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1.
Gianfranco Piras Kieran P. Donaghy Giuseppe Arbia 《Journal of Geographical Systems》2007,9(4):311-344
This paper presents an innovative approach to the study of regional economic dynamics within a nonlinear continuous-time econometric
framework—a generalized specification of the Lotka–Volterra system of equations. This specification, which accounts for interdependent
behavior of three industrial sectors and spillover effects of activities in neighboring regions, is employed in an analysis
of five Italian regions between 1980 and 2003. For these regions, we report estimation results, characterize the varying systems
dynamics, analyze the models’ local and global stability properties, and determine via sensitivity analyses which structural
features appear to exert the greatest influence on these properties.
相似文献
Kieran P. DonaghyEmail: |
2.
The location of new homes defines the urban–rural fringe and determines many facets of the urban–rural interaction set in
motion by construction of new homes in previously rural areas. Home, neighborhood and school district characteristics play
a crucial role in determining the spatial location of new residential construction, which in turn defines the boundary and
spatial extent of the urban–rural fringe. We develop and apply a spatial hedonic variant of the Blinder (J Hum Resour 8:436–455,
1973) and Oaxaca (Int Econ Rev 9:693–709, 1973) price decomposition to newer versus older home sales in the Columbus, Ohio metropolitan area during the year 2000. The preferences
of buyers of newer homes are compared to those who purchased the nearest neighboring older home located in the same census
block group, during the same year. Use of the nearest older home purchased in the same location represents a methodology to
control for various neighborhood, social–economic-demographic and school district characteristics that influence home prices.
Since newer homes reflect current preferences for home characteristics while older homes reflect past preferences for these
characteristics, we use the price differentials between newer and older home sales in the Blinder–Oaxaca decomposition to
assess the relative significance of various house characteristics to home buyers.
相似文献
Joni S. CharlesEmail: |
3.
Since the assumption of all stations tracking the same satellites with identical weights was previously employed by Shen and
Xu (GPS Solut 12:99–108, 2008) to derive the simplified GNSS single- and double-differenced equivalent equations, this supplementary paper expands these
simplified equations in the case of each station tracking different satellites with elevation-dependent weights. Numerical
experiments are performed to demonstrate the computational efficiency of the simplified equivalent algorithm relative to the
traditional method in various scenarios of multi-baseline solutions with tracking different satellites. The fast computational
speed of the simplified equivalent algorithm will potentially benefit the local, regional and even global GNSS multi-baseline
solutions as well as the combined GNSS application.
相似文献
Guochang XuEmail: |
4.
Hierarchical spatial interaction among the Italian regions: a nonlinear relative dynamics approach 总被引:2,自引:2,他引:0
Regional interactions and spillover effects should be considered as important factors in growth analysis of regional economies.
Using modified versions of the Dendrinos–Sonis model, this paper analyses the spatial hierarchical system of Italy. The interaction
among Italian regions is considered at three different levels of spatial aggregation, the NUTS-1, NUTS-2 and NUTS-3 levels.
Compared to more popular spatial econometric approaches, the Dendrinos–Sonis model and its extensions provide greater flexibility
in the way interaction between regions is handled but the results strongly depend on the choice of a reference region.
相似文献
Geoffrey J. D. HewingsEmail: |
5.
Separate space- or time-lags have been considered regularly in data analyses; as space–time models are more recently being
studied extensively in data analytic fashion, joint estimation of both lags has to be considered explicitly. This paper addresses
this issue, taking into special consideration parametric parsimony together with specification richness; use of the bivariate
Poisson frequency distribution is advocated and applied to an empirical case. The relation of this approach to random effects
specifications is investigated. Data for Belgian regional products constitute the empirical case study.
相似文献
Daniel A. GriffithEmail: |
6.
Small-scale irregularities in the background electron density of the ionosphere can cause rapid fluctuations in the amplitude
and phase of radio signals passing through it. These rapid fluctuations are known as scintillation and can cause a Global
Positioning System (GPS) receiver to lose lock on a signal. This could compromise the integrity of a safety of life system
based on GPS, operating in auroral regions. In this paper, the relationship between the loss of lock on GPS signals and ionospheric
scintillation in auroral regions is explored. The period from 8 to 14 November 2004 is selected for this study, as it includes
both geomagnetically quiet and disturbed conditions. Phase and amplitude scintillation are measured by GPS receivers located
at three sites in Northern Scandinavia, and correlated with losses of signal lock in receivers at varying distances from the
scintillation receivers. Local multi-path effects are screened out by rejection of low-elevation data from the analysis. The
results indicate that losses of lock are more closely related to rapid fluctuations in the phase rather than the amplitude
of the received signal. This supports the idea, suggested by Humphreys et al. (2005) (performance of GPS carrier tracking loops during ionospheric scintillations. Proceedings Internationsl Ionospheric Effects
Symposium 3–5 May 2005), that a wide loop bandwidth may be preferred for receivers operating at auroral latitudes. Evidence from the Imaging Riometer
for Ionospheric Studies (IRIS) appears to suggest that, for this particular storm, precipitation of particles in the D/E regions
may be the mechanism that drives the rapid phase fluctuations in the signal.
