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61.
This study developed an analytical procedure based upon a spectral unmixing model for characterizing and quantifying urban landscape changes in Indianapolis, Indiana, the United States, and for examining the environmental impact of such changes on land surface temperatures (LST). Three dates of Landsat TM/ETM+ images, acquired in 1991, 1995, and 2000, respectively, were utilized to document the historical morphological changes in impervious surface and vegetation coverage and to analyze the relationship between these changes and those occurred in LST. Three fraction endmembers, i.e., impervious surface, green vegetation, and shade, were derived with an unconstrained least-squares solution. A hybrid classification procedure, which combined maximum-likelihood and decision-tree algorithms, was developed to classify the fraction images into land use and land cover classes. Correlation analyses were conducted to investigate the changing relationships of LST with impervious surface and vegetation coverage. Results indicate that multi-temporal fraction images were effective for quantifying the dynamics of urban morphology and for deriving a reliable measurement of environmental variables such as vegetation abundance and impervious surface coverage. Urbanization created an evolved inverse relationship between impervious and vegetation coverage, and brought about new LST patterns because of LST's correlations with both impervious and vegetation coverage. Further researches should be directed to refine spectral mixture modeling by stratification, and by the use of multiple endmembers and hyperspectral imagery. 相似文献
62.
Christoph Förste Roland Schmidt Richard Stubenvoll Frank Flechtner Ulrich Meyer Rolf König Hans Neumayer Richard Biancale Jean-Michel Lemoine Sean Bruinsma Sylvain Loyer Franz Barthelmes Saskia Esselborn 《Journal of Geodesy》2008,82(6):331-346
The recent improvements in the Gravity Recovery And Climate Experiment (GRACE) tracking data processing at GeoForschungsZentrum
Potsdam (GFZ) and Groupe de Recherche de Géodésie Spatiale (GRGS) Toulouse, the availability of newer surface gravity data
sets in the Arctic, Antarctica and North-America, and the availability of a new mean sea surface height model from altimetry
processing at GFZ gave rise to the generation of two new global gravity field models. The first, EIGEN-GL04S1, a satellite-only
model complete to degree and order 150 in terms of spherical harmonics, was derived by combination of the latest GFZ Potsdam
GRACE-only (EIGEN-GRACE04S) and GRGS Toulouse GRACE/LAGEOS (EIGEN-GL04S) mean field solutions. The second, EIGEN-GL04S1 was
combined with surface gravity data from altimetry over the oceans and gravimetry over the continents to derive a new high-resolution
global gravity field model called EIGEN-GL04C. This model is complete to degree and order 360 and thus resolves geoid and
gravity anomalies at half- wavelengths of 55 km at the equator. A degree-dependent combination method has been applied in
order to preserve the high accuracy from the GRACE satellite data in the lower frequency band of the geopotential and to form
a smooth transition to the high-frequency information coming from the surface data. Compared to pre-CHAMP global high-resolution
models, the accuracy was improved at a spatial resolution of 200 km (half-wavelength) by one order of magnitude to 3 cm in
terms of geoid heights. The accuracy of this model (i.e. the commission error) at its full spatial resolution is estimated
to be 15 cm. The model shows a reduced artificial meridional striping and an increased correlation of EIGEN-GL04C-derived
geostrophic meridional currents with World Ocean Atlas 2001 (WOA01) data. These improvements have led to select EIGEN-GL04C
for JASON-1 satellite altimeter data reprocessing.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
63.
Yanming Feng 《Journal of Geodesy》2008,82(12):847-862
This paper presents a general modeling strategy for ambiguity resolution (AR) and position estimation (PE) using three or
more phase-based ranging signals from a global navigation satellite system (GNSS). The proposed strategy will identify three
best “virtual” signals to allow for more reliable AR under certain observational conditions characterized by ionospheric and
tropospheric delay variability, level of phase noise and orbit accuracy. The selected virtual signals suffer from minimal
or relatively low ionospheric effects, and thus are known as ionosphere-reduced virtual signals. As a result, the ionospheric parameters in the geometry-based observational models can be eliminated for
long baselines, typically those of length tens to hundreds of kilometres. The proposed modeling comprises three major steps.
