共查询到20条相似文献，搜索用时 15 毫秒
1.
Reducing Influence of Gravity Model Error in Precise Orbit Determination of Low Earth Orbit Satellites 总被引：1，自引：0，他引：1
GUO Jinlai HU Min ZHAO Qile GUO Daoyu 《地球空间信息科学学报》2007,10(2):105-110
Based on the orbit integration and orbit fitting method, the influence of the characters of the gravity model, with different precisions, on the movement of low Earth orbit satellites was studied. The way and the effect of absorbing the influence of gravity model error on CHAMP and GRACE satellite orbits, using linear and periodical empirical acceleration models and the so-called "pseudo-stochastic pulses" model, were also analyzed. 相似文献
2.
利用NOAA-AVHRR数据分析1982-2001年间中国植被的动态变化(英文) 总被引：1，自引：0，他引：1
The authors derived the normalized difference vegetation index (NDVI) from the NOAA/AVHRR Land dataset, at a spatial resolution of 8km and 15-day intervals, to investigate the vegetation variations in China during the period from 1982 to 2001. Then, GIS is used to examine the relationship between precipitation and the Normalized Difference Vegetation Index (NDVI) in China, and the value of NDVI is taken as a tool for drought monitoring. The results showed that in the study period, China’s vegetation cover h... 相似文献
3.
基于能量守恒的星间距离变率与地球重力场频谱关系的建立与分析(英文) 总被引：1，自引：0，他引：1
The spectral relationship between range-rate measurements and the gravity potential for low-low satellite-to-satellite tracking mission was established based on the energy conservation theory. Then the performances of satellite separation, the orbital altitude, and the accuracy of range-rate measurements in recovering the earth’s gravity field were simulated and analyzed by this method. Finally, the cumulative geoid errors of the reference mode were obtained by using the configuration parameters of the GRAC... 相似文献
4.
In this paper, we apply lagged correlation analysis to study the effects of vegetation cover on the summer climate in different
zones of China, using NOAA/AVHRR normalized difference vegetation index (NDVI) data during the time period from 1982 to 2001
and climate data of 365 meteorological stations across China (precipitation from 1982 to 2001 and temperature from 1982 to
1998). The results show that there are positive correlations between spring NDVI and summer climate (temperature and precipitation)
in most zones of China; these suggest that, when the vegetation cover increases, the summer precipitation will increase, and
the lagged correlations show a significant difference between zones. The stronger correlations between NDVI in previous season
and summer climate occur in three zones (Mid-temperate zone, Warm-temperate zone and Plateau climate zone), and this implies
that vegetation changes have more sensitive feedback effects on climate in the three zones in China.
Supported by the National 973 Program of China (No.2006CB701300), the National Natural Science Foundation of China (No.40721001),
the Sino-Germany Joint Project (No. 2006DFB91920), the Open Fund of Shanghai Leading Academic Discipline Project (T0102) and
the Open Fund of LIESMARS, Wuhan University. 相似文献
5.
Based on the gravity field models EGM96 and EIGEN-GL04C, the Earth＇s time-dependent principal moments of inertia A, B, C are obtained, and the variable rotation of the Earth is determined. Numerical results show that A, B, and C have increasing tendencies; the tilt of the rotation axis increases 2.1×10^ 8 mas/yr; the third component of the rotational angular velocity, ω3 , has a decrease of 1.0×10^ 22 rad/s^2, which is around 23% of the present observed value. Studies show in detail that both 0 and ω3 experience complex fluctuations at various time scales due to the variations of A, B and C. 相似文献
6.
申文斌 《地球空间信息科学学报》2009,12(1):1-6
Given a continuous boundary value on the boundary of a "simply closed surface"S that encloses the whole Earth, a regular harmonic fictitious field V*(P) in the domain outside an inner sphere K i that lies inside the Earth could be determined, and it is proved that V*(P) coincides with the Earth’s real field V(P) in the whole domain outside the Earth. Since in the domain outside the inner sphere Ki and the fictitious regular harmonic function V*(P) could be expressed as a uniformly convergent spherical harm... 相似文献
7.
