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1.
An empirical test of the competing destinations model 总被引：2，自引：0，他引：2
It has long been believed that properties of spatial structure have a strong effect on trip distribution, which thus leads
to a bias in the estimated distance decay parameters of spatial interaction models. This paper is an attempt to identify to
what extent the spatial structure effect affects the trip distribution and determine whether the incorporation of a term to
account for the relative location of destinations into the conventional gravity models, results in a model that can more correctly
represent the actual trip distribution. The main focus is on the comparison of the origin–specific estimates of the distance
decay parameter, calibrated from the traditional production-constrained model and the production-constrained competing destinations
model. The results show that the competing destinations model is superior to the conventional model in both reproducing the
interaction flows and giving behavioral explanation to the distance decay parameters, but the essential aim of the competing
destinations model to remove the map pattern from the distance decay parameters of the conventional model has not been identified.
Received: 5 September 2001 / Accepted: 17 June 2002
We are grateful to Gloria. A. Swieczkowski for kindly providing the migration data. The authors also gratefully acknowledge
the comments of the referees. 相似文献
2.
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
3.
C. Jeganathan V. K. Dadhwal Kiran Gupta P. L. N. Raju 《Journal of the Indian Society of Remote Sensing》2009,37(4):539-549
The study compared forest cover maps derived using coarse resolution vegetation continuous fields (MODIS VCF; 500m resolution)
with the maps derived from medium resolution (24m; IRS LISS-III) data. The comparison of VCF, per cent tree cover product,
for the years 2000 to 2004 with LISS III forest density class maps of 2001 and 2003 was carried out for two sites representing
hilly (Uttarakhand) and undulating terrains (Madhya Pradesh). Slicing VCF to corresponding forest crown cover, i.e., 0–10%,
10–40%, 40–70% and >70% produced considerable difference in forest area estimates when compared to original LISS III derived
crown cover area. The corresponding value range in VCF for 0–10% of actual forest cover were 0–31% and 0–25% in 2 sites respectively,
and the respective limit was consistent at 1–20% when VCF range were sliced with respect to upscaled LISS III at 500m resolution.
Similarly, all other class limits were also found through iterative process. These limits were similar, within a site, across
five years. Spatial Kappa match between these two data indicated higher match in 40–70% class, and also in undulating site.
When compared at same resolution, similar forest area cover estimated with weighted area upscaling gave closest match. The
study is useful in knowing the usability and limits of VCF product, and utility of spatial Kappa. 相似文献
4.
This paper analyzes the spatial patterns of households' distribution in clusters of cities and the effects on regional growth
using spatial exploratory techniques and a model of growth that incorporates spatial location. Our empirical analysis shows
that, over the 1980–1990 period, in Southern New England, patterns of spatial clustering of households did create heterogeneous
growth rates in the region. Also, there is evidence that clusters of cities and isolated cities created spillover growth effects
in bordering towns.
Received: 5 September 2001 / Accepted: 2 August 2002 相似文献
5.
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
6.
激光雷达森林参数反演研究进展 总被引：6，自引：0，他引：6
激光雷达通过发射激光能量和接收返回信号的方式,来获取高精度的森林空间结构和林下地形信息。全波形激光雷达通过记录返回信号的全部能量,得到亚米级植被垂直剖面;离散回波激光雷达记录的单个或多个回波,表示来自不同冠层的回波信号。星载激光雷达一般采用全波形或光子计数激光剖面系统,仅能获取卫星轨道下方的单波束或多波束数据,用于区域/全球范围的森林垂直结构及变化观测。机载激光雷达多采用离散回波或全波形激光扫描系统,能够获取飞行轨迹下方特定视场范围内的扫描数据,用于林分/区域范围的森林结构观测。地基激光雷达多采用离散回波激光扫描系统,获取以测站为中心的球形空间内扫描数据,用于单木/样地范围的森林结构观测。激光雷达单木因子估测方法可分为CHM单木法、NPC单木法和体元单木法3类。CHM单木法通过局部最大值识别树冠顶点,采用区域生长或图像分割算法识别树冠边界或树冠主方向,NPC单木法一般通过空间聚类或形态学算法识别单木,体元单木法在3维体元空间采用区域生长或空间聚类算法识别树冠。根据激光雷达冠层高度分布可以估测林分因子,冠层高度分布特征来自于离散点云或全波形。多时相激光雷达可用于森林生长量、生物量变化等监测,以及森林采伐、灾害等引起的结构变化监测。随着激光雷达技术的发展,它将在森林调查、生态环境建模等生产与科学研究领域中得到更为广泛的应用。 相似文献
7.
