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991.
992.
S. Fritz M. Massart I. Savin J. Gallego F. Rembold 《International Journal of Applied Earth Observation and Geoinformation》2008,10(4):453
Recent developments in remote sensing technology, in particular improved spatial and temporal resolution, open new possibilities for estimating crop acreage over larger areas. Remotely sensed data allow in some cases the estimation of crop acreage statistics independently of sub-national survey statistics, which are sometimes biased and incomplete. This work focuses on the use of MODIS data acquired in 2001/2002 over the Rostov Oblast in Russia, by the Azov Sea. The region is characterised by large agricultural fields of around 75 ha on average. This paper presents a methodology to estimate crop acreage using the MODIS 16-day composite NDVI product. Particular emphasis is placed on a good quality crop mask and a good quality validation dataset. In order to have a second dataset which can be used for cross-checking the MODIS classification a Landsat ETM time series for four different dates in the season of 2002 was acquired and classified. We attempted to distinguish five different crop types and achieved satisfactory and good results for winter crops. Three hundred and sixty fields were identified to be suitable for the training and validation of the MODIS classification using a maximum likelihood classification. A novel method based on a pure pixel field sampling is introduced. This novel method is compared with the traditional hard classification of mixed pixels and was found to be superior. 相似文献
993.
This paper considers oil-and-gas provinces and the epochs of hydrocarbon generation in Kamchatka. We distinguish the following
epochs of hydrocarbon generation: the Early Mesozoic, the Early Cretaceous, the Late Cretaceous, the Early Paleogene, the
Late Paleogene, the Miocene, and the Pliocene-Quaternary. We emphasize the fact that all gas generation epochs were related
to deep processes, including volcanism and hydrothermal activity. 相似文献
994.
995.
This paper describes a low-cost device for measuring the three-dimensional morphology of a gully headwall. The device was designed to operate in a gully system with the following characteristics: overhanging banks caused by a thick, dense root mat; retreat of the underlying unconsolidated sediments through small slab failures, leading to a considerable variation in retreat rate at each point on the headwall; and changes in the orientation of the headwall owing to changes in sediment properties and the topographical and hydrological controls of gully growth. The device is used to measure a series of closely spaced vertical profiles of the headwall, and the collected data are combined to draw a contour map showing the distance from the plane of the instrument to the headwall. Comparing maps for sequential times enables retreat rates for the diffferent proportions of the headwall to be quantified. 相似文献
996.
A method is developed for scenario prediction of changes in water balance components in northern river basins in the context of possible climate changes. The method uses the land surface model SWAP, describing the heat and mass exchange between the land surface and the atmosphere. Four IPCC climate scenarios, corresponding to specified scenarios of economic, technological, political, and demographic development of the human civilization, were used to forecast different variants of the dynamics of meteorological characteristics in the Northern Dvina River basin in the XXI century, which served as a basis for evaluating possible changes in precipitation, evaporation, and runoff from the Northern Dvina basin until the year of 2063. 相似文献
997.
The dynamics of meteorological elements in the Lena R. Basin is predicted for the XXI century under four IPCC global scenarios of SRES family, corresponding to specified scenarios of the economic, technological, political, and demographic development of the civilization. The obtained predictions are used to simulate variants of possible changes in water balance components in the Lena Basin up to the mid-XXI century. The calculation procedure is based on the use of land-surface model SWAP and a climate scenario generator MAGICC/SCENGEN. 相似文献
998.
The response of multi-degree-of-freedom (MDOF) structures with sliding supports is studied. The problem of sliding structures is a discontinuous one in that different numbers of equations of motion with varying forcing functions are required for the sliding and non-sliding phases. The numerical difficulties involved in this regard in an incremental finite element analysis can be circumvented through the introduction of a fictitious spring for the sliding support. Such a treatment enables one to study the higher mode effects on MDOF sliding structures under the excitation of harmonic or earthquake motions. The dynamic characteristics of MDOF sliding structures will be highlighted in the analysis of a four-storey shear building with sliding support. 相似文献
999.
Tomas?O.?H??kEmail author Edward?S.?Rutherford Shannon?J.?Brines Doran?M.?Mason David?J.?Schwab Michael?J.?McCormick Timothy?J.?DeSorcie 《Estuaries and Coasts》2003,26(1):21-29
The identification and protection of essential habitats for early life stages of fishes are necessary to sustain fish stocks.
Essential fish habitat for early life stages may be defined as areas where fish densities, growth, survival, or production
rates are relatively high. To identify critical habitats for young-of-year (YOY) alewives (Alosa pseud oharengus) in Lake Michigan, we integrated bioenergetics models with GIS (Geographic Information Systems) to generate spatially explicit
estimates of potential population production (an index of habitat quality). These estimates were based upon YOY alewife bioenergetic
growth rate potential and their salmonine predators’ consumptive demand. We compared estimates of potential population production
to YOY alewife yield (an index of habitat importance). Our analysis suggested that during 1994–1995, YOY alewife habitat quality
and yield varied widely throughout Lake Michigan. Spatial patterns of alewife yield were not significantly correlated to habitat
quality. Various mechanisms (e.g., predator migrations, lake circulation patterns, alternative strategies) may preclude YOY
alewives from concentrating in areas of high habitat quality in Lake Michigan. 相似文献
1000.