2012 Vol. 37, No. 11
This paper analyzes the characteristics of island,reef and complex environment including sea wave,tide,tidal current and temperature.Then,based on the features of marine complex elements,subdividable object oriented data model(SOODM) has been put forward which applies to high dynamic and strong interactive object effectively.Finally,this paper takes pilot of Zhoushan Islands and realizes the dynamic three-dimensional(3D) modeling of island,reef and surrounding complex environment.The model has been examined on Geoglobe and the result shows the validity and practicability of this model
We propose a qualitative and quantitative approach to automatica construction of the semantic relation between spatial relation terms and feature types of geographical entities.Firstly,all spatial relations annotated in the Corpus are extracted as resource data,and then the “Overlap” similarity measure is used to define the relevance between spatial relation terms and geographical feature types.Secondly,the relevance is introduced as an original weight for the semantic distance computation of geographical concepts in the classification scheme of geographical feature types.Finally,a knowledge base is developed with protégé to formally represent and visualize the classification schemes,spatial relation terms and semantic relations with geographical feature types.This study indicates that our proposed approach can effectively obtain meaningful results.It is noted that the annotation quality of the corpus and the classification granularity of geographical entities have great effect on the performance.
Against the contradictions between model-driven route planning and the diversity of human cognitive preferences for spatial cognition oriented optimal routes,we present a kind of interactive route planning approach based on hierarchical reinforcement learning.In this approach,optimal route criterias are translated into immediate rewards of turning decisions at intersections,and optimal route policies with maximal cumulative rewards can be found through a two-stage learning process.The first pre-learning stage automatically identifies some nodes in road network as subgoals and constructs corresponding subtasks containing local optimal route policies for achieving the subgoals.The second real-time learning stage focuses on efficiently updating the Q values of every available state-action pair using predefined policies,and tracing the optimal routes according to Q values.The experimental results show that our proposed approach learns effectively enough and ensures the routes found close to global optimal ones.
A hybrid spatial clustering method based on graph theory and spatial density(HGDSC) is developed.The HGDSC method employs Delaunay triangulation to model the spatial proximity relationships among spatial entities and the modified density-based clustering method,considering the similarity of both geometric distance and non-spatial attribute.Normally,the method can adapt to a spatial database which contains clusters of arbitrary shapes,non-homogeneous densities and/or large amount of noise.Only one input parameter is required.Experiments on both synthetic and real-world spatial dataset are utilized to demonstrate the effectiveness and advantages of the HGDSC method.
We put forward a new relational matrix,angular matrix.Preliminary research shows that the spectral method of graph is effective for representation and measurement of 2D spatial object's shape and the angular matrix can represent geometric shape of spatial object more accurately and precisely than other relational matrix,such as adjacent matrix,Laplacian matrix,and distance matrix.
The previous spatial interpolation methods have problems on the keeping of local structure and boundary treatment.To overcome these problems,based on the structural properties of the Voronoi on spatial partition,we propose a multi-dimensional unified spatial interpolation algorithm.With random simulated data and the average temperature data of Chinese cities,the experimental results indicate that the proposed interpolation algorithm can support irregular boundary data,and achieve good performance on keeping local structure characteristics and high accuracy.
We describe briefly the basic principle of GPS-supported low-altitude photographic system developed by the authors.A set of actual aerial images with airborne GPS data,at a ground sample distance of 10 cm,were taken from Yicheng site in China by our system.The empirical results have verified that the accuracy of the GPS-supported bundle block adjustment with 4 XYZ ground control points around the corners of the block area is very close to that of the conventional self-calibration bundle block adjustment with additional parameters,which leads to more than 90% reduction in field survey for ground control points.And the object coordinate accuracies of the stereo models reconstructed using the photogrammetric points obtained by GPS-supported bundle block adjustment are better than ±20 cm for planimetry and ±15 cm for elevation,which meets the specification of topographic mapping at 1∶500 scale flat.This shows the ample applicability and the economic benefit of GPS-supported bundle block adjustment in low-altitude photogrammetry.
