首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 937 毫秒
1.
In this paper,factors lead to changes ande what changes should be considered are firstly discussed.then changes to be represented by set theory is given.Twelve basic change types are described in detail.At last the paper points out that the change between geoobjects and pixels in images is not all corresponging and it causes the difficulty of accurate and robust change detection techniques.  相似文献   

2.
IntroductionCurves are the fundamental geometric elementsin GIS. The uncertainty of their positions has ani mportant influence on those outputs from GISandis the reliable basis for reasonably evaluatingthose outputs .In contrast to measurement error theor…  相似文献   

3.
This paper presents the studies of the refining of IKONOS-2 RPC, the transform of the datum, the mode of the control point distribution and the method of IKONOS stereo triangulation, so that IKONOS imagery can be used to collect the precise geospatial data and produce the large scale map. The transform between the IKONOS-2 image space and the national coordinate system based on the RPC have been developed, and the results of block adjustment with various control schemes in a practical project near Himalayas have been examined and analysed. The encouraging results of high positioning accuracy have been obtained.  相似文献   

4.
Ionospheric delay is a dominant error source in Global Navigation Satellite System (GNSS). Single-frequency GNSS applications require ionospheric correction of signal delay caused by the charged particles in the earth’s ionosphere. The Chinese Beidou system is developing its own ionospheric model for single-frequency users. The number of single-frequency GNSS users and applications is expected to grow fast in the next years in China. Thus, developing an appropriate ionospheric model is crucially important for the Chinese Beidou system and worldwide single-frequency Beidou users. We study the performance of five globally accessible ionospheric models Global Ionospheric Map (GIM), International Reference Ionosphere (IRI), Parameterized Ionospheric Model (PIM), Klobuchar and NeQuick in low- and mid-latitude regions of China under mid-solar activity condition. Generally, all ionospheric models can reproduce the trend of diurnal ionosphere variations. It is found that all the models have better performances in mid-latitude than in low-latitude regions. When all the models are compared to the observed total electron content (TEC) data derived from GIM model, the IRI model (2012 version) has the best agreement with GIM model and the NeQuick has the poorest agreement. The RMS errors of the IRI model using the GIM TEC as reference truth are about 3.0–10.0 TECU in low-latitude regions and 3.0–8.0 TECU in mid-latitude regions, as observed during a period of 1 year with medium level of solar activity. When all the ionospheric models are ingested into single-frequency precise point positioning (PPP) to correct the ionospheric delays in GPS observations, the PIM model performs the best in both low and mid-latitudes in China. In mid-latitude, the daily single-frequency PPP accuracy using PIM model is ~10 cm in horizontal and ~20 cm in up direction. At low-latitude regions, the PPP error using PIM model is 10–20 cm in north, 30–40 cm in east and ~60 cm in up component. The single-frequency PPP solutions indicate that NeQuick model has the lowest accuracy among all the models in both low- and mid-latitude regions of China. This study suggests that the PIM model may be considered for single-frequency GNSS users in China to achieve a good positioning accuracy in both low- and mid-latitude regions.  相似文献   

5.
The unceasing change problem of land information systems can be resolved through the refactoring and design pattern. To promote the implementation of design pattern and refactoring methods in developin...  相似文献   