The extraction of points on the bare earth from point clouds acquired by airborne laser scanning is one of the most important
steps for the generation of digital terrain models (DTM). This process is called “filtering”. However, most of the current
filters erode the bare earth in steep sloped landscapes and at discontinuities, and they retain low vegetation. Therefore,
a new filtering method for extracting ground points based on a distance limit is proposed in this paper. The angle criterion
is used to assure the robustness of the algorithm. The experimental results show that the proposed filtering method can effectively
derive the ground points from point clouds in complex urban areas.
Supported by the Program for Changjiang Scholars and Innovative Research Team in University (No.0438), the National 863 Program
of China (No. 2006AA12Z151). 相似文献
8.
In the supervised classification process of remotely sensed imagery, the quantity of samples is one of the important factors affecting the accuracy of the image classification as well as the keys used to evaluate the image classification. In general, the samples are acquired on the basis of prior knowledge, experience and higher resolution images. With the same size of samples and the same sampling model, several sets of training sample data can be obtained. In such sets, which set reflects perfect spectral characteristics and ensure the accuracy of the classification can be known only after the accuracy of the classification has been assessed. So, before classification, it would be a meaningful research to measure and assess the quality of samples for guiding and optimizing the consequent classification process. Then, based on the rough set, a new measuring index for the sample quality is proposed. The experiment data is the Landsat TM imagery of the Chinese Yellow River Delta on August 8th, 1999. The experiment compares the Bhattacharrya distance matrices and purity index zl and △x based on rough set theory of 5 sample data and also analyzes its effect on sample quality. 相似文献
9.
GRACE’s implication of temporal inertia moment and length of day 总被引：2，自引：0，他引：2
This paper aims to study the Earth’s temporal inertia moment and its influence on length of day (LOD). First, the GRACE data
are processed by wavelet analysis to remove abnormal jumps and noises. Then the theoretical impacts of the second-order potential
coefficients on the inertia moment and LOD are studied. Finally, the processed GRACE data are applied and results show that
mass redistribution has led to decreasing tendencies of inertia moment and LOD as well as some unexpected seasonal oscillations
in the recent 6 years.
Supported by the Open Fund of Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, China (No.08-02-02),
the Special Project Fund of State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing (China),
the National 863 Program of China (No.2006AA12Z211). 相似文献
10.
The advanced data mining technologies and the large quantities of remotely sensed Imagery provide a data mining opportunity
with high potential for useful results. Extracting interesting patterns and rules from data sets composed of images and associated
ground data can be of importance in object identification, community planning, resource discovery and other areas. In this
paper, a data field is presented to express the observed spatial objects and conduct behavior mining on them. First, most
of the important aspects are discussed on behavior mining and its implications for the future of data mining. Furthermore,
an ideal framework of the behavior mining system is proposed in the network environment. Second, the model of behavior mining
is given on the observed spatial objects, including the objects described by the first feature data field and the main feature
data field by means of the potential function. Finally, a case study about object identification in public is given and analyzed.
The experimental results show that the new model is feasible in behavior mining.
Supported by the National 973 Program of China(No.2006CB701305,No.2007CB310804), the National Natural Science Fundation of
China (No.60743001), the Best National Thesis Fundation (No.2005047), the National New Century Excellent Talent Fundation
(No.NCET-06-0618). 相似文献
11.
基于簇模型的矢量地图数据的高效压缩方法(英文) 总被引：3，自引：2，他引：1
This paper proposes a new method for the compression of vector data map. Three key steps are encompassed in the proposed method,
namely, the simplification of vector data map via the elimination of vertices, the compression of removed vertices based on
a clustering model, and the decoding of the compressed vector data map. The proposed compression method was implemented and
applied to compress vector data map to investigate its performance in terms of the compression ratio and distortions of geometric
shapes. The results show that the proposed method provides a feasible and efficient solution for the compression of vector
data map and is able to achieve a promising ratio of compression and maintain the main shape characteristics of the spatial
objects within the compressed vector data map.
Supported by the National 863 Program of China (No. 2007AAl2Z241), the Program for New Century Excellent Talents in University
(No. NCET-07-0643), the National Natural Science Foundation of China (No. 40571134, No. 40871185), the National 973 Program
of China (No. 108085). 相似文献
12.
