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61.
Vishal Chandr Jaunky 《Natural Resources Research》2012,21(2):265-278
The article attempts to test the aluminum consumption–economic growth nexus for 20 rich economies for the period 1970–2009.
Various panel data unit root and cointegration tests are applied. The series are found to be integrated of order one and cointegrated,
especially after controlling for cross-sectional dependence. Moreover, the Blundell–Bond system generalized methods-of-moments
is employed to conduct a panel causality test in a vector error-correction mechanism setting. Unidirectional causality running
from aluminum consumption to real GDP is uncovered in the short-run, while real GDP is found to Granger-cause aluminum consumption
in the long-run. Moreover, a 1% increase in real GDP generates an increase of 0.44% in aluminum consumption in the long-run
for the whole panel. 相似文献
62.
Developing approaches to automate the analysis of the massive amounts of data sent back from the Moon will generate significant benefits for the field of lunar geomorphology. In this paper, we outline an automated method for mapping lunar landforms that is based on digital terrain analysis. An iterative self-organizing (ISO) cluster unsupervised classification enables the automatic mapping of landforms via a series of input raster bands that utilize six geomorphometric parameters. These parameters divide landforms into a number of spatially extended, topographically homogeneous segments that exhibit similar terrain attributes and neighborhood properties. To illustrate the applicability of our approach, we apply it to three representative test sites on the Moon, automatically presenting our results as a thematic landform map. We also quantitatively evaluated this approach using a series of confusion matrices, achieving overall accuracies as high as 83.34% and Kappa coefficients (K) as high as 0.77. An immediate version of our algorithm can also be applied for automatically mapping large-scale lunar landforms and for the quantitative comparison of lunar surface morphologies. 相似文献
63.
A GIS-implemented, deterministic approach for the automated spatial evaluation of geometrical and kinematical properties of
rock slope terrains is presented. Based on spatially distributed directional information on planar geological fabrics and
DEM-derived topographic attribute data, the internal geometry of rock slopes can be characterized on a grid cell basis. For
such computations, different approaches for the analysis and regionalization of available structural directional information
applicable in specific tectonic settings are demonstrated and implemented in a GIS environment. Simple kinematical testing
procedures based on feasibility criteria can be conducted on a pixel basis to determine which failure mechanisms are likely
to occur at particular terrain locations. In combination with hydraulic and strength data on geological discontinuities, scenario-based
rock slope stability evaluations can be performed. For conceptual investigations on rock slope failure processes, a GIS-based
specification tool for a 2-D distinct element code (UDEC) was designed to operate with the GIS-encoded spatially distributed
rock slope data. The concepts of the proposed methodology for rock slope hazard assessments are demonstrated at three different
test sites in Germany. 相似文献
64.
A large street network is likely to contain duplicated or similar sounding street names. These conflicts can cause confusion in communication between people or in machine‐human interaction. Municipal authorities have begun to see the importance of uncovering these existing street name conflicts and mitigating future ones, for improved record keeping, emergency response, etc. However the commonly used Soundex phonetic algorithm is generally considered to produce poor similarity results in terms of uncovering street name conflicts. This study reports on a new fusion algorithm that combines phonetic methods and approximate string matching for street names, weighted by street type suffix (Avenue, Boulevard, Court, etc.), to quantitatively measure the collision/confusion potential presented by a pair of streets. This algorithm is then applied to the entire street network in Greater Melbourne, Australia, and the pattern of collisions at various spatial scales, and within municipalities, is mapped. The goal of this work is to produce better tools that can aid policy makers, administrators and industries dealing with location‐based services to make better decisions when assigning and disambiguating street names. 相似文献
65.
It is well known that high-leverage observations significantly affect the estimation of parameters. In geodetic literature,
mainly redundancy numbers are used for the detection of single high-leverage observations or of single redundant observations. In this paper a further objective method for the detection of groups of important and less important (and thus redundant) observations is developed. In addition, the parameters which are predominantly
affected by these groups of observations are identified. This method thus complements other diagnostics tools, such as, e.g.,
multiple row diagnostics methods as described in statistical literature (see, e.g., Belsley et al. in Regression diagnostics:
identifying influential data and sources of collinearity. Wiley, New York, 1980). The method proposed in this paper is based
on geometric aspects of adjustment theory and uses the singular value decomposition of the design matrix of an adjustment
problem together with cluster analysis methods for regression diagnostics. It can be applied to any geodetic adjustment problem
and can be used for the detection of (groups of) observations that significantly affect the estimated parameters or that are
of negligible impact. One of the advantages of the proposed method is the improvement of the reliability of observation plans
and thus the reduction of the impact of individual observations (and outliers) on the estimated parameters. This is of particular importance for the very long baseline interferometry
technique which serves as an application example of the regression diagnostics tool. 相似文献
66.
In an elementary approach every geometrical height difference between the staff points of a levelling line should have a corresponding
average g value for the determination of potential difference in the Earth’s gravity field. In practice this condition requires as
many gravity data as the number of staff points if linear variation of g is assumed between them. Because of the expensive fieldwork, the necessary data should be supplied from different sources.
