共查询到20条相似文献,搜索用时 578 毫秒
1.
M. C. Santos P. Vaníček W. E. Featherstone R. Kingdon A. Ellmann B. -A. Martin M. Kuhn R. Tenzer 《Journal of Geodesy》2006,80(12):691-704
Following our earlier definition of the rigorous orthometric height [J Geod 79(1-3):82–92 (2005)] we present the derivation and calculation of the differences between this and the Helmert orthometric height, which is embedded in the vertical datums used in numerous countries. By way of comparison, we also consider Mader and Niethammer’s refinements to the Helmert orthometric height. For a profile across the Canadian Rocky Mountains (maximum height of ~2,800 m), the rigorous correction to Helmert’s height reaches ~13 cm, whereas the Mader and Niethammer corrections only reach ~3 cm. The discrepancy is due mostly to the rigorous correction’s consideration of the geoid-generated gravity disturbance. We also point out that several of the terms derived here are the same as those used in regional gravimetric geoid models, thus simplifying their implementation. This will enable those who currently use Helmert orthometric heights to upgrade them to a more rigorous height system based on the Earth’s gravity field and one that is more compatible with a regional geoid model. 相似文献
2.
LIQi CAOJian 《地球空间信息科学学报》2004,7(2):101-103
This paper is to construct a “digital local, regional, region“ information framework based on the technology of “SIG“ and its significance and application to the regional sustainable development evaluation system. First, the concept of the “grid computing“ and “SIG“ is interpreted and discussed, then the relationship between the “grid computing“ and “digital region“ is analyzed, and the framework of the “digital region“ is put forward. Finally, the significance and application of “grid computing“ to the “region sustainable development evaluation system“ are discussed. 相似文献
3.
We present an alternate mathematical technique than contemporary spherical harmonics to approximate the geopotential based
on triangulated spherical spline functions, which are smooth piecewise spherical harmonic polynomials over spherical triangulations.
The new method is capable of multi-spatial resolution modeling and could thus enhance spatial resolutions for regional gravity
field inversion using data from space gravimetry missions such as CHAMP, GRACE or GOCE. First, we propose to use the minimal
energy spherical spline interpolation to find a good approximation of the geopotential at the orbital altitude of the satellite.
Then we explain how to solve Laplace’s equation on the Earth’s exterior to compute a spherical spline to approximate the geopotential
at the Earth’s surface. We propose a domain decomposition technique, which can compute an approximation of the minimal energy
spherical spline interpolation on the orbital altitude and a multiple star technique to compute the spherical spline approximation
by the collocation method. We prove that the spherical spline constructed by means of the domain decomposition technique converges
to the minimal energy spline interpolation. We also prove that the modeled spline geopotential is continuous from the satellite
altitude down to the Earth’s surface. We have implemented the two computational algorithms and applied them in a numerical
experiment using simulated CHAMP geopotential observations computed at satellite altitude (450 km) assuming EGM96 (n
max = 90) is the truth model. We then validate our approach by comparing the computed geopotential values using the resulting
spherical spline model down to the Earth’s surface, with the truth EGM96 values over several study regions. Our numerical
evidence demonstrates that the algorithms produce a viable alternative of regional gravity field solution potentially exploiting
the full accuracy of data from space gravimetry missions. The major advantage of our method is that it allows us to compute
the geopotential over the regions of interest as well as enhancing the spatial resolution commensurable with the characteristics
of satellite coverage, which could not be done using a global spherical harmonic representation.
The results in this paper are based on the research supported by the National Science Foundation under the grant no. 0327577. 相似文献
4.
The global positioning system (GPS) model is distinctive in the way that the unknown parameters are not only real-valued,
the baseline coordinates, but also integers, the phase ambiguities. The GPS model therefore leads to a mixed integer–real-valued
estimation problem. Common solutions are the float solution, which ignores the ambiguities being integers, or the fixed solution,
where the ambiguities are estimated as integers and then are fixed. Confidence regions, so-called HPD (highest posterior density)
regions, for the GPS baselines are derived by Bayesian statistics. They take care of the integer character of the phase ambiguities
but still consider them as unknown parameters. Estimating these confidence regions leads to a numerical integration problem
which is solved by Monte Carlo methods. This is computationally expensive so that approximations of the confidence regions
are also developed. In an example it is shown that for a high confidence level the confidence region consists of more than
one region.
Received: 1 February 2001 / Accepted: 18 July 2001 相似文献
5.
