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331.
The grid DEM(digital elevation model) generation can be from any of a number of sources:for instance,analogue to digital conversion of contour maps followed by application of the TIN model,or direct elevation point modelling via digital photogrammetry applied to airborne images or satellite images.Currently,apart from the deployment of point-clouds from LiDAR data acquisition,the generally favoured approach refers to applications of digital photogrammetry.One of the most important steps in such deployment i... 相似文献
332.
Recently,the expertise accumulated in the field of geovisualization has found application in the visualization of abstract multidimensional data,on the basis of methods called spatialization methods.Spatialization methods aim at visualizing multidimensional data into low-dimensional representational spaces by making use of spatial metaphors and applying dimension reduction techniques.Spatial metaphors are able to provide a metaphoric framework for the visualization of information at different levels of gran... 相似文献
333.
R. Sridhar T. Thangaradjou L. Kannan S. Astalakshmi 《Journal of the Indian Society of Remote Sensing》2010,38(3):565-575
Coastal resources viz., coral reefs, seagrasses, mangroves, and coastal land features viz., sandy beach, mudflats and salt
pan/aquaculture ponds were classified and assessed in the Palk Bay region of the south-east coast of India using IRS LISS
III satellite image (1996, 2000, 2002 and 2004). The study recorded an areal coverage of 286.95 ha of reef area during 2004,
which is 177.54 ha lesser than that of the reef area of 1996. The reef vegetation composed mainly of seaweeds has gained over
29.44 ha during the same period. Likewise, sand over reef area has also increased alarmingly i.e. 120.34 ha between 1996 and
2004. The seagrass beds of Munaikkadu region of the Palk Bay are comparatively protected and have gained over 7.5 ha between
1996 and 2004. It has been found that both the dense (2.99 ha) and sparse (36.45 ha) mangroves have gained their areal coverage
considerably between 1996 and 2004. Whereas in Devipattinam region, many anthropogenic pressures are exerted only on the seagrass
resources which has led to the reduction of over 785.5 ha of dense seagrass beds between 1996 and 2004. The study clearly
indicated that the resources are under the pressures of low to high threats, especially the coral reefs and seagrasses, if
the pressures continue, coastal resources of the Palk Bay may face serious threats of destruction in this part of the Bay
in the years to come. 相似文献
334.
Three methods to correct for the atmospheric propagation delay in very-long-baseline interferometry (VLBI) measurements were
investigated. In the analysis, the NASA R&D experiments from January 1993 to June 1995 were used. The methods were compared
in correcting for the excess propagation delay due to water vapour, the “wet” delay, at one of the sites, the Onsala Space
Observatory on the west coast of Sweden. The three methods were: (1) estimating the wet delay using the VLBI data themselves;
(2) inferring the wet delay from water vapour radiometer (WVR) data, and (3) using independent estimates based on data from
the global positioning system (GPS). Optimum elevation cutoff angles were 22∘ and 26∘ when using WVR and GPS data, respectively. The results were found to be similar in terms of reproducibility of the estimated
baseline lengths. The shortest baselines tend to benefit from external measurements, whereas the lack of improvement in the
longer baselines may be partly due to the large amount of data thrown away when removing observations at low elevation angles.
Over a 2 week period of intensive measurements, the two methods using external data showed an overall improvement, for all
baseline lengths, compared to the first method. This indicates that there are long-term systematic errors in the wet delay
data estimated using WVR and GPS data.
Received: 27 October 1998 / Accepted: 20 May 1999 相似文献
335.
A new approach to GPS ambiguity decorrelation 总被引:12,自引:1,他引:12
Ambiguity decorrelation is a useful technique for rapid integer ambiguity fixing. It plays an important role in the least-squares
ambiguity decorrelation adjustment (Lambda) method. An approach to multi-dimension ambiguity decorrelation is proposed by
the introduction of a new concept: united ambiguity decorrelation. It is found that united ambiguity decorrelation can provide
a rapid and effective route to ambiguity decorrelation. An approach to united ambiguity decorrelation, the HL process, is
described in detail. The HL process performs very well in high-dimension ambiguity decorrelation tests.
Received: 9 March 1998 / Accepted: 1 June 1999 相似文献
336.