This study proposes an alternative solution, which is proved at a test bed located in the Mecsek Mountains, Southwest Hungary,
where a detailed gravity survey, as dense as the staff point density (~1 point/34 m), is available along a 4.3-km-long levelling
line. In the first part of the paper the effect of point density of gravity data on the accuracy of potential difference is
investigated. The average g value is simply derived from two neighbouring g measurements along the levelling line, which are incrementally decimated in the consecutive turns of processing. The results
show that the error of the potential difference between the endpoints of the line exceeds 0.1 mm in terms of length unit if
the sampling distance is greater than 2 km. Thereafter, a suitable method for the densification of the decimated g measurements is provided. It is based on forward gravity modelling utilising a high-resolution digital terrain model, the
normal gravity and the complete Bouguer anomalies. The test shows that the error is only in the order of 10−3mm even if the sampling distance of g measurements is 4 km. As a component of the error sources of levelling, the ambiguity of the levelled height difference which
is the Euclidean distance between the inclined equipotential surfaces is also investigated. Although its effect accumulated
along the test line is almost zero, it reaches 0.15 mm in a 1-km-long intermediate section of the line. 相似文献
67.
Johannes Bouman Sietse Rispens Thomas Gruber Radboud Koop Ernst Schrama Pieter Visser Carl Christian Tscherning Martin Veicherts 《Journal of Geodesy》2009,83(7):659-678
One of the products derived from the gravity field and steady-state ocean circulation explorer (GOCE) observations are the
gravity gradients. These gravity gradients are provided in the gradiometer reference frame (GRF) and are calibrated in-flight
using satellite shaking and star sensor data. To use these gravity gradients for application in Earth scienes and gravity
field analysis, additional preprocessing needs to be done, including corrections for temporal gravity field signals to isolate
the static gravity field part, screening for outliers, calibration by comparison with existing external gravity field information
and error assessment. The temporal gravity gradient corrections consist of tidal and nontidal corrections. These are all generally
below the gravity gradient error level, which is predicted to show a 1/f behaviour for low frequencies. In the outlier detection, the 1/f error is compensated for by subtracting a local median from the data, while the data error is assessed using the median absolute
deviation. The local median acts as a high-pass filter and it is robust as is the median absolute deviation. Three different
methods have been implemented for the calibration of the gravity gradients. All three methods use a high-pass filter to compensate
for the 1/f gravity gradient error. The baseline method uses state-of-the-art global gravity field models and the most accurate results
are obtained if star sensor misalignments are estimated along with the calibration parameters. A second calibration method
uses GOCE GPS data to estimate a low-degree gravity field model as well as gravity gradient scale factors. Both methods allow
to estimate gravity gradient scale factors down to the 10−3 level. The third calibration method uses high accurate terrestrial gravity data in selected regions to validate the gravity
gradient scale factors, focussing on the measurement band. Gravity gradient scale factors may be estimated down to the 10−2 level with this method. 相似文献
68.
Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination 总被引:7,自引:5,他引:7
Adrian Jäggi R. Dach O. Montenbruck U. Hugentobler H. Bock G. Beutler 《Journal of Geodesy》2009,83(12):1145-1162
Most satellites in a low-Earth orbit (LEO) with demanding requirements on precise orbit determination (POD) are equipped with
on-board receivers to collect the observations from Global Navigation Satellite systems (GNSS), such as the Global Positioning
System (GPS). Limiting factors for LEO POD are nowadays mainly encountered with the modeling of the carrier phase observations,
where a precise knowledge of the phase center location of the GNSS antennas is a prerequisite for high-precision orbit analyses.
Since 5 November 2006 (GPS week 1400), absolute instead of relative values for the phase center location of GNSS receiver
and transmitter antennas are adopted in the processing standards of the International GNSS Service (IGS). The absolute phase
center modeling is based on robot calibrations for a number of terrestrial receiver antennas, whereas compatible antenna models
were subsequently derived for the remaining terrestrial receiver antennas by conversion (from relative corrections), and for
the GNSS transmitter antennas by estimation. However, consistent receiver antenna models for space missions such as GRACE
and TerraSAR-X, which are equipped with non-geodetic receiver antennas, are only available since a short time from robot calibrations.
We use GPS data of the aforementioned LEOs of the year 2007 together with the absolute antenna modeling to assess the presently
achieved accuracy from state-of-the-art reduced-dynamic LEO POD strategies for absolute and relative navigation. Near-field
multipath and cross-talk with active GPS occultation antennas turn out to be important and significant sources for systematic
carrier phase measurement errors that are encountered in the actual spacecraft environments. We assess different methodologies
for the in-flight determination of empirical phase pattern corrections for LEO receiver antennas and discuss their impact
on POD. By means of independent K-band measurements, we show that zero-difference GRACE orbits can be significantly improved
from about 10 to 6 mm K-band standard deviation when taking empirical phase corrections into account, and assess the impact
of the corrections on precise baseline estimates and further applications such as gravity field recovery from kinematic LEO
positions. 相似文献
69.
Georges Balmino 《Journal of Geodesy》2009,83(10):989-995
We have applied efficient methods for computing variances and covariances of functions of a global gravity field model expanded
in spherical harmonics, using the full variance–covariance matrix of the coefficients. Examples are given with recent models
derived from GRACE (up to degree and order 150), and with simulated GOCE derived solutions (up to degree and order 200). 相似文献
70.
Lars E. Sjöberg 《Journal of Geodesy》2009,83(10):967-972
The topographic bias is defined as the error/bias committed by continuing the external gravity field inside the topographic
masses by a harmonic function. We study the topographic bias given by a digital terrain model defined by a spherical template,
and we show that the topographic bias is given only by the potential of an inner-zone cap, and it equals the bias of the Bouguer
shell, independent of the size of the cap. Then we study the effect on the real Earth by decomposing its topography into a
template, and we show also in this case that the topographic bias is that of the Bouguer shell, independent of the shape of
the terrain. Finally, we show that the topographic potential of the terrain at the geoid can be determined to any precision
by a Taylor expansion outside the Earth’s surface. The last statement is demonstrated by a Taylor expansion to fourth order. 相似文献