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241.
Ross S. Lunetta Yang Shao Jayantha Ediriwickrema John G. Lyon 《International Journal of Applied Earth Observation and Geoinformation》2010
The Moderate Resolution Imaging Spectrometer (MODIS) Normalized Difference Vegetation Index (NDVI) 16-day composite data product (MOD12Q) was used to develop annual cropland and crop-specific map products (corn, soybeans, and wheat) for the Laurentian Great Lakes Basin (GLB). The crop area distributions and changes in crop rotations were characterized by comparing annual crop map products for 2005, 2006, and 2007. The total acreages for corn and soybeans were relatively balanced for calendar years 2005 (31,462 km2 and 31,283 km2, respectively) and 2006 (30,766 km2 and 30,972 km2, respectively). Conversely, corn acreage increased approximately 21% from 2006 to 2007, while soybean and wheat acreage decreased approximately 9% and 21%, respectively. Two-year crop rotational change analyses were conducted for the 2005–2006 and 2006–2007 time periods. The large increase in corn acreages for 2007 introduced crop rotation changes across the GLB. Compared to 2005–2006, crop rotation patterns for 2006–2007 resulted in increased corn–corn, soybean–corn, and wheat–corn rotations. The increased corn acreages could have potential negative impacts on nutrient loadings, pesticide exposures, and sediment-mediated habitat degradation. Increased in US corn acreages in 2007 were related to new biofuel mandates, while Canadian increases were attributed to higher world-wide corn prices. Additional study is needed to determine the potential impacts of increases in corn-based ethanol agricultural production on watershed ecosystems and receiving waters. 相似文献
242.
This study assesses surface urban heat island (UHI) and its associated surface physical characteristics using remote sensing approaches. TERRA/MODIS images acquired in 2005 in three different seasons were selected to generate land surface tem-perature and surface characteristics for the Changsha-Zhuzhou-Xiangtan metropolitan area in China. The intensity of urban heat is-land effects and its seasonal variations were examined. The result showed that UHI effects were significant both in the summer and the spri... 相似文献
243.
Kinematic precise point positioning at remote marine platforms 总被引:6,自引:2,他引:6
Precise kinematic differential positioning using the global positioning system (GPS) at a marine platform usually requires
a relatively short distance (e.g. <500 km) to a land-based reference station. As an alternative, precise point positioning
(PPP) is normally considered free from this limiting requirement. However, due to the prerequisite of network-based satellite
products, PPP at a remote marine platform may still be affected by its distance to the reference network. Hence, this paper
investigates this scenario by configuring rings of reference stations with different radii centered on a to-be-positioned
marine platform. Particularly, we applied ambiguity resolution at a single station to PPP by estimating uncalibrated phase
delays (UPDs). We used three rings of reference stations centered on a vessel, with radii of roughly 900, 2,000 and 3,600 km,
to determine satellite clocks and UPDs independently. For comparison, we also performed differential positioning based on
a single reference station with baseline lengths of about 400, 1,700 and 2,800 km. We demonstrate that, despite the increasing
ring-network radius to a few 1,000 km, the overall change in accuracy of the satellite clocks that are used at the vessel
is smaller than 0.02 ns, and the RMS values of differences between the three sets of narrow-lane UPD estimates are around
0.05 cycles only. Moreover, the kinematic positioning accuracy of PPP is affected by the increasing ring-network radius, but
can still achieve several centimeters after ambiguity resolution when the vessel is over a few 1,000 km away from the ring
network, showing better performance than that of differential positioning. Therefore, we propose that ambiguity-fixed PPP
can be used at remote marine platforms that support precise oceanographic and geophysical applications in open oceans. 相似文献
244.
F.J. Colomer Mendoza A. Ferrer Gisbert A. Gallardo Izquierdo M.D. Bovea 《Engineering Geology》2009,105(3-4):231-238
Homogeneous earth dams that are waterproofed with geomembranes are a suitable option for storing water and other sorts of liquids, like leachates from landfills. Such dams do not require complicated engineering technical calculations, their cost is usually low and they are not difficult to construct. To ensure the geotechnical safety of the dam, the slopes of the embankment must be correctly designed and constructed. This paper provides a set of nomograms which allow the user to get the safety factor of the slopes immediately. In some cases, it is only necessary to know previously the material classification according to the Unified Soil Classifications System. From this information it can be determined whether the material is appropriate or not. If the material classification is not available, geotechnical data of the material used in the construction of the embankment are needed. Examples of the application of nomograms are presented. Secondly, the paper includes a set of equations to calculate quickly the safety factor of a slope of earth upper than 7.5 m height. 相似文献
245.