We introduce the theory and application of digital close range photogrammetry in deformation measurement of mine physical model.A ordinary digital SLR camera is employed and multi-intersection photography is used to take images of mine physical model in the project.The photogrammetric bundle adjustment is applied to compute object space coordinates of artificial deformation monitoring target points on the surface of mine model.Then the cumulative displacement of each deformation monitoring target point is calculated based on their object coordinates and the cumulative displacement vector maps are drawn.The accuracy of plane coordinates is better than ±0.20 mm according to measurement results.The displacement field measured is the same as the actual deformation.The measurement result is satisfactory to the requirement of deformation measurement of mine similar material model.
Shadow detection and compensation in high resolution remote sensing images is very critical for target identification and information recovering.Based on a series of analysis about shadow properties,several properties were selected to compose together to detect shadow.Through improving Otsu method,more suitable thresholds of each property could be acquired automatically,which realized automatic detection of shadow.In order to highlight the information of objects inside shadow areas,an improved shadow compensation strategy based on the Wallis filter principle was proposed.Experiments indicate that the detection method is effective,and the accuracy and application range are improved,the compensation result is outstanding,and details sheltered by shadow also reappear.
A novel algorithm for multi-image matching by using a manifold learning method is presented.The matching algorithm applies the Laplacian Eigenmap algorithm to map feature points from different images to the same embedding space.Meantime,the local and global distribution similarities of feature points are calculated by SIFT descriptor and location information.Finally,a series of carefully designed experiments on two groups of the wide-baseline image sequences are designed to demonstrate and validate the performance of the proposed algorithm,which is higher than that of the LE-SIFT,SVD-SIFT and LLE-SVD methods in multi-image matching and stereo matching under the multi-image constrains.
We present an automatic building facade extraction approach based on terrestrial laser scanning points,which effectively use the ant colony algorithm to remove the occlusions and get rid of the error points caused by windows.The method is tested with terrestrial point clouds of three different street scenes.The results show that the method is effective.
We present a novel method for automated extraction of building facade footprints from mobile LiDAR point clouds.The proposed method first generates the georeferenced feature image of a mobile LiDAR point cloud and then uses image segmentation to extract contour areas which contain facade points of buildings,points of trees and points of other objects in the georeferenced feature image.After all the points in each contour area are extracted,a classification based on eigenvalue analysis and profile analysis is adopted to identify building objects from point clouds extracted in contour areas.Then all the points in a building object are segmented into different planes using RANSAC algorithm.For each building,points in facade planes are chosen to calculate the direction,the start point,and the end point of the facade footprint using eigenvalue analysis.Finally,footprints of different facades of building are refined,harmonized,and joined.The experimental results show that the proposed method provides a promising and valid solution for automatically extracting building facade footprints from mobile LiDAR point clouds.
To avoid the spectral distortion of SVR(synthetic variable ratio) algorithm,we propose an improved algorithm by using a low-pass filter and histogram matching performance,which is hence named SVR based on low-pass filter and histogram matching(SVRFM) algorithm.Two subsets from the IKONOS image of Fuzhou,representing different land cover types were used as test data.The spectral fidelity and the ability of gaining high frequency information were assessed by using visual and statistical analysis.The fused images were compared with those fused using the SVR,wavelet transform,pansharp,ehlers and Gram-Schmidt algorithms,respectively.The results show that the spectral fidelity of the SVRFM algorithm is generally better than the five algorithms compared.
By comparing and analyzing the sensor difference between MODIS and HJ-IRS,we present a newly improved forest fire hotspot detection method which is adaptive to HJ-IRS through improving a new cloud and water mask method and adjusting the threshold value in the MODIS version 4 contextual algorithm.With Heilongjiang area of China and the Far-east area of Russia as the research object,by comparative analysis with the MODIS hotspot products of same area and same time adopting the V4 Algorithm,we find that IRS hotspot product has the same spatial distribution with MODIS,without leak detection.With respect to low temperature small hotspot and its geometric location,HJ-IRS has a preferable performance.
For digital stereo mapping with SAR images,we propose a method for generation of SAR ideal stereo model from which good stereo vision is achieved and high precise three-dimensional geographic coordinates can be measured.Ideal stereo model was made using high resolution airborne SAR images collected in Hengduan Mountain area and used for digital stereo mapping experiments.Therefore,good results have been achieved.
