normalized difference snow index (NDSI) and then presents a new concept named "NDSI-Ts space".
摘要:By using sonar imaging,this paper presents a new algorithm for the clustering of seabed types based on theself-organizing feature maps (SOFM) neural network.The theory as well as data processing is studied in detail.Some valuable conclusions and suggestions are given.
摘要:Qualitative spatial reasoning on topological relations can extract hidden spatial knowledge from qualitatively described topological information,which is of significant importance for decisionmaking and query optimization in spatial analysis.Qualitative reasoning on spatial topological information based on semantic knowledge and reasoning rules is an efficient means of reducing both the known relations and the corresponding rules,which can result in enhanced reasoning performance.This paper proposes a qualitative reasoning method for spatial topological relations based on the semantic description of reasoning rules and constraint set.Combined with knowledge from the Semantic Web,the proposed method can easily extract potential spatial results consistent with both unique and non-unique rules.The Constraint-Satisfactionbased approach,describing constraint set with semantic expressions,is then used together with an improved path consistency algorithm to veri~ the consistency of the unique-rules-based and non-unique-rules-based reasoning results.The verification can eliminate certain reasoning results to ensure the reliability of the final results.Thus,the task of qualitative spatial reasoning on topological relations is completed.
摘要:This paper presents a new framework for object-based classification of high-resolution hyperspectral data.This multi-step framework is based on multi-resolution segmentation (MRS)and Random Forest classifier (RFC) algorithms.The first step is to determine of weights of the input features while using the object-based approach with MRS to processing such images.Given the high number of input features,an automatic method is needed for estimation of this parameter.Moreover,we used the Variable Importance (Ⅵ),one of the outputs of the RFC,to determine the importance of each image band.Then,based on this parameter and other required parameters,the image is segmented into some homogenous regions.Finally,the RFC is carried out based on the characteristics of segments for converting them into meaningful objects.The proposed method,as well as,the conventional pixel-based RFC and Support Vector Machine (SVM) method was applied to three different hyperspectral data-sets with various spectral and spatial characteristics.These data were acquired by the HyMap,the Airborne Prism Experiment (APEX),and the Compact Airborne Spectrographic Imager (CASI) hyperspectral sensors.The experimental results show that the proposed method is more consistent for land cover mapping in various areas.The overall classification accuracy (OA),obtained by the proposed method was 95.48,86.57,and 84.29% for the HyMap,the APEX,and the CASI datasets,respectively.Moreover,this method showed better efficiency in comparison to the spectralbased classifications because the OAs of the proposed method was 5.67 and 3.75% higher than the conventional RFC and SVM classifiers,respectively.
摘要:Urban land density is an important factor to understand how cities expand.An "Inverse S-shape Rule"was implemented for the first time to analyze urban land density in Northeastern Thailand using the four cities Khon Kaen,Udon Thani,Nakhon Phanom,and Nong Khai as study sites.Land density function was tested using different data classification techniques from previous studies.Each city was investigated over two different time periods between 2002 and 2015.Declining pattern characteristics of metropolitan area density outward from city centers can be quantified by fitting the parameters to urban land density functions.An inverse S-shape function was identified as the best data fit.The four selected cities showed conventional density variation for decline in urban land area from city centers to outlying areas.Overall trend indicated that cities became more compact over time since the density differences between the urban core and urban fringe were greater with increasing infilling growth within the urban boundary.All four cities increased in size over time;however,the increasing amount of built-up land in the surrounding rural areas did not follow the same trend in each case.Some functional parameters required careful interpretation because of the linear shape of the city as in the case of Nakhon Phanom.Using highly detailed urban data resulted in lower densities of urban areas compared to the conventional pixel-based classification,and this affected the overall shape of the inverse S-shape function.The fitted parameters and their changing trends indicated that the urban land density function was useful for understanding urban form and urban sprawl in Thailand.Results can be used to develop a specific framework for other cities with similar attributes in the future.
