共查询到20条相似文献，搜索用时 38 毫秒
1.
Area-based tests for association between spatial patterns 总被引：2，自引：0，他引：2
Edge effects pervade natural systems, and the processes that determine spatial heterogeneity (e.g. physical, geochemical,
biological, ecological factors) occur on diverse spatial scales. Hence, tests for association between spatial patterns should
be unbiased by edge effects and be based on null spatial models that incorporate the spatial heterogeneity characteristic
of real-world systems. This paper develops probabilistic pattern association tests that are appropriate when edge effects
are present, polygon size is heterogeneous, and the number of polygons varies from one classification to another. The tests
are based on the amount of overlap between polygons in each of two partitions. Unweighted and area-weighted versions of the
statistics are developed and verified using scenarios representing both polygon overlap and avoidance at different spatial
scales and for different distributions of polygon sizes. These statistics were applied to Soda Butte Creek, Wyoming, to determine
whether stream microhabitats, such as riffles, pools and glides, can be identified remotely using high spatial resolution
hyperspectral imagery. These new “spatially explicit” techniques provide information and insights that cannot be obtained
from the spectral information alone.
Received 1 June 2001 / Accepted 25 October 2001 相似文献
2.
Wolf-Dieter Rase 《Journal of Geographical Systems》2001,3(2):199-213
The interpolation of continuous surfaces from discrete points is supported by most GIS software packages. Some packages provide
additional options for the interpolation from 3D line objects, for example surface-specific lines, or contour lines digitized
from topographic maps. Demographic, social and economic data can also be used to construct and display smooth surfaces. The
variables are usually published as sums for polygonal units, such as the number of inhabitants in communities or counties.
In the case of point and line objects the geometric properties have to be maintained in the interpolated surface. For polygon-based
data the geometric properties of the polygon boundary and the volume should be preserved, avoiding redistribution of parts
of the volume to neighboring units during interpolation. The pycnophylactic interpolation method computes a continuous surface
from polygon-based data and simultaneously enforces volume preservation in the polygons. The original procedure using a regular
grid is extended to surface representations based on an irregular triangular network (TIN).
Received: 5 October 2000 / Accepted: 20 December 2000 相似文献
3.
Colin Robertson Trisalyn A. Nelson Barry Boots Michael A. Wulder 《Journal of Geographical Systems》2007,9(3):207-227
Research questions regarding temporal change in spatial patterns are increasingly common in geographical analysis. In this
research, we explore and extend an approach to the spatial–temporal analysis of polygons that are spatially distinct and experience
discrete changes though time. We present five new movement events for describing spatial processes: displacement, convergence,
divergence, fragmentation and concentration. Spatial–temporal measures of events for size and direction are presented for
two time periods, and multiple time periods. Size change metrics are based on area overlaps and a modified cone-based model
is used for calculating polygon directional relationships. Quantitative directional measures are used to develop application
specific metrics, such as an estimation of the concentration parameter for a von Mises distribution, and the directional rate
of spread. The utility of the STAMP methods are demonstrated by a case study on the spread of a wildfire in northwestern Montana.
相似文献
4.
Computer networks like the Internet are gaining importance in social and economic life. The accelerating pace of the adoption
of network technologies for business purposes is a rather recent phenomenon. Many applications are still in the early, sometimes
even experimental, phase. Nevertheless, it seems to be certain that networks will change the socioeconomic structures we know
today. This is the background for our special interest in the development of networks, in the role of spatial factors influencing
the formation of networks, and consequences of networks on spatial structures, and in the role of externalities. This paper
discusses a simple economic model – based on a microeconomic calculus – that incorporates the main factors that generate the
growth of computer networks. The paper provides analytic results about the generation of computer networks. The paper discusses
(1) under what conditions economic factors will initiate the process of network formation, (2) the relationship between individual
and social evaluation, and (3) the efficiency of a network that is generated based on economic mechanisms.
Received: 5 July 2000 / Accepted: 28 November 2000 相似文献
5.
Change detection thresholds for remotely sensed images 总被引：4，自引：0，他引：4
Peter A. Rogerson 《Journal of Geographical Systems》2002,4(1):85-97
The detection of change in remotely sensed images is often carried out by designating a threshold to distinguish between
areas of change and areas of no change. The choice of threshold is often arbitrary however. The purpose of this paper is to
offer a statistical framework for the selection of thresholds. The framework accounts for the facts that one carries out multiple
tests of the null hypothesis of no change, when searching for regions of change over an image with a large number of pixels.
