Backscatter coefficient as an attribute for the classification of full-waveform airborne laser scanning data in urban areas     

Cici Alexander  Kevin Tansey  Jörg Kaduk  David Holland  Nicholas J. Tate 《ISPRS Journal of Photogrammetry and Remote Sensing》2010,65(5):423-432

Airborne laser scanning (ALS) data are increasingly being used for land cover classification. The amplitudes of echoes from targets, available from full-waveform ALS data, have been found to be useful in the classification of land cover. However, the amplitude of an echo is dependent on various factors such as the range and incidence angle, which makes it difficult to develop a classification method which can be applied to full-waveform ALS data from different sites, scanning geometries and sensors. Additional information available from full-waveform ALS data, such as range and echo width, can be used for radiometric calibration, and to derive backscatter cross section. The backscatter cross section of a target is the physical cross sectional area of an idealised isotropic target, which has the same intensity as the selected target. The backscatter coefficient is the backscatter cross section per unit area. In this study, the amplitude, backscatter cross section and backscatter coefficient of echoes from ALS point cloud data collected from two different sites are analysed based on urban land cover classes. The application of decision tree classifiers developed using data from the first study area on the second demonstrates the advantage of using the backscatter coefficient in classification methods, along with spatial attributes. It is shown that the accuracy of classification of the second study area using the backscatter coefficient (kappa coefficient 0.89) is higher than those using the amplitude (kappa coefficient 0.67) or backscatter cross section (kappa coefficient 0.68). This attribute is especially useful for separating road and grass.  相似文献   

青藏高原中东部第四纪冰碛物暴露年龄的测定及其意义   总被引：4，自引：0，他引：4  

赵志中  乔彦松  Joerg SCH 《地学前缘》2006,13(5):316-320

青藏高原上大面积的冰盖通常会对亚洲乃至全球气候产生深远的影响。青藏高原第四纪冰川形成的时间和范围成为人们关注的热点。本研究利用就地成因的宇宙核素暴露年龄测定方法,对唐古拉山和理塘地区的第四纪冰碛物进行了10Be、26Al和21Ne暴露年龄测定,首次获得了青藏高原的第四纪冰川核素暴露年龄。三种核素暴露年龄的一致性显示每期冰碛物沉积有一个确定的暴露时期,测试结果表明唐古拉山和理塘地区出现了两期第四纪冰期,一期形成于距今1·6~8万年,另一期形成于距今16~18万年。  相似文献   

Partial amorphization of experimentally shocked plagioclase: A spectroscopic study     

Lidia Pittarello  Joerg Fritz  Julia Roszjar  Christoph Lenz  Chutimun Chanmuang N.  Christian Koeberl 《Meteoritics & planetary science》2020,55(3):669-678

Shock amorphization of plagioclase, from partial to complete, has been used to evaluate the degree of shock in meteorites. Important information on the shock amplitude can be derived from the measurement of the refractive index in plagioclase, either from mineral separates or in petrographic thin sections. However, this technique is time‐consuming, and associated sample preparations are considered destructive and are not always possible for precious and rare meteorite samples. In addition, plagioclase amorphization is commonly inhomogeneous at the sample scale and a statistically meaningful number of grains must be considered. Here, we apply several nondestructive spectroscopic techniques, such as Raman spectroscopy, photoluminescence, and cathodoluminescence, to plagioclase experimentally shocked at 28 GPa, and thus in the transition regime between crystalline plagioclase and fully amorphous material. Most of the plagioclase was transformed into diaplectic glass at 28 GPa, yet some grains exhibit heterogeneously distributed crystalline domains. This confirms that intrinsic and extrinsic factors lead to local variations in the intensity of the shock pressure within individual plagioclase crystals of homogeneous composition. The amorphization of plagioclase can qualitatively (and potentially also quantitatively) be investigated by spectroscopic techniques, highlighting such local variations in the shock efficiency.  相似文献   

The three-body problem near triple collision     

Joerg Waldvogel 《Celestial Mechanics and Dynamical Astronomy》1976,14(3):287-300

The behaviour of three gravitationally interacting particles in a plane, which approach each other almost on a central configuration, is studied. Linearization near a Lagrangean solution and matching methods lead to the following results: (i) After a close triple encounter in the planar problem of three bodies, one particle generally escapes with an arbitrarily large asymptotic velocity. (ii) Particular cases of actual triple collisions may be extended by the method of Easton.  相似文献   

Evaluating Volumetric Glacier Change Methods Using Airborne Laser Scanning Data     

Philip Claudio Joerg  Michael Zemp 《Geografiska Annaler: Series A, Physical Geography》2014,96(2):135-145

Assessments of geodetic volume change are widely used in glaciology and have a long tradition dating back to the nineteenth century. Over time, the geodetic method and corresponding data storage have been developed further, but the resulting methodological heterogeneity can lead to errors that are difficult to separate from other survey uncertainties. In this study we used high‐resolution airborne laser scanning data from the Findelengletscher in the Swiss Alps to evaluate state‐of‐the‐art volumetric glacier change methods. For the first time we have been able to simulate errors arising from different geodetic methods and spatial resolutions. The evaluation showed that, although the digital elevation models were perfectly co‐registered, systematic and random method‐ and scale‐dependent errors still occurred. These errors have an impact on the resulting volume changes at lower spatial resolutions and may lead to exponentially larger uncertainties. Volume changes from contour methods provided reasonably accurate results, while volumetric change assessments from central profile lines were especially prone to biases at any scale.  相似文献   