Clonal selection feature selection algorithm (CSFS) based on clonal selection algorithm (CSA), a new computational intelligence approach, has been proposed to perform the task of dimensionality reduction in high-dimensional images, and has better performance than traditional feature selection algorithms with more computational costs. In this paper, a fast clonal selection feature selection algorithm (FCSFS) for hyperspectral imagery is proposed to improve the convergence rate by using Cauchy mutation instea... 相似文献
13.
我国省级空间数据库的一种构建方案(英文) 总被引：2，自引：2，他引：0
In order to provide a provincial spatial database, this paper presents a scheme for spatial database construction to meet
the needs of China. The objective and overall technical route of spatial database construction are described. The logical
and physical database models are designed. Key issues are addressed, such as integration of multi-scale heterogeneous spatial
databases, spatial data version management based on metadata and integrative management of map cartography and spatial database.
Supported by the 863 High Technology Program of China (No. 2007AA12Z214), the National Natural Science Foundation of China
(No. 40601083) and the National Key Basic Research and Development Program of China ( No. 2004CB318206). 相似文献
14.
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 Quad-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 Digital Cartographic Model, and a hybrid model between vector and raster spatial data. Then, the paper studies information visualization mechanism of multimedia electronic map. Finally, the paper certifies the results via a case of multimedia electronic map authoring tools software-Atlas2005. 相似文献
15.
CHEN Xiaoling CAI Xiaobin LI Hui 《地球空间信息科学学报》2007,10(1):37-43
The expert knowledge has been widely used to improve the remotely sensed classification accuracy. Generally, the ex-pert classification system mainly depends on DEM and some thematic maps. The spatial relationship information in pixel level was commonly introduced into the expert classification. Because the geographic objects were found spatially dependent relationship to a certain degree, the commonly used basic unit of spatial relationship information in pixel greatly limited the efficiency of spatial in-formation. A patch-based neighborhood searching algorithm was proposed to implement the expert classification. The homogene-ous spectral unit, patch, was used as the basic unit in the spatial object granularity, and different types of patches' relationship in-formation were obtained through a spatial neighborhood searching algorithm. And then the neighborhood information and DEM data were added into the expert classification system and used to modify the primitive classification errors. In this case, the classi-fication accuracies of wetland, grassland and cropland were obviously improved. In this work, water was used as base object, and different types of water extraction methods were tested to get a result in a high accuracy. 相似文献
16.
The characteristics of three GPS kinematic data processing models, Least Squares （LS）, Kalman filtering and filtering are discussed and their advantages and disadvantages are compared. With observational data and pertinent data processing software, the applicable condition, context and effect of the three models are experimented. Results show that when the mobile platform is in uniform motion, the accuracy of the three models are almost equal; when the mobile platform is in stochastic acceleration, the accuracy of H∞ filtering model is superior to that of LS, while that of Kalman filtering is the worst. 相似文献
17.
一种面向网络发布的海洋数据库引擎(英文) 总被引：1，自引：0，他引：1
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. 相似文献
18.
ZOU Xiancai LI Jiancheng LUO Jia XU Xinyu 《地球空间信息科学学报》2007,10(4):255-259
The characteristics of the normal equation created in recovering the Earth gravity model (EGM) by least-squares(LS) adjustment from the in-situ disturbing potential is discussed in detail. It can be co... 相似文献
19.
Due to the super rotation of the Earth＇s inner core, the tilted figure axis of the inner core would progress with respect 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 0.79-1.54×10^3 pGal and a global average intensity of about 0.45-0.89×10^ 3 μGal in the whole year of 2007, which is beyond the accuracy of the present gravimetry 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 pGal and 0.29 pGal, 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. 相似文献
20.
数字城市共享平台框架的设计与实现(英文) 总被引：2，自引：1，他引：1
This paper proposes a theoretical framework of spatial information sharing in a digital city, and analyzes its technical characteristics.
According to the service-oriented architecture (SOA) framework, a geospatial information sharing platform is put forward.
The spatial information sharing model based on SOA is designed. A prototype platform realizing multiple-source spatial information
sharing based on ArcGIS Server is developed.
Supported by the National Key Basic Research and Development Program of China (No.2004CB318206), the Basic Research of Survey
and Mapping Bureau Project (No.1469990711111). 相似文献