6.
The present investigation has been designed to analyze the landform and soil relationship in a geologically complex terrain of Tirora tahsil of Gondia district, Maharashtra using remotely sensed data and GIS technique. The geomorphologic units of the study area were delineated through visual interpretation of IRS–ID LISS-III data based on the spatial variation of the image characteristics. Thirteen landform units have been identified in the tahsil. The slope varied from level to nearly level with an area of about 63.76% of the tahsil. Rest of the area ranged from very gentle to moderately steep slopes. During soil survey, soil profiles were studied for morphological features. Horizon-wise soil samples were collected from the representative soil profiles on each landform unit. The depth of soil varied from 25 to 160 cm and colour from dark brown to very dark grayish brown. The texture ranged from clay loam to clayey in accordance with higher and lower topographic positions respectively. Higher available water holding capacity (AWC 285 mm) is found in low-lying area and low to medium AWC (140 mm) is noticed in the soils developed at higher elevation. The soils reaction (pH) is strongly acidic in nature (pH 5.2) on dissected hills, linear ridge and moderately weathered pediments, whereas, the soils are moderately to slightly acidic in nature (pH 5.5 to 6.5) on hills, shallow weathered pediments, moderately weathered pediments, deeply weathered pediments, narrow valleys, and broad valley floors. Slightly alkaline condition (pH 7.6) was observed on foot slopes and aggraded valley fills. The electrical conductivity of the soils is found almost same in all landforms. The cation exchange capacity of the area varies from 10.5 to 51.5 cmol(p+)kg?1. The base saturation increases with decreasing elevation and slope. The four major soil orders viz, Entisols, Alfisols, Inceptisols and Vertisols are found in the study areas which are further classified into suborder and great group levels. The landform and soil relationship was analyzed to appraise the land resources in the tahsil. The study shows that the application of remotely sensed data and GIS are immensely helpful in land resources appraisal for their management on sustainable basis.  相似文献   

7.
Eutrophication in lakes, estuaries and rivers occur due to over-enrichment with nutrients. Amongst the various nutrients Nitrogen (N) and Phosphorous (P) are the elements which are considered as the major pollutants. The present study looks into the problem of managing nutrient losses both from point sources and diffuse sources. The study was carried out in the River R?nne? catchment in South of Sweden where N and P have been assessed by creation of a pollution inventory based on GIS technology. The nutrient loads from different land use types were estimated using export coefficients and evaluated using monitoring data. A comparative analysis is done on the measured and estimated N and P leaching from diffused sources and point sources. Protective zones were suggested to decrease the P export from agricultural land, and the distribution of construction cost was analyzed among administrative regions according to the proportion of catchments, cultivated land, nutrient leaching, protective zone and length of river section within each municipality. The estimated error of the nutrient amount from landuse using GIS is 9.75% and 12.71% for N and P, respectively. The diffused sources contribute 91.53% and 94.74% of the total N and total P respectively, so the creation of a protective zone could be an effective way to decrease the nutrient export. The study demonstrates the power of GIS as a tool to analyze problems related to environmental monitoring and planning at administrative level, which could help in decision making and support for better management of the water resources.  相似文献   

8.
In this study, linear spectral mixture analysis (LSMA) is used to characterize the spectral heterogeneity of lava flows from Nyamuragira volcano, Democratic Republic of Congo, where vegetation and lava are the two main land covers. In order to estimate fractions of vegetation and lava through satellite remote sensing, we made use of 30 m resolution Landsat Enhanced Thematic Mapper Plus (ETM+) and Advanced Land Imager (ALI) imagery. 2 m Pleiades data was used for validation. From the results, we conclude that (1) LSMA is capable of characterizing volcanic fields and discriminating between different types of lava surfaces; (2) three lava endmembers can be identified as lava of old, intermediate and young age, corresponding to different stages in lichen growth and chemical weathering; (3) a strong relationship is observed between vegetation fraction and lava age, where vegetation at Nyamuragira starts to significantly colonize lava flows ∼15 years after eruption and occupies over 50% of the lava surfaces ∼40 years after eruption. Our study demonstrates the capability of spectral unmixing to characterize lava surfaces and vegetation colonization over time, which is particularly useful for poorly known volcanoes or those not accessible for physical or political reasons.  相似文献   

9.
The multispectral and multitemporal analysis of the spectral response of rice has made it possible to determine at which point in the vegetative cycle of rice it is best to make an inventory, together with the usefulness of the normalized‐difference vegetation index for such an inventory. The results could be usefully included in any classification procedure of the TM image in order to make the inventory in a systematic way. In this case a supervised classification of the image has been made which assumes a Gaussian behaviour for each spectral class. The results obtained are, for the most part, consistent with those obtained by using traditional methods.  相似文献   