8.
Arun K. Thakur Gajendra Singh Sarnam Singh G. S. Rawat 《Journal of the Indian Society of Remote Sensing》2011,39(1):127-134
The study reports the impact of migratory livestock in the buffer area of Kedarnath Wildlife Sanctuary. The cumulative impacts
of livestock grazing, fuel wood extraction and other anthropogenic pressures on forest cover in and around camping sites have
been analyzed using satellite data and field observations. Multi-date satellite data were used to map the forest cover around
16 seasonal livestock camps. An annual loss of about 7.25 ha of forest covers during 1976–1990, 13.57 ha during 1990–1999
and 11.46 ha during 1999–2005 are recorded. A loss of 108.53 ha of forestland has been estimated during 1976–1990, about 122.16 ha
during 1990–1999 and 68.78 ha during 1999–2005. It is also observed that many of the isolated camping sites are now connected
due to loss of vegetation. Phytosociological analysis indicates that the number of seedlings and saplings in three species
of Quercus (Q. leucotrichophora, Q. floribunda and Q. semecarpifolia) as compared to mature tress is very less around cattle camping sites. The ratio of number of sapling with seedling and trees
indicates that the status of sapling is nil to very poor, an indication of loss of saplings due to either trampling or grazing. 相似文献
9.
A. V. Suresh Babu V. Venkateshwar Rao I. V. Muralikrishna 《Journal of the Indian Society of Remote Sensing》2007,35(1):81-91
Water Utilisation Index (WUI) defined as area irrigated per unit volume is a measure of water delivery performance and constitutes
one of the important spatial performance indicators of an irrigation system. WUI also forms basis for evaluating the adequacy
of seasonal irrigation supplies in an irrigation system (inverse of WUI is delta, i.e. depth of water supplied to a given
irrigation unit). In the present study WUI and adequacy indicators were used in benchmarking the performance of Nagarjunasagar
Left Canal Command (NSLC) in Andhra Pradesh. Optimised temporal satellite data of rabi season during the years 1990–91 and
1998–99 was used in deriving irrigated crop areas adopting hierarchical classification approach. Paddy is the predominant
crop grown and cotton, chillies, sugarcane etc. are the other crops grown in the study area. Equivalent wet area (paddy crop
area) was estimated using the operationally used project specific conversion factors. WUI was estimated at disaggregated level
viz., distributary, irrigation block, irrigation zone level using the canal discharge data. At project level, WUI estimated
to be 65 ha/MCM and 92 ha/MCM during rabi season of 1990–91 and 1998–99 years respectively. A comparison of total irrigated
area and discharges corresponding to both the years indicate that irrigation service is extensive and sub optimal during 1998–99
and it is intensive and optimal in 1990–91. It was also observed that WUI is lesser in blocks of with higher Culturable Command
Area (CCA) compared to the blocks of lower CCA. All the disaggregated units were ranked into various groups of different levels
of water distribution performance. The study demonstrates the utility of WUI as spatial performance indicator and thus useful
for benchmarking studies of irrigation command areas. The WUI together with satellite data derived spatial irrigation intensity,
crop productivity constitutes important benchmarking indices in irrigation command areas. 相似文献
10.