Step 1 is the geometry-free determination of the extra-widelane (EWL) formed between the two closest L-band carrier measurements,
directly from the two corresponding code measurements. Step 2 forms the second EWL signal and resolves the integer ambiguity
with a geometry-based estimator alone or together with the first EWL. This is followed by a procedure to correct for the first-order
ionospheric delay using the two ambiguity-fixed widelane (WL) signals derived from the integer-fixed EWL signals. Step 3 finds
an independent narrow-lane (NL) signal, which is used together with a refined WL to resolve NL ambiguity with geometry-based
integer estimation and search algorithms. As a result, the above two AR processes performed with WL/NL and EWL/WL signals
respectively, either in sequence or in parallel, can support real time kinematic (RTK) positioning over baselines of tens
to hundreds of kilometres, thus enabling centimetre-to-decimentre positioning at the local, regional and even global scales
in the future. 相似文献
64.
天津市地下水开采对地面沉降影响的多元回归分析 总被引:1,自引:0,他引:1
地下水的过量开采是天津市引起地面沉降的主要原因。因此天津市提出了“压缩地下水开采量”、“地下水人工回灌”、“调整地下水开采层次”等控制地面沉降的3大技术措施。经过多年的努力,控制地面沉降效果明显。如何解决地下水开发与控制地面沉降的关系,更好的贯彻这3大技术措施,是该文编写的初衷。即在开采同样地下水量的情况下,如何使地面沉降量最小;或在地面沉降量容许的情况下,如何开采最大量的地下水。压缩地下水开采量是治理地面沉降的根本措施,亦即如何压缩采水量或调整开采层次会达到最好效果。论文对天津市某区各个地下水开采层的多年累计开采量、累计沉降量进行数据统计分析,建立了该地区累计沉降量及各个地下水开采层的多元相关方程。在此基础上,分析了各个地下水开采层对地面沉降影响的相关程度。以此为该区控制地面沉降的提供依据。 相似文献
65.
Low multipath antennas for GNSS-based attitude determination systems applied to high-altitude platforms 总被引:1,自引:1,他引:0
Luigi Boccia Pasquale Pace Giandomenico Amendola Giuseppe Di Massa 《GPS Solutions》2008,12(3):163-171
High-altitude platforms (HAPs) are a flexible and attractive technology for providing innovative wireless services. These
aerial platforms can be successfully employed for mobile or broadband communications and for disaster monitoring or response.
However, one of the open issues is whether HAP stations can provide reliable services without temporal outages owing to stratospheric
winds that can cause positional and attitude instabilities thus affecting the communication system operation. To counteract
this issue, one possible solution is to use reconfigurable antennas whose pointing direction can be adjusted depending on
the platform spatial orientation. However, this would require real-time three-axial attitude data. As a possible solution,
this paper will review the potential of GNSS-based attitude determination systems with reference to HAP stations. In particular,
it will be shown how the use of a particular class of low multipath and lightweight antennas can provide a high degree of
accuracy without altering the avionic ballast. 相似文献
66.
Agricultural Census data is summarised over spatially coarse reporting units for reasons of farm confidentiality. This is problematic for research at a local level. This article describes an approach combining dasymetric and volume preserving techniques to create a national land use dataset at 1 km2 resolution. The results for an English county are compared with contemporaneous aggregated habitat data. The results show that the accurate estimates of local agricultural land use (Arable and Grass) patterns can be estimated when individual 1 km squares are combined into blocks of > 9 squares, thereby providing local estimates of agricultural land use. This in turn allows more detailed modelling of land uses related to specific livestock and cropping activities. The dataset created by this work has been subject to extensive external validation through its incorporation into a number of other national models: nitrate leaching (e.g. MAGPIE, NEAP‐N), waste, and pathogen modelling related to agricultural activity. 相似文献
67.
国土资源网格化管理与服务系统的设计与实现 总被引:3,自引:0,他引:3
从地学网格的基本概念出发,提出了由网络层、数据层与应用层以及安全保障和标准化体系构成的国土资源管理与服务系统总体框架。探索了国土资源网格化管理的运行模式,明确了不同角色在网格化管理中的职责。对于网格化管理中的数据更新机制、更新流程和更新方式进行了详细的探讨。最后,文章结合东莞市的实际设计并实现了国土资源网格化管理与服务系统原型。 相似文献
68.
69.
土地资源具有稀缺性和不可再生性,土地供给日渐紧张,拓展土地利用空间、将土地利用由平面趋向立体化发展的趋势日渐成熟。青岛市崂山区将建设用地使用权分层出让,不但垂范了法规政策,对区域经济的发展也具有很大的现实意义。 相似文献
70.
以烟台市为例,从生态环境协调性、经济可行性、社会可接受性等方面,构建了2004年城市土地可持续利用评价的指标体系,采用特尔斐等方法计算了其可持续利用度。结果表明,烟台城市土地利用目前仍处于可持续利用起步阶段。 相似文献