To eliminate the pervasive geometric distortion and improve the application value of SAR images,orthorectification taking topography into account must be performed to generate orthoimages in a certain map projection.This process is known as SAR geocoding.To solve the problems of traditional methods for SAR geocoding in efficiency and accuracy,here a modified 3D grid interpolation method is proposed.Experimental results with ENVISAT ASAR data show that significant improvements in geometric location accuracy can be achieved by using the modified method when compared with the original one,while the increases in computation time cost are limited.Therefore,the modified 3D grid interpolation method can be used to perform fast SAR image geocoding with high accuracy.
The processing capacity for GPS data with clock jumps using four online PPP services(CSRS-PPP,APPS,GAPS,and magicGNSS) are analyzed.The experimental results show that,CSRS-PPP is the most robust service which can effectively deal with the millisecond-level(ms) jumps and avoid the effects on positioning.However it is incapable of the frequent microsecond-level(μs) jumps.APPS can effectively solve the adverse effects of first type ms jumps,but invalid for the second type of ms jumps.GAPS is totally invalid for the first two types of ms jumps for lack of necessary control,which leads to unnecessary re-initializations and unpredicted results.As to magicGNSS,even for the clean data without any clock jump,its positioning results are terrible,and the phenomenon of failure solution often appear.In addition,a brief test of the capacity for clock jumps with TriP 3.0 is presented.The results show that TriP can deal with all the types of clock jumps with a good performance.
We introduce GPS tracking station and the field GPS work in summer from 2005 to 2010,and give the yearly horizontal and vertical velocities on the surface of the two glaciers,which indicates that the horizontal velocity is from 5.277～8.256 m·a-1 on glacier Pedersenbreen,and from 0.360～3.986 m/a on glacier Austre Lovénbreen.The velocity of surface altitude change is from-3.4～-71.8 cm/a on glacier Pedersenbreen and from +9.6～-115.8 cm/a on glacier Austre Lovénbreen.It shows that the mass balance in two glaciers is negative,and the two glaciers are increasingly melting.
Melbourne-Wubbena(MW) and Geometry-Free(GF) combinations are usually used for cycleslip detection in real-time dynamic PPP,but wind-up error caused by the rotating of receiver's antenna,is usually ignored.We discuss the influences of wind-up error on MW and GF combinations.The analysis and experimental results show that wind-up error has no influence on MW combinations while it will affect GF combinations.Sometimes it may even cause a false cycle-slip detection by using GF combinations.Considering the influences of wind-up error on GF combinations,this essay proposes that with both undifferenced GF combinations and the differenced combinations between satellites a new method can be sused to detect the cycle-slip in real-time dynamic PPP and it shows the new method can successfully eliminate the effect of wind-up error.
The coseismic displacements of Mw9.0 Tohoku-Oki earthquake was analyzed with some GPS fiducial stations located in China east coasts,which using epoch-by-epoch PPP and sidereal filtering technique.The result shows an apparent displacement along horizontal and vertical directions,whose amplitude is about 10 cm.However,after the earthquake,there is no obvious permanent displacements more than 1 cm,which agrees with the results of the domestic and foreign relevant groups,and proves the effectiveness of PPP technology used for coseismic displacements analysis.
We analyze the gravity data observed before and after March 11,2011 when the Mw9.0 earthquake occurred in the sea areas nearby the East coast of Honshu,Japan,with the method of co-seismic response signal analysis.We also provide the observations of long-period seismic surface waves and free oscillations recorded by gPhone gravimeter after the great earthquakes.Processed by band-pass filter,the data obtained within 12 hours after the earthquake can be recognized the records of 7 Rayleigh surface waves spreading around the Earth.In the low frequency domain(5 mHz or less),43 fundamental modes and at least 52 harmonic modes of Earth's free oscillations can be detected,the distributions of which are in good agreement with the theoretical modes.Meanwhile,at the low frequencies less than 1 mHz,spectral splitting of 4 modes is observed.