Special attention is given to global spatial autocorrelation, which can affect the selection of appropriate threshold values.
Received: 8 March 2001 / Accepted: 12 October 2001 相似文献
6.
LIU Chun TONG Xiaohua 《地球空间信息科学学报》2005,8(3):183-188
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
7.
This paper discusses a modeling approach for spatial-temporal prediction of environmental phenomena using classified satellite
images. This research was prompted by the analysis of change and landscape redistribution of petroleum residues formed from
the residue of the burning oil wells in Kuwait (1991). These surface residues have been termed “tarcrete” (El-Baz et al. 1994).
The tarcrete forms a thick layer over sand and desert pavement covering a significant portion of south-central Kuwait. The
purpose of this study is to develop a method that utilizes satellite images from different time steps to examine the rate-of-change
of the oil residue deposits and determine where redistribution is are likely to occur. This problem exhibits general characteristics
of environmental diffusion and dispersion phenomena so a theoretical framework for a general solution is sought. The use of
a lagged-clique, Markov random field framework and entropy measures is deduced to be an effective solution to satisfy the
criteria of determination of time-rate-of-change of the surface deposits and to forecast likely locations of redistribution
of dispersed, aggraded residues. The method minimally requires image classification, the determination of time stationarity
of classes and the measurement of the level of organization of the state-space information derived from the images. Analysis
occurs at levels of both the individual pixels and the system to determine specific states and suites of states in space and
time. Convergence of the observed landscape disorder with respect to an analytical maximum provide information on the total
dispersion of the residual system.
Received: 5 September 2000 / Accepted: 10 July 2001 相似文献
8.
Shunji Murai Vivarad Phonekeo Kunihiko Ono Shigetaka Yasue 《ISPRS Journal of Photogrammetry and Remote Sensing》1999,54(5-6)
The authors have developed a new method termed “Polygon Shift Method” that enables the generation of a 3D view map of a city with tall buildings with a simplified procedure to shift a polygon and check the overlap between the original and shifted polygon. Boolean operations are applied with a newly defined “Fore or Aft” side and a “Depth Distance” that functionally express the visibility criteria or hidden point processing in the 3D view. Since the polygon shift method can be operated with a raster-based structure, the computer processing for generation of a 3D view map of buildings with shadow is simple and efficient. 相似文献
9.
This study compares two automated approaches, the transect‐from‐baseline technique and a new change polygon method, for quantifying historical coastal change over time. The study shows that the transect‐from‐baseline technique is complicated by choice of a proper baseline as well as generating transects that intersect with each other rather than with the nearest shoreline. The change polygon method captures the full spatial difference between the positions of the two shorelines and average coastal change is the defined as the ratio of the net area divided by the shoreline length. Although then change polygon method is sensitive to the definition and measurement of shoreline length, the results are more invariant to parameter changes than the transect‐from‐baseline method, suggesting that the change polygon technique may be a more robust coastal change method. 相似文献
10.
Asuncion Beamonte Pilar Gargallo Manuel Salvador 《Journal of Geographical Systems》2010,12(2):227-240
In this paper, we extend the Bayesian methodology introduced by Beamonte et al. (Stat Modelling 8:285–311, 2008) for the estimation and comparison of spatio-temporal autoregressive models (STAR) with neighbourhood effects, providing
a more general treatment that uses larger and denser nets for the number of spatial and temporal influential neighbours and
continuous distributions for their smoothing weights. This new treatment also reduces the computational time and the RAM necessities
of the estimation algorithm in Beamonte et al. (Stat Modelling 8:285–311, 2008). The procedure is illustrated by an application to the Zaragoza (Spain) real estate market, improving the goodness of fit
and the outsampling behaviour of the model thanks to a more flexible estimation of the neighbourhood parameters. 相似文献
11.