相似文献
Robert W. MeggsEmail: |
7.
A spatiotemporal analysis of aggregate labour force behaviour by sex and age across the European Union 总被引:2,自引:1,他引:1
J. Paul Elhorst 《Journal of Geographical Systems》2008,10(2):167-190
This study investigates the causes of variation in age-specific male and female labour force participation rates using annual
data from 154 regions across ten European Union member states for the period 1983–1997. Regional participation rates appear
to be strongly correlated in time, weakly correlated in space and to parallel their national counterparts. An econometric
model is designed consistent with these empirical findings. To control for potential endogeneity of the explanatory variables,
we use an instrumental variables estimation scheme based on a matrix exponential spatial specification of the error terms.
Many empirical studies of aggregate labour force behaviour have ignored population distribution effects, relying instead on
the representative-agent paradigm. In order for representative-agent models to accurately describe aggregate behaviour, all
marginal reactions of individuals to changes in aggregate variables must be identical. It turns out that this condition cannot
apply to individuals across different sex/age groups.
相似文献
J. Paul ElhorstEmail: |
8.
Alan T. Murray Timothy C. Matisziw Tony H. Grubesic 《Journal of Geographical Systems》2007,9(2):103-117
Effective management of critical network infrastructure requires the assessment of potential interdiction scenarios. Optimization
approaches have been essential for identifying and evaluating such scenarios in networked systems. Although a primary function
of any network is the distribution of flow between origins and destinations, the complexity and difficulty of mathematically
abstracting interdiction impacts on connectivity or flow has been a challenge for researchers. This paper presents an optimization
approach for identifying interdiction bounds with respect to connectivity and/or flow associated with a system of origins
and destinations. Application results for telecommunications flow are presented, illustrating the capabilities of this approach.
相似文献
Alan T. Murray (Corresponding author)Email: |
Timothy C. MatisziwEmail: |
Tony H. GrubesicEmail: |
9.
An exploratory analysis of hierarchical spatial interaction: the case of regional income shares in Indonesia 总被引:3,自引:3,他引:0
Suahasil Nazara Geoffrey J. D. Hewings Michael Sonis 《Journal of Geographical Systems》2006,8(3):253-268
Regional interaction is generally understood as implying movement between regions at the same level of an hierarchy. This paper extends the notion to include an hierarchical system, thus facilitating the consideration of vertical interaction in the analysis of regional interaction. Obviously, vertical interaction is not altogether a new concept. One could find this concept in many analyses related to national-local or federal-state relationships. This paper treats hierarchy in a strict sense; spatial units are interacting one with another within, but not between, presumed super regions. A particular example drawn in this paper is the province-region relationships for the case of Indonesia. In this framework, provinces form a region, and regions form the nation. The Dendrinos–Sonis model is then used as the basis for measuring the hierarchical spatial interaction in Indonesia. The analysis will explore the degree to which complementarity and competitive interaction revealed at one level in the hierarchy persist at lower or higher levels.
相似文献
Geoffrey J. D. HewingsEmail: |
10.
Digital mobile mapping, the method that integrates digital imaging with direct geo-referencing, has developed rapidly over
the past 15 years. The Kalman filter (KF) is considered an optimal estimation tool for real-time INS/GPS integrated kinematic
positioning and orientation determination. However, the accuracy requirements of general mobile mapping applications cannot
be easily achieved even when using the KF scheme. Therefore, this study proposes an intelligent scheme combining ANN and RTS
backward smoother to overcome the limitations of KF and to enhance the overall accuracy of attitude determination for tactical
grade and MEMS INS/GPS integrated systems.
相似文献
Yun-Wen Huang (Corresponding author)Email: |
11.