According to the integrated test task of Beidou system,the evaluation methods and algorithms of system performance,such as service area,accuracy,continuity and availability are proposed.The results show that Beidou system is stable and reliable,and its positioning accuracy,continuity,availability are better than 20 m(95%),0.92/h and 90% respectively.From these results,it can be expected that the Beidou system can provide reliable and good quality PNT services in the future.
According to the characters of regional navigation satellite system,there are some problems that GEO and IGSO satellite may maneuver and less than 4 available navigation satellites could be used during its early building stage.We propose a type of navigation strategy which adopt Receiver Autonomous Integrity Monitoring faults detection,exclusion method and three stars positioning approach and ill conditioning of normal equation resolution to overcome these problems.Then the validation and continuity of navigation satellite system in ordinary application fields can be improved.By handling the actual data,the feasibility of these approaches is verified.
Based on geostatistics principal,the global spatial-temporal partition features are investigated detailedly using IONEX products derived from IGS.Moreover,release policy of IONEX products is provided for IGS.Then,VTEC partition modeling methods which include both combination function method and IRI2007 background field method are presented.In the end,VTEC modeling results and analysis show that partition modeling greatly reduces the complexity of the model,and VTEC RMSE of low latitude partition B13 is invariably about two times that of high latitude partition A23 for two methods.So,VTEC partition modeling is proved to be effective and reliable.
If a deep space tracking station is founded in Earth's Antarctic area,communication conditions will be greatly improved attributing to its broader vision.This paper assumes the deep space station is established in Chinese Antarctica Great-Wall station,and simulates the communication accessibility between the lunar rover and the Great-Wall tracking station.Through the comparison with the domestic tracking station's communication condition,the results show that:① The influence of communication condition by topography between the lunar rover in lunar south pole and Great-Wall tracking station is less than that between the lunar rover in lunar south pole and the domestic tracking stations.② The longitude is about 180° from the Chinese Antarctic Great-Wall station to the domestic tracking station.Integrated with all of the tracking stations,including Chinese Antarctic Great-Wall station and domestic tracking stations,the impact of the stations away from the Moon due to the Earth's rotation can be reduced and the tracking time can be lengthened.The simulation and analysis of communication accessibility for choosing Antarctic Great-Wall station as deep space tracking station,can provide a suggestion for the feasibility of construction of the next deep space tracking stations.
The lunar gravity anomaly is the basis of the studies followed such as the lunar internal structure and density imaging.Thus,based on the perspective of the physical meaning,we tried to give a reasonable method of lunar gravity anomaly calculation and then analyzed the related influencing factors.Finally,the lunar global Bouguer gravity anomalies with a clear physical meaning were obtai`ned and the preliminary geological interpretation was given for the results.
We introduce the gap of mean square error variances,corre-lation coefficient,signal-nosie ratio and flatness to analyze the relationship between the denoising result of different wavelet strategies and indicator.The result shows that the RMS of wavelet denoising strategy is positively correlated with the trend of the four indicators and the correlation coefficient is 0.95,which is different from wavelet decomposition and reconstruction phase.We use normali-zed composite indicator to replace the unknownRMS to evaluate the denoising effect,and regard denoising residual distribution as reliability qualitative indicator.
In order to adapt new underground 3D traffic method of pipe replaced by box culvert jacking process,a set of automatic guidance system based on total station was developed.This paper introduced the principle and key techniques of this system,and combined with successful application of culvert jacking highway under the existing railway project in Shanghai Jinshan.In actual construction this system proved to be excellent and have the following features:automatic,reliable,accurate,and it could provide real-time deviation for correction to achieve information construction.
The problem of the analytical transformations between Lagrange and the commonly used conformal projections is discussed with the help of complex numbers theory.The forward and inverse expressions of Lagrange projection by complex numbers are derived,and the mathematical modes of the analytical transformations between Lagrange and Gauss,Mercator,Lambert conformal conic projections by complex numbers are systematically established.The formulae derived by the paper are in the symbolic form including the first eccentricity of the reference ellipsoid,so they could solve the transformation problems when different reference ellipsoids are used.Compared to traditional transformation formulae in the real number domain,they have more concise structure and stricter theory basis,and are more convenient for practical use.