10.
The policy of the Chinese government concerning the horizontal expansion of the cultivated land through the reclamation of desert soils result in a total increase of 665. 985 km^2 during the period 1987-1999 in North Shaanxi. This increase is less than the loss in arable land by urbanization. The accelerated rate of change in agricultural areas calls for more rapid surveys of urbanization and loss of arable land. Remote sensing has a number of advantages over ground-based methods for such surveys. The multi-scale concept of remote sensing data help us study the problem in four towns. Several maps were produced to analyze the situation of urban coverage in different times. The evaluation of the status, rate and risk of urbanization are based on an accepted average of urban increase as 2% of population growth per year.  相似文献   

11.
The global landscape in the supply, co-creation and use of geospatial data is changing very rapidly with new satellites, sensors and mobile devices reconfiguring the traditional lines of demand and supply and the number of actors involved. In this paper we chart some of these technology-led developments and then focus on the opportunities they have created for the increased participation of the public in generating and contributing information for a wide range of uses, scientific and non. Not all this information is open or geospatial, but sufficiently large portions of it are to make it one of the most significant phenomena of the last decade. In fact, we argue that while satellite and sensors have exponentially increased the volumes of geospatial information available, the participation of the public is transformative because it expands the range of participants and stakeholders in society using and producing geospatial information, with opportunities for more direct participation in science, politics and social action.  相似文献   

12.
Better understanding of the relationship between lake’s water area and water level plays an important role for the monitoring of floods and droughts. At present, there are many analysis and research on the relationship between water area and level, but the estimation criteria are mostly based on ordinary least square, which has no ability to resist the gross error. In this paper, the equivalent weight estimation method with robustness ability is introduced. We use the proposed method in study of the Poyang Lake which is the largest freshwater lake in China. The area extraction data and water level records spans the period from 2009 to 2013. Four models (linear, exponential, logarithmic and quadratic polynomial) of water area and water level are constructed by regression analysis. Meanwhile, two kinds of common weight function factors are applied to analyze the quadratic curve model. The experimental results show that the quadratic polynomial fitting performs best, and the solution of the equivalent weight function method is closer to the realism than least square. We note that the proposed robust estimation method can dynamically monitor the water area and water level, which provides a theoretical basis for similar research.  相似文献   

13.
The temporal change of the rotation vector of a rotating body is, in the first order, identical in a space-fixed system and in a body-fixed system. Therefore, if the motion of the rotation axis of the earth relative to a space-fixed system is given as a function of time, it should be possible to compute its motion relative to an earth-fixed system, and vice versa. This paper presents such a transformation. Two models of motion of the rotation axis in the space-fixed system are considered: one consisting only of a regular (i.e., strictly conical) precession and one extended by circular nutation components, which are superimposed upon the regular precession. The Euler angles describing the orientation of the earth-fixed system with respect to the space-fixed system are derived by an analytical solution of the kinematical Eulerian differential equations. In the first case (precession only), this is directly possible, and in the second case (precession and nutation), a solution is achieved by a perturbation approach, where the result of the first case serves as an approximation and nutation is regarded as a small perturbation, which is treated in a linearized form. The transformation by means of these Euler angles shows that the rotation axis performs in the earth-fixed system retrograde conical revolutions with small amplitudes, namely one revolution with a period of one sidereal day corresponding to precession and one revolution with a period which is slightly smaller or larger than one sidereal day corresponding to each (prograde or retrograde) circular nutation component. The peculiar feature of the derivation presented here is the analytical solution of the Eulerian differential equations.  相似文献   

14.
The mathematic theory for uncertainty model of line segment are summed up to achieve a general conception, and the line error hand model of εσ is a basic uncertainty model that can depict the line accuracy and quality efficiently while the model of εm and error entropy can be regarded as the supplement of it. The error band model will reflect and describe the influence of line uncertainty on polygon uncertainty. Therefore, the statistical characteristic of the line error is studied deeply by analyzing the probability that the line error falls into a certain range. Moreover, the theory accordance is achieved in the selecting the error buffer for line feature and the error indicator. The relationship of the accuracy of area for a polygon with the error loop for a polygon boundary is deduced and computed.  相似文献   

15.
IntroductionIn GPS data-processing, the most accurate andpopular method is to solve the unknown parametersbased on a GPS network which includes many GPSsites. This mode is always called network-solution.The network-solution makes use of the spatial geom-e…  相似文献   

