Current researches based on areal or spaceborne stereo images with very high resolutions(<1 m)have demonstrated that it is possible to derive vegetation height from stereo images.The second version of the Advanced ...Current researches based on areal or spaceborne stereo images with very high resolutions(<1 m)have demonstrated that it is possible to derive vegetation height from stereo images.The second version of the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM)is the state-of-the-art global elevation data-set developed by stereo images.However,the resolution of ASTER stereo images(15 m)is much coarser than areal stereo images,and the ASTER GDEM is compiled products from stereo images acquired over 10 years.The forest disturbances as well as forest growth are inevitable in 10 years time span.In this study,the features of ASTER GDEM over vegetated areas under both flat and mountainous conditions were investigated by comparisons with lidar data.The factors possibly affecting the extraction of vegetation canopy height considered include(1)co-registration of DEMs;(2)spatial resolution of digital elevation models(DEMs);(3)spatial vegetation structure;and(4)terrain slope.The results show that the accurate coregistration between ASTER GDEM and national elevation dataset(NED)is necessary over mountainous areas.The correlation between ASTER GDEM minus NED and vegetation canopy height is improved from 0.328 to 0.43 by degrading resolutions from 1 arc-second to 5 arc-second and further improved to 0.6 if only homogenous vegetated areas were considered.展开更多
In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry(eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be rep...In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry(eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is expected to be launched in the mid 2020 s.展开更多
基金This work was partially supported by the National Basic Research Program of China(Grant no.2013CB733404)the National Natural Science Foundation of China(Grant nos.41001208 and 91125003)support for the study was also provided by the NASA Terrestrial Ecology Program(NNX09AG66G).
文摘Current researches based on areal or spaceborne stereo images with very high resolutions(<1 m)have demonstrated that it is possible to derive vegetation height from stereo images.The second version of the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM)is the state-of-the-art global elevation data-set developed by stereo images.However,the resolution of ASTER stereo images(15 m)is much coarser than areal stereo images,and the ASTER GDEM is compiled products from stereo images acquired over 10 years.The forest disturbances as well as forest growth are inevitable in 10 years time span.In this study,the features of ASTER GDEM over vegetated areas under both flat and mountainous conditions were investigated by comparisons with lidar data.The factors possibly affecting the extraction of vegetation canopy height considered include(1)co-registration of DEMs;(2)spatial resolution of digital elevation models(DEMs);(3)spatial vegetation structure;and(4)terrain slope.The results show that the accurate coregistration between ASTER GDEM and national elevation dataset(NED)is necessary over mountainous areas.The correlation between ASTER GDEM minus NED and vegetation canopy height is improved from 0.328 to 0.43 by degrading resolutions from 1 arc-second to 5 arc-second and further improved to 0.6 if only homogenous vegetated areas were considered.
基金support from ERC Starting (Grant No. 639217 CSINEUTRONSTAR)support from a Netherlands Organization for Scientific Research (NWO) Vidi Fellowship+2 种基金suported by the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Global Fellowship (Grant No. 703916)supported in part by the DFG through Grant SFB 1245 and the ERC (Grant No. 307986 STRONGINT)support of the Chinese Academy of Sciences through the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA15020100)
文摘In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry(eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is expected to be launched in the mid 2020 s.