Associate Professor Bruce Foster 《国际地球制图》2013,28(4):55-56
Abstract Three spatial resolutions of airborne remote sensing imagery (60 cm, 1 m, and 2 m) collected over multi‐layer aspen, pine, spruce, and mixedwood forest stands in Alberta on July 18th, 1998 were tested for their ability to provide a statistical stand discrimination based on spatial co‐occurrence texture analysis. As spatial resolution increased, classification accuracies increased. The highest classification accuracy of 86.7% was obtained using the highest image spatial resolution data (60 cm), with spatial co‐occurrence texture and spectral signatures combined, and a thirteen‐class multi‐layer stand stratification. The texture of the highest spatial resolution imagery (60 cm pixel resolution) was interpreted to contain information on the crown architecture of individual trees. In larger windows, the texture was interpreted to contain information on stand structure. Texture of lower spatial resolution imagery (1 m and 2 m pixel resolution) could not detect individual tree crown architecture and was determined to be related primarily to stand structure characteristics. The use of texture channels improved the per‐plot classification accuracies by 15.7%, compared to the use of the spectral data alone. 相似文献
11.
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
12.
Geostatistical incorporation of spatial coordinates into supervised classification of hyperspectral data 总被引：1，自引：0，他引：1
P. Goovaerts 《Journal of Geographical Systems》2002,4(1):99-111
This paper presents a methodology to incorporate both hyperspectral properties and spatial coordinates of pixels in maximum
likelihood classification. Indicator kriging of ground data is used to estimate, for each pixel, the prior probabilities of
occurrence of classes which are then combined with spectral-based probabilities within a Bayesian framework. In the case study
(mapping of in-stream habitats), accounting for spatial coordinates increases the overall producer's accuracy from 85.8% to
93.8%, while the Kappa statistic rises from 0.74 to 0.88. Best results are obtained using only indicator kriging-based probabilities,
with a stunning overall accuracy of 97.2%. Significant improvements are observed for environmentally important units, such
as pools (Kappa: 0.17 to 0.74) and eddy drop zones (Kappa: 0.65 to 0.87). The lack of benefit of using hyperspectral information
in the present study can be explained by the dense network of ground observations and the high spatial continuity of field
classification which might be spurious.
Received: 12 April 2001 / Accepted: 7 September 2001 相似文献
13.
Apropos laser tracking to GPS satellites 总被引：3，自引：0，他引：3
. Laser tracking to GPS satellites (PRN5 and 6) provides an opportunity to compare GPS and laser systems directly and to combine
data of both in a single solution. A few examples of this are given in this study. The most important results of the analysis
are that (1) daily SLR station coordinate solutions could be generated with a few cm accuracy; (2) coordinates of nine stations
were determined in a 2.3-year-long arc solution; (3) the contribution of laser data on the `SLR-GPS' combined orbit, resulting
from the simultaneous processing of SLR and GPS data, is significant and (4) laser-only orbits have an accuracy of 10–20 cm,
1-day predictions of SLR orbits differ from IGS orbits by about 20–40 cm, 2-day predictions by 50–60 cm.
Received: 1 October 1996 / Accepted: 14 February 1997 相似文献
14.
Land-use change and Land-cover classes in Garur Ganga watershed of Bageshwar district in Uttranchal State during the periods 1963–1996 and 1986–1996 were analyzed through Survey of India Topographical Sheet and visual interpretation of LANDSAT 5 TM image bands 2, 3 and 4 using Geographical Information System (GIS). The detailed analysis have revealed that the area under agriculture and settlement increased from 34.98 to 42.34%. whereas the forest and barren land show a declining trend. Expansion of agriculture land and builtup areas have been found to be maximum in the 1200–1600 m elevation zone with 7–14° slope class. The loss of vegetation cover has been estimated to be 5.07% between 1963-1996 and 0.81% between 1986–1996. 相似文献
15.