Computer algebra solution of the GPS N-points problem 总被引:1,自引:0,他引:1
A computer algebra solution is applied here to develop and evaluate algorithms for solving the basic GPS navigation problem: finding a point position using four or more pseudoranges at one
epoch (the GPS N-points problem). Using Mathematica 5.2 software, the GPS N-points problem is solved numerically, symbolically, semi-symbolically, and with Gauss–Jacobi, on a work station. For the case of N > 4, two minimization approaches based on residuals and distance norms are evaluated for the direct numerical solution and their computational duration is compared. For N = 4, it is demonstrated that the symbolic computation is twice as fast as the iterative direct numerical method. For N = 6, the direct numerical solution is twice as fast as the semi-symbolic, with the residual minimization requiring less computation
time compared to the minimization of the distance norm. Gauss–Jacobi requires eight times more computation time than the direct
numerical solution. It does, however, have the advantage of diagnosing poor satellite geometry and outliers. Besides offering
a complete evaluation of these algorithms, we have developed Mathematica 5.2 code (a notebook file) for these algorithms (i.e., Sturmfel’s resultant, Dixon’s resultants, Groebner basis, reduced
Groebner basis and Gauss–Jacobi). These are accessible to any geodesist, geophysicist, or geoinformation scientist via the
GPS Toolbox () website or the Wolfram Information Center ().
相似文献
Erik W. GrafarendEmail: |
12.
A constrained LAMBDA method for GPS attitude determination 总被引:4,自引:0,他引:4
An improved method to obtain fixed integer ambiguity in GPS attitude determination is presented. Known conditions are utilized
as constraints to acquire attitude information when the float solution and its variance–covariance matrix are not accurate
enough. The searching ellipsoidal region is first expanded to compensate for errors caused by the inaccurate float solution.
Then the constraints are used to shrink the region to a proper size, which maintains the true integer ambiguity. Experimental
results demonstrate that this scheme gives a fast search time and a higher success rate in determining the fixed integer ambiguity
than the unconstrained method. The accuracy of attitude angles is also improved.
相似文献
Bo WangEmail: |
13.
Modeling network autocorrelation within migration flows by eigenvector spatial filtering 总被引:8,自引:5,他引:3
Yongwan Chun 《Journal of Geographical Systems》2008,10(4):317-344
Although the assumption of independence among interaction flows frequently is engaged in spatial interaction modeling, in
many circumstances it leads to misspecified models and incorrect inferences. An informed approach is to explicitly incorporate
an assumed relationship structure among the interaction flows, and to explicitly model the network autocorrelation. This paper
illustrates such an approach in the context of U.S. interstate migration flows. Behavioral assumptions, similar to those of
the intervening opportunities or the competing destinations concepts, exemplify how to specify network flows that are related
to particular origin–destination combinations. The stepwise incorporation of eigenvectors, which are extracted from a network
link matrix, captures the network autocorrelation in a Poisson regression model specification context. Spatial autocorrelation
in Poisson regression is measured by the test statistic of Jacqmin-Gadda et al. (Stat Med
16(11):1283–1297, 1997). Results show that estimated regression parameters in the spatial filtering interaction model become
more intuitively interpretable.
相似文献
Yongwan ChunEmail: |
14.
The accuracy of standalone GPS positioning improved significantly when Selective Availability was turned off in May 2000. With the availability of various public GPS related products including precise satellite orbits and clocks, and ionosphere maps, a single-frequency standalone user can experience even a further improvement of the position accuracy. Next, using carrier phase measurements becomes crucial to smoothen the pseudorange noise. In this contribution, the most critical sources of error in single-frequency standalone positioning will be reviewed and different approaches to mitigate the errors will be considered. An optimal filter (using also carrier phase measurements) will be deployed. The final approach will then be evaluated in a decently long static test with receivers located in different regions of the world. Kinematic experiments have also been performed in various scenarios including a highly dynamic flight trial. The accuracy, in general, can be confirmed at 0.5 m horizontal and 1 m vertical, with static tests. Ultimate results demonstrate an accuracy close to 2 dm (95%) for the horizontal position components and 5 dm (95%) for the vertical in the flight experiment.
相似文献
Anh Quan LeEmail: |
15.
In this article, an algorithm for clock offset estimation of the GPS satellites is presented. The algorithm is based on a
Kalman-filter and processes undifferenced code and carrier-phase measurements of a global tracking network. The clock offset
and drift of the satellite clocks are estimated along with tracking station clock offsets, tropospheric zenith path delay
and carrier-phase ambiguities. The article provides a brief overview of already existing near-real-time and real-time clock
products. The filter algorithm and data processing scheme is presented. Finally, the accuracy of the orbit and clock product
is assessed with a precise orbit determination of the MetOp satellite and compared to results gained with other real-time
products.
相似文献
André HauschildEmail: |
16.
Oliver Montenbruck Yago Andres Heike Bock Tom van Helleputte Jose van den Ijssel Marc Loiselet Christian Marquardt Pierluigi Silvestrin Pieter Visser Yoke Yoon 《GPS Solutions》2008,12(4):289-299
The global navigation satellite system receiver for atmospheric sounding (GRAS) on MetOp-A is the first European GPS receiver
providing dual-frequency navigation and occultation measurements from a spaceborne platform on a routine basis. The receiver
is based on ESA’s AGGA-2 correlator chip, which implements a high-quality tracking scheme for semi-codeless P(Y) code tracking
on the L1 and L2 frequency. Data collected with the zenith antenna on MetOp-A have been used to perform an in-flight characterization
of the GRAS instrument with focus on the tracking and navigation performance. Besides an assessment of the receiver noise
and systematic measurement errors, the study addresses the precise orbit determination accuracy achievable with the GRAS receiver.