16.
In general, to reconstruct the accurate shape of buildings, we need at least one stereomodel (two photographs) for each building. In most cases, however, only a single non-metric photograph is availabl...  相似文献   

17.
Journal of Geographical Systems - The link between income inequality and economic growth remains poorly understood. The global economic crisis challenged numerous growth studies by highlighting...  相似文献   

18.
The Chinese Loess Plateau has experienced drastic human-induced ecological degradation in the last century. The Chinese government has initiated a longterm project to restore the ecology and thus the environment. This effort requires information about the ecological potential, especially about the potential distribution of forests. This study first presented a complete procedure for spatially modeling the potential distribution of broadleaved deciduous forests (BDF) in the western part of the Chinese Loess Plateau. The procedure efficiently integrated the spatially distributed environmental variables using a machine learning approach (i.e., GARP) that extracted rules and patterns from the massive datasets. The GARP-produced composite map revealed that BDF can potentially be distributed continuously in almost all of the areas where annual precipitation is above 450 mm and BDF has discontinuous or sporadic distribution in areas where annual precipitation is below 450 mm. The discontinuously distributed BDF occurs in two different physiographic settings. The first setting is the higher-elevation mountains within the area between 450 and 400 mm isohyets, where effective soil moisture is considerably higher than low-elevation valleys due to reduced evaporation and increased precipitation. The second setting is the north-facing slopes of rocky terrain within the area north to the 450 mm isohyet, where evaporation is significantly reduced. We believe that the modeled result can effectively facilitate forestation planning for this area. In addition, the results may function as a base against which to estimate the historic changes in land cover and land use, to assess the ecological potential for carbon sequestration, and to evaluate the climatic significance of land-air interactions.  相似文献   

19.
There have been rapid population and accelerating urban growth with associated changes in land use and soil degradation in northeast China, an important grain-producing region. The development of integrated use of remote sensing, geographic information systems, and combined cellular automata– Markov models has provided new means of assessing changes in land use and land cover, and has enabled projection of trajectories into the future. We applied such techniques to the prefecture-level city of Harbin, the tenth largest city in China. We found that there had been significant losses of the land uses termed “cropland”, “grassland”, “wetland”, and “floodplain” in favour of “built-up land” and lesser transformations from “floodplain” to “forestland” and “water body” over the 18-year period. However, the transition was not a simple process but a complex network of changes, interchanges, and multiple transitions. In the absence of effective land use policies, projection of past trajectories into a balance state in the future would result in the decline of cropland from 65.6% to 46.9% and the increase of built-up area from 7.7% to 23.0% relative to the total area of the prefecture in 1989. It also led to the virtual elimination of land use types such as unused wetland and floodplain.  相似文献   

20.
This study investigates urbanization and its potential environmental consequences in Shanghai and Stockholm metropolitan areas over two decades. Changes in land use/land cover are estimated from support vector machine classifications of Landsat mosaics with grey-level co-occurrence matrix features. Landscape metrics are used to investigate changes in landscape composition and configuration and to draw preliminary conclusions about environmental impacts. Speed and magnitude of urbanization is calculated by urbanization indices and the resulting impacts on the environment are quantified by ecosystem services. Growth of urban areas and urban green spaces occurred at the expense of cropland in both regions. Alongside a decrease in natural land cover, urban areas increased by approximately 120% in Shanghai, nearly ten times as much as in Stockholm, where the most significant land cover change was a 12% urban expansion that mostly replaced agricultural areas. From the landscape metrics results, it appears that fragmentation in both study regions occurred mainly due to the growth of high density built-up areas in previously more natural/agricultural environments, while the expansion of low density built-up areas was for the most part in conjunction with pre-existing patches. Urban growth resulted in ecosystem service value losses of approximately 445 million US dollars in Shanghai, mostly due to the decrease in natural coastal wetlands while in Stockholm the value of ecosystem services changed very little. Total urban growth in Shanghai was 1768 km2 and 100 km2 in Stockholm. The developed methodology is considered a straight-forward low-cost globally applicable approach to quantitatively and qualitatively evaluate urban growth patterns that could help to address spatial, economic and ecological questions in urban and regional planning.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号