Sequestration of large quantities of vitellogenin (VTG) is critical for proper oocyte development in most oviparous vertebrates. While previous studies have shown a general correlation between oocyte growth and the accumulation of various exogenous and endogenous ligands, few studies have attempted to elucidate the role VTG plays in this maternal transfer. In the present study, we have demonstrated that oocytic accumulation of [3H]-2,3,7,8-tetrachlorodibenzo-p-dioxin (3H-TCDD) and [14C]-benzo(a)pyrene (14C-BaP) by gravid Fundulus heteroclitus is directly correlated with oocyte maturational status. A positive correlation was observed between oocyte maturational state (size) and both total quantity (total pmoles) as well as concentration (pmoles/g tissue) of TCDD and BaP. Further, the bi-phasic accumulation of both TCDD and BaP mirrors that previously observed for protein sequestration by cultured Fundulus oocytes. Additionally, both TCDD and BaP were associated with VTG in vivo. HPLC analysis of serum extracts has shown that VTG associates with both parent BaP and BaP metabolites. Studies with 125I-T4 (thyroxine) also suggest that this critical hormone also associates with VTG in vivo. Ongoing studies are examining the VTG-associated transport and oocytic sequestration of 125I-T4 in gravid Fundulus. 相似文献
337.
T. A. Shatilina G. Sh. Tsitsiashvili T. V. Radchenkova 《Russian Meteorology and Hydrology》2010,35(11):740-743
Peculiarities are investigated of the air temperature variation tendencies at some stations of the Far East in 1976–2005.
The estimate of linear trend equation coefficients is computed according to the air temperature observation data using the
least squares method. It is demonstrated that the air temperature trend in northern regions possesses a small probability
at small values of residual variability. In the southern regions, the trend significance increases for almost all seasons
at small values of residual variability. At midlatitude stations, the trend significance in January and February decreases
considerably due to the large values of residual variability. 相似文献
338.
Vasil’ev D. Yu. Vodopyanov V. V. Zayzeva G. S. Zakirzyanov Sh. I. Semenov V. A. Sivokhip Zh. T. Chibilev A. A. 《Doklady Earth Sciences》2019,486(2):724-727
Doklady Earth Sciences - The results of long-term forecasting of the spring runoff in the Belaya River basin based on the water-balance model are presented. The structure and parameters of the... 相似文献
339.
Neolithic culture series in the Yishu River Basin developed in the order of Beixin culture-Dawenkou culture-Longshan culture-Yueshi culture. During the early and middle stage of Longshan culture (4600-4300 cal. yr BP), the climate in the Yishu River Basin was warm and wet. Paddy-oriented agriculture planted paddy was very developed. The society was flourishing with great amount of archaeological sites. The cooling starting in 4200 cal. yr BP made the paddies shortfall in output or even no seeds were gathered. This situation intensified the discrepancy between population and resource. The scarcity in natural resource led to substantial decrease in population and subsequent drop in archaeological sites. About 4000 cal. yr BP Longshan culture was displaced by Yueshi culture which was relatively un- derdeveloped, simple and unsophisticated. 相似文献
340.
Mingchang Wang Xuefeng Niu Qian Yang Shengbo Chen Guodong Yang Fengyan Wang 《Journal of the Indian Society of Remote Sensing》2018,46(1):1-8
Hyper spectral remote sensing is widely used to identify ground objects as a result of the advantages of ground radiation intensity characteristics and spectral position characteristics, in which inversion of vegetation components is the difficult point and hotspot. In this study, Huma county of Heilongjiang Province was selected as the study area, the canopy spectra of four types of typical vegetation were measured in situ firstly, including mongolian oak, cotton grass, lespedeza and white birch. Then, on the basis of analyzing the canopy spectral characteristics and their parameterization, the spectral differences of different vegetations were located, and the parameterization method of characteristics identification was determined. Finally, Hyperion data were used to calculate the canopy albedos based on the bidirectional reflectance model of vegetation canopies, and to map the vegetation components in the study area by use of linear spectral mixture model. The results showed that inversion of vegetation components in high vegetation-covered area was accurate using the canopy albedos and liner spectral mixture model, and was identical with the field sampling, which validated the feasibility of canopy albedos and liner spectral mixture model for the inversion of vegetation components. 相似文献