Ola Hall Geoffrey J. Hay 《International Journal of Applied Earth Observation and Geoinformation》2003,4(4):311-327
Landscape spatial pattern is dependent not only on interacting physiographic and physiological processes, but also on the temporal and spatial scales at which the resulting patterns are assessed. To detect significant spatial changes occurring through space and time three fundamental components are required. First, a multiscale dataset must be generated. Second, a change detection framework must be applied to the multiscale dataset. Third, a procedure must be developed to delineate individual image-objects and identify them as they change through scale. In this paper, we introduce an object-specific multiscale digital change detection approach. This approach incorporates multitemporal SPOT Panchromatic (Pan) data, object-specific analysis (OSA), object-specific up-scaling (OSU), marker-controlled watershed segmentation (MCS) and image differencing change detection. By applying this framework to SPOT Pan data, image-objects that have changed between registration dates can be identified and delineated at their characteristic scale of expression. Results illustrate that this approach has the ability to automatically detect changes at multiple scales as well as suppress sensor related noise. This study was conducted in the forest region of the Örebro Administrative Province, Sweden. 相似文献
16.
Daniel A. Griffith 《Journal of Geographical Systems》2002,4(1):43-51
As either the spatial resolution or the spatial scale for a geographic landscape increases, both latent spatial dependence
and spatial heterogeneity also will tend to increase. In addition, the amount of georeferenced data that results becomes massively
large. These features of high spatial resolution hyperspectral data present several impediments to conducting a spatial statistical
analysis of such data. Foremost is the requirement of popular spatial autoregressive models to compute eigenvalues for a row-standardized
geographic weights matrix that depicts the geographic configuration of an image's pixels. A second drawback arises from a
need to account for increased spatial heterogeneity. And a third concern stems from the usefulness of marrying geostatistical
and spatial autoregressive models in order to employ their combined power in a spatial analysis. Research reported in this
paper addresses all three of these topics, proposing successful ways to prevent them from hindering a spatial statistical
analysis. For illustrative purposes, the proposed techniques are employed in a spatial analysis of a high spatial resolution
hyperspectral image collected during research on riparian habitats in the Yellowstone ecosystem.
Received: 25 February 2001 / Accepted: 2 August 2001 相似文献
17.
Misspecifications in interaction model distance decay relations: A spatial structure effect 总被引：1，自引：0，他引：1
M. Tiefelsdorf 《Journal of Geographical Systems》2003,5(1):25-50
An exclusively statistical approach is proposed to address the spatial structure effects of general interaction models. It is shown that the spatial heterogeneity in the estimated region-specific distance decay
parameters may in part be due to the combination of two factors: (a) a functional mis-specification of the global distance
decay relationship; and (b) the heterogeneity in the region-specific conditional distance distributions. A properly specified
global distance decay function allows controlling for these spatially induced biases in the local distance decay parameters.
However, inherent multicollinearities between the set of region specific distance decay parameters and other estimated model
parameters prevent an unambiguous interpretation. A key conclusion is that a proper model specification, in particular, the
specification of the global distance decay relationship, is of paramount importance in interaction modeling and for accessibility
studies.
Received: September 2002 / Accepted: January 2003 相似文献
18.