三角剖分算法是计算几何领域中的重要课题之一,针对现有多边形三角剖分算法大多不能同时兼顾算法的简单有效性、适用性以及三角网的质量问题,提出一种基于自适应分块的任意多边形三角剖分算法。多边形的自适应分块区别于传统的格子分块,它充分顾及了多边形边作为剖分三角网约束边这一特点,通过选择原始多边形一定数量的边,并对这些边构建最优三角形,将原始多边形分割成若干个小的简单多边形,这些简单多边形之间通过三角形进行连接。至此,原始多边形的三角剖分直接转化为这些简单多边形的三角剖分,这样由一条边寻找一顶点构建最优三角形,直接在该边所在的简单多边形内进行搜索,大大减少了点的搜索范围,提高了算法效率。利用基于边优先的多边形三角剖分算法对分块后的小多边形进行三角剖分,从而完成整个多边形的三角剖分。算法具有适用性广,剖分三角形网形稳定、最优,思路简单,易于实现,执行效率高的特点,最后通过实验证明了本算法的科学性和先进性。 相似文献
12.
《制图学和地理信息科学》2013,40(2):153-164
The analysis of dynamic spatial systems requires an explicit spatio-temporal data model and spatio-temporal analysis tools. Event-based models have been developed to analyze discrete change in continuous and feature-based spatial data. In this paper, a spatio-temporal graph model is described that supports the analysis of continuous change in feature-based polygon spatial data. The spatio-temporal graph edges, called temporal links, track changes in polygon topology through space and time. The model also introduces the concept of a spatial-interaction region that extends a model's focus beyond short-term local events to encompass long-term regional events. The structure of the spatio-temporal graph is used to classify these events into five types of local polygon events and two types of spatial-interaction region events. To illustrate its utility, the model is applied to the ecological question of how patch size influences longevity in underwater plant communities in Chesapeake Bay, USA. Both a short-term local analysis and a longer-term regional analysis showed that patches of plants, or groups of patches, larger than one to two hectares in size were more likely to persist than smaller patches or groups of patches. Overall, the spatio-temporal graph model approach appears applicable to a variety of spatio-temporal questions. 相似文献
13.
D. A. Smith 《Journal of Geodesy》2002,76(3):150-168
A new method for computing gravitational potential and attraction induced by distant, global masses on a global scale has
been developed. The method uses series expansions and the well known one-dimensional fast Fourier transform (1-D FFT) method.
It has been proven to be significantly faster than quadrature while being equally accurate. Various quantities were studied
to cover the two primary applications of the Stokes–Helmert scheme of modeling effects. These two applications (or paths),
given the names R/r/D and R/D/r, are briefly discussed, although the primary objective of the paper is to provide computational
information to either path, rather than choosing one path as preferable to the other. It is further shown that the impact
of masses outside a 4-degree cap can impact the absolute computation of the geoid at more than 1 cm, and should therefore
be included in all local geoid computations seeking that accuracy.
Received: 13 December 2000 / Accepted: 3 September 2001 相似文献
14.
Pattern based map comparisons 总被引：5，自引：0，他引：5
Roger White 《Journal of Geographical Systems》2006,8(2):145-164
Map comparison techniques based on a pixel-by-pixel comparison are useful for many purposes, but fail to reveal important aspects of map similarities and differences. In contrast, pattern based map comparison techniques address the question of structural similarity, although with these approaches the comparison problem becomes open ended, since there is an unlimited number of ways to characterise a pattern. Two types of pattern based technique are used here to analyse the test sets of maps. The first, a fuzzy polygon based matching technique, focuses on the meso-scale aspects of pattern. It is based on the areal intersection of land use polygons on the two maps being compared. The areal intersection, areal complement, and polygon size values are fuzzified into an appropriate set of categories, a set of fuzzy inference rules is applied to derive memberships in local matching categories, and finally the local matching category memberships are defuzzified to yield local matching values for each land use polygon on the reference map. The second approach, fractal analysis, captures macro-scale or global qualities of the maps. Two measures are calculated here: the radial dimension and the cluster size—frequency dimension. The polygon matching approach provides only limited insight when applied to the case of the map set representing differences in classification. It proves much more effective when applied to the problem of change detection, revealing areas where the pattern has changed and giving local measures of the degree of change. The approach is particularly useful in the case where there is a considerable degree of random change at the pixel level, as changes in the underlying pattern are extracted from the noise, while pixel based approaches largely detect the noise. 相似文献
15.