摘要:Spatiotemporal data represent the real-world objects that move in geographic space over time.The enormous numbers of mobile sensors and location tracking devices continuously produce massive amounts of such data.This leads to the need for scalable spatiotemporal data management systems.Such systems shall be capable of representing spatiotemporal data in persistent storage and in memory.They shall also provide a range of query processing operators that may scale out in a cloud setting.Currently,very few researches have been conducted to meet this requirement.This paper proposes a Hadoop extension with a spatiotemporal algebra.The algebra consists of moving object types added as Hadoop native types,and operators on top of them.The Hadoop file system has been extended to support parameter passing for files that contain spatiotemporal data,and for operators that can be unary or binary.Both the types and operators are accessible for the MapReduce jobs.Such an extension allows users to write Hadoop programs that can perform spatiotemporal analysis.Certain queries may call more than one operator for different jobs and keep these operators running in parallel.This paper describes the design and implementation of this algebra,and evaluates it using a benchmark that is specific to moving object databases.
摘要:This paper presents a methodology and its software implementation for the performance evaluation of low-cost accelerometer and magnetometer sensors for use in geomatics applications.A known mathematical calibration model has been adopted.The method was completed with statistical methodologies for adjusting observations and has been extended to calculate accuracies for the attitude,heading,and tilt angles estimation that are of interest to geomatics applications.The evaluation method consists of two stages.First,the evaluation method reviews the total magnitude of acceleration or the strength of the magnetic field.Second,the evaluation is more detailed and concerns the determination of mathematical parameters that describe both accelerometer and magnetometer working model.A software tool that implements the evaluation model has been developed and is applied both in accelerometer and magnetometer measurement data-sets acquired from a low-cost sensor system.
摘要:Hydropower has made a significant contribution to the economic development of Vietnam,thus it is important to monitor the safety of hydropower dams for the good of the country and the people.In this paper,dam horizontal displacement is analyzed and then forecasted using three methods:the multi-regression model,the seasonal integrated auto-regressive moving average (SARIMA) model and the back-propagation neural network (BPNN) merging models.The monitoring data of the Hoa Binh Dam in Vietnam,including horizontal displacement,time,reservoir water level,and air temperature,are used for the experiments.The results indicate that all of these three methods can approximately describe the trend of dam deformation despite their different forecast accuracies.Hence,their short-term forecasts can provide valuable references for the dam safety.
摘要:If left unmodeled,the delay suffered by electromagnetic waves while crossing the neutral atmosphere negatively affects Global Navigation Satellite System positioning.The modeling of the delay has been carried out by means of empirical models formulated based on climatological information or using information extracted from numerical weather prediction (NWP) models.This paper explores the potential use of meteorological information of several types that will become available with the increasing number of sensors (e.g.a cell phone,or the thermometer of a nearby smart home) in cyberspace.How can we make use of these potentially huge datasets,which may help to provide the best possible representation of the neutral atmosphere at any given time,as readily and as accurately as possible? This situation falls in the realm of Big Data.A few potential scenarios,a sequential improvement of Marini mapping function coefficients,a self-feeding NWP,and near real-time empirical model updates,are discussed in this paper.The pros and cons of each approach are discussed in comparison with what is done today.Experiments indicate that they have potential for a positive contribution.
摘要:Targeting at a reliable image matching of multiple remote sensing images for the generation of digital surface models,this paper presents a geometric-constrained multi-view image matching method,based on an energy minimization framework.By employing a geometrical constraint,the cost value of the energy function was calculated from multiple images,and the cost value was aggregated in an image space using a semi-global optimization approach.A homography transform parameter calculation method is proposed for fast calculation of projection pixel on each image when calculation cost values.It is based on the known interior orientation parameters,exterior orientation parameters,and a given elevation value.For an efffcient and reliable processing of multiple remote sensing images,the proposed matching method was performed via a coarse-to-fine strategy through image pyramid.Three sets of airborne remote sensing images were used to evaluate the performance of the proposed method.Results reveal that the multi-view image matching can improve matching reliability.Moreover,the experimental results show that the proposed method performs better than traditional methods.
摘要:Volunteered geographic information (VGI) has entered a phase where there are both a substantial amount of crowdsourced information available and a big interest in using it by organizations.But the issue of deciding the quality of VGI without resorting to a comparison with authoritative data remains an open challenge.This article first formulates the problem of quality assessment of VGI data.Then presents a model to measure trustworthiness of information and reputation of contributors by analyzing geometric,qualitative,and semantic aspects of edits over time.An implementation of the model is running on a small data-set for a preliminary empirical validation.The results indicate that the computed trustworthiness provides a valid approximation of VGI quality.