246.
Bovolo F. Bruzzone L. Capobianco L. Garzelli A. Marchesi S. Nencini S. 《Geoscience and Remote Sensing Letters, IEEE》2010,7(1):53-57
247.
进一步认识地球、关注地球发展规律, 保护人类共同家园已成为世界各国政府的共识。共同发展地球观测技术, 提高对地观测能力成为新世纪世界各国的共同要求。2003年发起, 2005年由欧盟组织的地球观测部长级峰会上通过了全球综合地球观测系统(Global Earth Observation System of Systems, GEOSS)十年执行计划, 构成了世界范围内地球观测领域国际科技合作的主流。中国地球观测领域呈现出快速发展的趋势, 并提出了该领域的全球性发展战略, 预示着中国将在国际地球观测领域发挥越来越重要的作用。文章介绍了中国地球观测领域发展现状和趋势, 在分析中国参与全球地球观测领域国际合作现状及目前存在问题的基础上, 提出进一步促进中国参与该领域国际合作, 为中国乃至国际社会发展做出重要贡献的建议。 相似文献
248.
Automated GPS Data Analysis Service 总被引:4,自引:1,他引:4
James F. Zumberge 《GPS Solutions》1999,2(3):76-78
Automatic analysis of geodetic-quality GPS data is available with the use of e-mail and ftp (file transfer program) as an
interface to a computer at the Jet Propulsion Laboratory (JPL), where precise transmitter parameters – GPS ephemerides and
clock errors – are computed regularly. The interface is such that e-mail from an external user causes the JPL computer to
fetch the user's data. The computer than analyzes the data, and places the results in an area accessible to the user. An e-mail
to the user gives information on the location of the analysis results, which the user can subsequently fetch. Operations on
the JPL computer are entirely automatic, and require essentially no labor. ? 1999 John Wiley & Sons, Inc. 相似文献
249.
A GPS-Supported Gravity Survey in the Amazon of Ecuador 总被引:1,自引:0,他引:1
Mamadou Balde Jeremy Fishman Carlos L. V. Aiken Mohamed Abdel-Salam Mauricio F. de la Fuente 《GPS Solutions》1999,2(3):3-17
The growing importance and effectiveness of the Global Positioning System (GPS) in positioning geophysical surveys is now
well established. In Ecuador's Amazon basin the use of GPS was the determining factor in the successful completion of a gravity
survey carried out in 1994. Over 500 gravity stations, spaced from 1 to 5 km apart and positioned by GPS, were collected in
the jungle environment in the country's southeast, where the preexisting data, of variable and unknown quality, were mostly
confined to areas along the major rivers. This station densification, which includes the reoccupation of selected points,
contributed to increase the gravity coverage; it also allowed us to evaluate and correct 1100 preexisting data points in the
area, so that the different surveys can be merged. The composite data set is used for a geologic analysis of the study area,
where previously unknown structures are discovered. ? 1999 John Wiley & Sons, Inc. 相似文献
250.
Paul F. McMillan Brent T. Poe Thomas R. Stanton Richard L. Remmele 《Physics and Chemistry of Minerals》1993,19(7):454-459
We have obtained high quality Raman spectra for two H/D isotopically substituted hydrous aluminosilicate glasses with compositions along the NaAlSi3O8-SiO2 join. Consistent with the results of previous studies, the isotope shift for the band near 900 cm–1, whose intensity grows with increasing water content, is extremely small: v
h
/v
d
= 1.004 ± 0.004. The lack of a definite H/D isotope shift for this band does not, however, preclude its association with a vibration of a hydrous species in the glass, because of likely strong coupling between different vibrational modes of hydrated framework species. The 900 cm–1 band could well be due to a T — OH (T = Si, Al) stretching or bending vibration in the hydrous glass, as required by the presence of a combination band near 4500 cm–1 in near-infrared spectra. 相似文献