An integrated representation of spatial and temporal relationships between evolving regions 总被引：7，自引：0，他引：7
The study of relationships between evolving regions within GIS still needs the development of operators that integrate the
spatial and temporal dimensions. This paper introduces a new approach that combines topological relationships between regions
in 2-dimensional space with temporal relationships between convex intervals in time. Resulting relationships are defined and
visually presented within a 3-dimensional space that integrates the geographical space as a 2-dimensional space and the time
line as the third dimension. Conceptual neighbourhoods are identified and extended by the concept of semi-transitions and
transitions. Such a flexible framework presents the advantage of being derived from accepted relationships in both space and
time. Its computational implementation is therefore compatible with current spatial and temporal GIS models.
Received: May 2000 / Accepted: June 2001 相似文献
16.
Jean H.P. Paelinck 《Journal of Geographical Systems》2002,4(4):371-383
Links between socio-economic units have been studied by means of various techniques. This study analyses networks that take
on a permanently growing importance in evolutionary economics. The analysis is conducted in a sequential way on matrices picturing
the intensities of certain relations; the technique used is linear assignment. The latter is first applied to matrices of
socio-economic relations set up for the Netherlands and Portugal; the various types of “networking” present could be revealed
and compared. Medical activities, taken in their socio-economic setting, rest also on various networks ; available matrices
for the Netherlands are submitted to the above method of analysis. Moreover, a classical input-output matrix for the United
Kingdom is used as a last test for the validity of the method.
Received: 1 March 2002 / Accepted: 19 November 2002 相似文献
17.
The recovery of a full set of gravity field parameters from satellite gravity gradiometry (SGG) is a huge numerical and computational
task. In practice, parallel computing has to be applied to estimate the more than 90 000 harmonic coefficients parameterizing
the Earth's gravity field up to a maximum spherical harmonic degree of 300. Three independent solution strategies (preconditioned
conjugate gradient method, semi-analytic approach, and distributed non-approximative adjustment), which are based on different
concepts, are assessed and compared both theoretically and on the basis of a realistic-as-possible numerical simulation regarding
the accuracy of the results, as well as the computational effort. Special concern is given to the correct treatment of the
coloured noise characteristics of the gradiometer. The numerical simulations show that the three methods deliver nearly identical
results—even in the case of large data gaps in the observation time series. The newly proposed distributed non-approximative
adjustment approach, which is the only one of the three methods that solves the inverse problem in a strict sense, also turns
out to be a feasible method for practical applications.
Received: 17 December 2001 / Accepted: 17 July 2002
Acknowledgments. We would like to thank Prof. W.-D. Schuh, Institute of Theoretical Geodesy, University of Bonn, for providing us with the
serial version of the PCGMA algorithm, which forms the basis for the parallel PCGMA package developed at our institute. This
study was partially performed in the course of the GOCE project `From E?tv?s to mGal+', funded by the European Space Agency
(ESA) under contract No. 14287/00/NL/DC.
Correspondence to: R. Pail 相似文献
18.
A rule-based model for managing uncertainty in spatial databases is presented. The overall goal of the model is to allow
a user to assign to a single map class each polygon whose class is not entirely certain using more information than only the
map class attributes of such polygons (that are herein termed abjects). This situation might arise when multiple map realizations of an area are available and interpreters/cartographers are not
in agreement as to what class is present at a given location or when a digital image is classified by algorithmic/probabilistic
means. The scale-based model developed relies on attribute, geometric, and neighborhood measures of abjects arranged in a hierarchical rule-based structure. Structural knowledge of these measures leads to the procedural knowledge
that determines what action – e.g., merge, reclassify, retain – is to be taken for a given abject. The wider applicability of the model and associated methodology is also discussed.
Received: 5 July 2001 / Accepted: 11 April 2002 相似文献
19.
20.
Tide gauge records of Hong Kong covering the past 45 years (1954.0–1999.0) are adopted to analyze the basic features of sea
level changes in the region. Data sets of atmospheric pressure, southern oscillation index and sea surface temperature during
the same time span are also used to determine the possible link between the sea level changes in Hong Kong and local and global
geophysical processes. Results indicate that the sea level of Hong Kong has a rising trend of 1.9 ± 0.4 mm per year, and that
there is an upward offset of about 15 cm in the pre-1957.0 tide gauge records. The effect of local atmospheric pressure variations
on the amplitude of the annual sea level change is about 30% of the amplitude that is calculated after the effect is corrected.
It is also found that the interannual variations in the sea level of Hong Kong are related to El Ni?o and La Ni?a events that
happen frequently in the tropical Pacific.
Received: 27 October 1999 / Accepted: 15 August 2000 相似文献