Forest plantations are an important source of terrestrial carbon sequestration. The forest of Robinia pseudoacacia in the Yellow River Delta (YRD) is the largest artificial ecological protection forest in China. However, more than half of the forest has appeared different degrees of dieback and even death since the 1990s. Timely and accurate estimation of the forest aboveground biomass (AGB) is a basis for studying the carbon cycle of forests. Light Detecting and Ranging (LiDAR) has been proved to be one of the most powerful methods for forest biomass estimation. However, because of an irregular and overlapping shape of the broadleaved forest canopy in a growing season, it is difficult to segment individual trees and estimate the tree biomass from airborne LiDAR data. In this study, a new method was proposed to solve this problem of individual tree detection in the Robinia pseudoacacia forest based on a combination of the Unmanned Aerial Vehicle-Light Detecting and Ranging (UAV-LiDAR) with the Backpack-LiDAR. The proposed method mainly consists of following steps: (i) at a plot level, trees in the UAV-LiDAR data were detected by seed points obtained by an individual tree segmentation (ITS) method from the Backpack-LiDAR data; (ii) height and diameter at breast height (DBH) of an individual tree would be extracted from UAV and Backpack LiDAR data, respectively; (iii) the individual tree AGB would be calculated through an allometric equation and the forest AGB at the plot level was accumulated; and (iv) the plot-level forest AGB was taken as a dependent variable, and various metrics extracted from UAV-LiDAR point cloud data as independent variables to estimate forest AGB distribution in the study area by using both multiple linear regression (MLR) and random forest (RF) models. The results demonstrate that: (1) the seed points extracted from Backpack-LiDAR could significantly improve the overall accuracy of individual tree detection (F = 0.99), and thus increase the forest AGB estimation accuracy; (2) compared with MLR model, the RF model led to a higher estimation accuracy (p < 0.05); and (3) LiDAR intensity information selected by both MLR and RF models and laser penetration rate (LP) played an important role in estimating healthy forest AGB. 相似文献
19.
YOU Hongjian LIU Shaochuang LI Shukai 《地球空间信息科学学报》2001,4(3):62-67
1 ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｍｏｔｅｓｅｎｓｉｎｇｈａｓｂｅｅｎａｐｐｌｉｅｄｉｎｍａｎｙｆｉｅｌｄｓｉｎｔｈｅｐａｓｔｄｅｃａｄｅｓ ,ｂｕｔｔｈｅｍｏｄｅｔｏａｃｑｕｉｒｅａｎｄｐｒｏ ｃｅｓｓｔｈｅｒｅｍｏｔｅｓｅｎｓｉｎｇｄａｔａｄｏｅｓｎｏｔｃｈａｎｇｅｒａｄｉ ｃａｌｌｙ .Ｔｈｅｒｅｍｏｔｅｓｅｎｓｉｎｇｉｍａｇｅｍｕｓｔｂｅｇｅｏ＿ｒｅｆｅｒ ｅｎｃｅｄｔｈｒｏｕｇｈｏｎｇｒｏｕｎｄｃｏｎｔｒｏｌｐｏｉｎｔｓ (ＧＣＰｓ) ,ａｎｄｓｔｅｒｅｏｍａｔｃｈｉｎｇｍｕｓｔｂｅａｐｐｌｉｅｄｉ… 相似文献
20.
Yoshiaki Ohsawa Hirofumi Kagaya Takeshi Koshizuka 《Journal of Geographical Systems》2002,4(3):325-342
When demand points are given as a planar map where projection method is explicitly stated, we usually know the latitudes
and longitudes of these points from the map. Then we can solve the Weber problem on the globe, and we do not suffer from errors.
This paper analyses how cylindrical projections cause distortion in the Weber problem when demands are distributed on the
Northern Hemisphere. First, we demonstrate that planar solutions are always located south of the spherical solution if the
Mercator projection, the equirectangular projections with standard parallels near the demands, or the equal-area projection
with the same characteristic is chosen. Second, we verify that this geographical tendency is inclined to hold when the demand
points, are distributed symmetrically, widely or toward the north.
Received: 15 August 2001 / Accepted: 20 April 2002
This paper was partially written while the first author was visiting the Department of Geography at the Catholic University
of Louvain, Louvain-la-Neuve, Belgium [1993–1994]. He is grateful for the hospitality of this department. An earlier version
of this paper was presented in 1994 at the Seventh Meeting of the European Operational Research Working Group on Locational
Analysis in Brussels, and in 1996 at the Fifth World Congress of the Regional Science Association International in Tokyo.
The authors would also like to thank the participants as well as three anonymous referees for their constructive comments. 相似文献