A new regularization of the planar problem of three bodies     

Joerg Waldvogel 《Celestial Mechanics and Dynamical Astronomy》1972,6(2):221-231

A new method of simultaneously regularizing the three types of binary collisions in the planar problem of three bodies is developed: The coordinates are transformed by means of certain fourth degree polynomials, and a new independent variable is introduced, too. The proposed transformation is in each binary collision locally equivalent to Levi-Civita's transformation, whereas the singularity corresponding to a triple collision is mapped into infinity. The transformed Hamiltonian is a polynomial of degree 12 in the regularized variables.Presented before the Division of Dynamical Astronomy at the 133rd meeting of the American Astronomical Society, Tampa, Florida, December 6–9, 1970.Department of Aerospace Engineering and Engineering Mechanics.  相似文献   

Mapping from space — cartographic applications of satellite image data     

Joerg Albertz  Ruediger Tauch 《GeoJournal》1994,32(1):29-37

Digital as well as photographic satellite image data offer a high potential of topographic and thematic information. The paper discusses the application of such data for mapping purposes. For the compilation of conventionalTopographic Maps the requirements concerning the geometrical accuracy can easily be met for 1 : 50,000 or even 1 : 25,000. However, the interpretability of the features that are relevant for topography is often the critical factor. Only the Russian KWR-1000 data are suitable for mapping topographic features in 1 : 25,000. Main emphasis is laid on a new map type, theSatellite Image Map. The authors describe the satellite image mapping procedures developed at the Technical University of Berlin and applied in practice by FPK Consulting Engineers. Some related problems are discussed in details, eg mosaicking, merging of different types of data, and integration of graphical elements. An increase in cartographic applications of satellite remote sensing data is anticipated.  相似文献   

Effect of trench-outer rise bending-related faulting on seismic Poisson's ratio and mantle anisotropy: a case study offshore of Southern Central Chile     

Eduardo Contreras-Reyes  Ingo Grevemeyer  Ernst R. Flueh  Martin Scherwath  Joerg Bialas 《Geophysical Journal International》2008,173(1):142-156

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Regional beryllium-10 production rate calibration for late-glacial northeastern North America     

Greg Balco  Jason Briner  Robert C. Finkel  John A. Rayburn  John C. Ridge  Joerg M. Schaefer 《Quaternary Geochronology》2009,4(2):93-107

The major uncertainty in relating cosmogenic-nuclide exposure ages to ages measured by other dating methods comes from extrapolating nuclide production rates measured at globally scattered calibration sites to the sites of unknown age that are to be dated. This uncertainty can be reduced by locating production rate calibration sites that are similar in location and age to the sites to be dated. We use this strategy to reconcile exposure age and radiocarbon deglaciation chronologies for northeastern North America by compiling ¹⁰Be production rate calibration measurements from independently dated late-glacial and early Holocene ice-marginal landforms in this region. ¹⁰Be production rates measured at these sites are 6–12% lower than predicted by the commonly accepted global ¹⁰Be calibration data set used with any published production rate scaling scheme. In addition, the regional calibration data set shows significantly less internal scatter than the global calibration data set. Thus, this calibration data set can be used to improve both the precision and accuracy of exposure dating of regional late-glacial events. For example, if the global calibration data set is used to calculate exposure ages, the exposure-age deglaciation chronology for central New England is inconsistent with the deglaciation chronology inferred from radiocarbon dating and varve stratigraphy. We show that using the regional data set instead makes the exposure age and radiocarbon chronologies consistent. This increases confidence in correlating exposure ages of ice-marginal landforms in northeastern North America with glacial and climate events dated by other means.  相似文献   

A reevaluation of in situ cosmogenic 3He production rates     

Brent M. Goehring  Mark D. Kurz  Greg Balco  Joerg M. Schaefer  Joseph Licciardi  Nathaniel Lifton 《Quaternary Geochronology》2010,5(4):410-418

³He is among the most commonly measured terrestrial cosmogenic nuclides, but an incomplete understanding of the ³He production rate has limited robust interpretation of cosmogenic ³He concentrations. We use new measurements of cosmogenic ³He in olivine from a well-dated lava flow at Tabernacle Hill, Utah, USA, to calibrate the local ³He production rate. The new ³He measurements (n = 8) show excellent internal consistency and yield a sea level high latitude (SLHL) production rate of 123 ± 4 at g^?1 yr^?1 following the Lal (1991)/Stone (2000) scaling model [Lal, D., 1991. Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and erosion models. Earth and Planetary Science Letters, 104, 424–439.; Stone, J.O., 2000. Air pressure and cosmogenic isotope production. Journal of Geophysical Research, 105, 23753–23759.]. We incorporate the new measurements from Tabernacle Hill in a compilation of all published production rate determinations, characterizing the mean global SLHL production rates (e.g. 120 ± 9.4 at g^?1 yr^?1 with Lal (1991)/Stone (2000)). The internal consistency of the global ³He production rate dataset is as good as the other commonly used cosmogenic nuclides. Additionally, ³He production rates in olivine and pyroxene agree within experimental error. The ³He production rates are implemented in an age and erosion rate calculator, forming a new module of the CRONUS-Earth web-based calculator, a simple platform for cosmogenic nuclide data interpretation [Balco, G., Stone, J., Lifton, N.A., and Dunai, T.J., 2008. A complete and easily accessible means of calculating surface exposure ages or erosion rates from ¹⁰Be and ²⁶Al measurements. Quaternary Geochronology, 3, 174–195.]. The ³He calculator is available online at http://www.cronuscalculators.nmt.edu/.  相似文献