A consistency on the 5 cm level is demonstrated for reduced dynamics orbit solutions computed independently by four different
agencies and software packages. With purely kinematic solutions, 10 cm accuracy is obtained. As a part of the analysis, an
empirical antenna offset correction and preliminary phase center correction map are derived, which notably reduce the carrier
phase residuals and improve the consistency of kinematic orbit determination results.
相似文献
Oliver MontenbruckEmail: |
17.
In this paper a MATLAB toolbox for determining the attitude of a rigid platform by means of multiple non-dedicated antennas
using global positioning system is presented. The programs embedded in this toolbox cover the RINEX data analysis, single
point positioning, differential positioning, coordinate conversion, attitude determination, and other auxiliary functions.
After forming the baselines through double-differenced (carrier phase smoothed) code observables, the attitude parameters
are obtained by applying the direct attitude computation and the least squares attitude estimation. The theoretical background
is summarized, and some hints regarding the software implementation are given in the paper. Moreover, improvements yielding
an expanded functionality are proposed.
相似文献
Zhen DaiEmail: |
18.
While there is a large literature on the form of epidemic waves in the time domain, models of their structure and shape in the spatial domain remain poorly developed. This paper concentrates on the changing spatial distribution of an epidemic wave over time and presents a simple method for identifying the leading and trailing edges of the spatial advance and retreat of such waves. Analysis of edge characteristics is used to (a) disaggregate waves into ‘swash’ and ‘backwash’ stages, (b) measure the phase transitions of areas from susceptible, S, through infective, I, to recovered, R, status (S → I → R) as dimensionless integrals and (c) estimate a spatial version of the basic reproduction number, R
0. The methods used are illustrated by application to measles waves in Iceland over a 60-year period from 1915 to 1974. Extensions of the methods for use with more complex waves are possible through modifying the threshold values used to define the start and end points of an event.
相似文献
Peter HaggettEmail: |
19.
Modeling spatial autocorrelation in spatial interaction data: empirical evidence from 2002 Germany journey-to-work flows 总被引:3,自引:3,他引:0
Daniel A. Griffith 《Journal of Geographical Systems》2009,11(2):117-140
Since before the inception of work by Okabe, the intermingling of spatial autocorrelation (i.e., local distance and configuration)
and distance decay (i.e., global distance) effects has been suspected in spatial interaction data. This convolution was first
treated conceptually because technology and methodology did not exist at the time to easily or fully address spatial autocorrelation
effects within spatial interaction model specifications. Today, however, sufficient computer power coupled with eigenfunction-based
spatial filtering offers a means for accommodating spatial autocorrelation effects within a spatial interaction model for
modest-sized problems. In keeping with Okabe’s more recent efforts to dissemination spatial analysis tools, this paper summarizes
how to implement the methodology utilized to analyze a particular empirical flows dataset.
相似文献
Daniel A. GriffithEmail: |
20.
The architecture of the ultra-tight GPS/INS/PL integration is the key to its successful performance; the main feature of this
architecture is the Doppler feedback to the GPS receiver tracking loops. This Doppler derived from INS, when integrated with
the carrier tracking loops, removes the Doppler due to vehicle dynamics from the GPS/PL signal thereby achieving a significant
reduction in the carrier tracking loop bandwidth. The bandwidth reduction provides several advantages such as: improvement
in anti-jamming performance, and increase in post correlated signal strength which in turn increases the dynamic range and
accuracy of measurements. Therefore, any degradation in the derived Doppler estimates will directly affect the tracking loop
bandwidth and hence its performance. The quadrature signals from the receiver correlator, I (in-phase) and Q (quadrature),
form the measurements, whereas the inertial sensor errors, position, velocity and attitude errors form the states of the complementary
Kalman filter. To specify a reliable measurement model of the filter for this type of integrated system, a good understanding
of GPS/PL signal characteristics is essential. It is shown in this paper that phase and frequency errors are the variables
that relate the measurements and the states in the Kalman filter. The main focus of this paper is to establish the fundamental
mathematical relationships that form the measurement model, and to show explicitly how the system error states are related
to the GPS/PL signals. The derived mathematical relationships encapsulated in a Kalman filter, are tested by simulation and
shown to be valid.
相似文献
Ravindra Babu (Corresponding author)Email: |
Jinling WangEmail: |