摘要:User-Generated Content (UGC) provides a potential data source which can help us to better describe and understand how places are conceptualized,and in turn better represent the places in Geographic Information Science (GIScience).In this article,we aim at aggregating the shared meanings associated with places and linking these to a conceptual model of place.Our focus is on the metadata of Flickr images,in the form of locations and tags.We use topic modeling to identify regions associated with shared meanings.We choose a grid approach and generate topics associated with one or more cells using Latent Dirichlet Allocation.We analyze the sensitivity of our results to both grid resolution and the chosen number of topics using a range of measures including corpus distance and the coherence value.Using a resolution of 500 m and with 40 topics,we are able to generate meaningful topics which characterize places in London based on 954 unique tags associated with around 300,000 images and more than 7000 individuals.
摘要:The paper discusses the need of a high-level query language to allow analysts,geographers and,in general,non-programmers to easily cross-analyze multi-source VGI created by means of apps,crowd-sourced data from social networks and authoritative geo-referenced data,usually represented as JSON data sets (nowadays,the de facto standard for data exported by social networks).Since an easy to use high-level language for querying and manipulating collections of possibly geo-tagged JSON objects is still unavailable,we propose a truly declarative language,named J-CO-QL,that is based on a well-defined execution model.A plug-in for a GIS permits to visualize geo-tagged data sets stored in a NoSQL database such as MongoDB;furthermore,the same plug-in can be used to write and execute J-CO-QL queries on those databases.The paper introduces the language by exemplifying its operators within a real study case,the aim of which is to understand the mobility of people in the neighborhood of Bergamo city.Cross-analysis of data about transportation networks and VGI from travelers is performed,by means of J-CO-(L language,capable to manipulate and transform,combine and join possibly geo-tagged JSON objects,in order to produce new possibly geo-tagged JSON objects satisfying users' needs.
摘要:The paper designs an automated valuation model to predict the price of residential property in Coventry,United Kingdom,and achieves this by means of geostatistical Kriging,a popularly employed distance-based learning method.Unlike traditional applications of distance-based learning,this papers implements non-Euclidean distance metrics by approximating road distance,travel time and a linear combination of both,which this paper hypothesizes to be more related to house prices than straight-line (Euclidean) distance.Given that-to undertake Kriging-a valid variogram must be produced,this paper exploits the conforming properties of the Minkowski distance function to approximate a road distance and travel time metric.A least squares approach is put forth for variogram parameter selection and an ordinary Kriging predictor is implemented for interpolation.The predictor is then validated with 10-fold cross-validation and a spatially aware checkerboard hold out method against the almost exclusively employed,Euclidean metric.Given a comparison of results for each distance metric,this paper witnesses a goodness of fit (r2) result of 0.6901 ± 0.18 SD for real estate price prediction compared to the traditional (Euclidean) approach obtaining a suboptimal r2 value of 0.66 ± 0.21 SD.
摘要:Nowadays,several research projects show interest in employing volunteered geographic information (VGI) to improve their systems through using up-to-date and detailed data.The European project CAP4Access is one of the successful examples of such international-wide research projects that aims to improve the accessibility of people with restricted mobility using crowdsourced data.In this project,OpenStreetMap (OSM) is used to extend OpenRouteService,a well-known routing platform.However,a basic challenge that this project tackled was the incompleteness of OSM data with regards to certain information that is required for wheelchair accessibility (e.g.sidewalk information,kerb data,etc.).In this article,we present the results of initial assessment of sidewalk data in OSM at the beginning of the project as well as our approach in awareness raising and using tools for tagging accessibility data into OSM database for enriching the sidewalk data completeness.Several experiments have been carried out in different European cities,and discussion on the results of the experiments as well as the lessons learned are provided.The lessons learned provide recommendations that help in organizing better mapping party events in the future.We conclude by reporting on how and to what extent the OSM sidewalk data completeness in these study areas have benefited from the mapping parties by the end of the project.
地球空间信息科学学报(英文版)的期刊信息
曾用名:武测译文
创刊时间:1998
地区:CN
语言:中文
热门主题:武汉大学
学科分类:
4
Earth and Planetary Sciences:Computers in Earth Sciences;Social Sciences:Geography, Planning and Development;