Deniz Karagulle Charlie Frye Roger Sayre Sean Breyer Peter Aniello Randy Vaughan Dawn Wright 《Transactions in GIS》2017,21(5):1040-1060
In 1964, E.H. Hammond proposed criteria for classifying and mapping physiographic regions of the United States. Hammond produced a map entitled “Classes of Land Surface Form in the Forty‐Eight States, USA”, which is regarded as a pioneering and rigorous treatment of regional physiography. Several researchers automated Hammond?s model in GIS. However, these were local or regional in application, and resulted in inadequate characterization of tablelands. We used a global 250 m DEM to produce a new characterization of global Hammond landform regions. The improved algorithm we developed for the regional landform modeling: (1) incorporated a profile parameter for the delineation of tablelands; (2) accommodated negative elevation data values; (3) allowed neighborhood analysis window (NAW) size to vary between parameters; (4) more accurately bounded plains regions; and (5) mapped landform regions as opposed to discrete landform features. The new global Hammond landform regions product builds on an existing global Hammond landform features product developed by the U.S. Geological Survey, which, while globally comprehensive, did not include tablelands, used a fixed NAW size, and essentially classified pixels rather than regions. Our algorithm also permits the disaggregation of “mixed” Hammond types (e.g. plains with high mountains) into their component parts. 相似文献
6.
In this paper we start from a continuous time framework derived from the classical predator-prey model in order to analyze the recent dynamics of regional evolution in the EU. The model describes a system of interrelated units obeying a complex functional dynamics that at any moment may encompass divergent forces. After briefly reviewing the modeling framework presented elsewhere (Arbia and Paelinck 2002), we consider the dynamics of per-capita income in 119 NUTS-2 European regions in the years 1985–1999, and fit the model using Simultaneous Dynamic Least Squares (Paelinck 1996b). The model is shown to fit the empirical data well. The – potential divergence – leads up to a formidable coordination task for public authorities responsible for regional policies, as they are supposed – if their aim is absolute convergence in an economic sense, meaning equalizing incomes per head – to produce at any time a consistent set of regional policies for all the regions concerned, and not only for the less developed ones. 相似文献
7.
Pammi Nitin Sinha Nilanchal Patel Ayyemperumal T. Jeyaseelan Vivek K. Singh 《Journal of the Indian Society of Remote Sensing》2011,39(2):225-233
Urbanization incepts serious challenges of growth and its management. The issues of urbanization manifest in the form of overcrowding,
congestion, insufficient infrastructure, inadequate service provisioning, environmental degradation, pollution etc and affect
the socioeconomic development of the city. Ranchi, the capital of newly formed state of Jharkhand (India) has been witnessing
the same scenario; raising the question of its planning and management of growth to make it more efficient and sustainable.
It hoists the necessity to study the pattern of urbanization and its impact on other landuse/landcover categories in Ranchi
city. In order to assess the urbanization pattern and spatio-temporal dynamics in the study area, the changing pattern of
the three significant patch parameters viz. patch frequency, largest patch size and average patch size of all affected landuse/landcover
categories over a time gradient representing the pre-capital and post-capital formation phases of the Ranchi city have been
analyzed. The two conventional landscape indices viz. Shannon’s diversity Index and Simpson’s diversity index and a newly
developed index ‘Normalized Patch size Range Index’ have been employed in the analyses which not only ascertained the finding
derived but also provided meaningful insights pertaining to the spatio-temporal urban landscape dynamics prevailing in the
Ranchi city. 相似文献
8.
The problems of the earth’s gravity fields’ visualization are both focus and puzzle currently. Aiming at multiresolution rendering,
modeling of the Earth’s gravity fields’ data is discussed in the paper by using LOD algorithm based on Quad Tree. First, this
paper employed the method of LOD based on Quad Tree to divide up the regional gravity anomaly data, introduced the combined
node evaluation system that was composed of viewpoint related and roughness related systems, and then eliminated the T-cracks
that appeared among the gravity anomaly data grids with different resolutions. The test results demonstrated that the gravity
anomaly data grids’ rendering effects were living, and the computational power was low. Therefore, the proposed algorithm
was a suitable method for modeling the gravity anomaly data and has potential applications in visualization of the earth’s
gravity fields. 相似文献
9.
H. S. Sudhira T. V. Ramachandra Karthik S. Raj K. S. Jagadish 《Journal of the Indian Society of Remote Sensing》2003,31(4):299-311
Urban growth identification, quantification, knowledge of rate and the trends of growth would help in regional planning for
better infrastructure provision in environmentally sound way. This requires analysis of spatial and temporal data, which help
in quantifying the trends of growth on spatial scale. Emerging technologies such as Remote Sensing, Geographic Information
System (GIS) along with Global Positioning System (GPS) help in this regard. Remote sensing aids in the collection of temporal
data and GIS helps in spatial analysis. This paper focuses on the analysis of urban growth pattern in the form of either radial
or linear sprawl along the Bangalore — Mysore highway. Various GIS base layers such as built-up areas along the highway, road
network, village boundary etc. were generated using collateral data such as the Survey of India toposheet, etc. Further, this
analysis was complemented with the computation of Shannon’s entropy, which helped in identifying prevalent sprawl zone, rate
of growth and in delineating potential sprawl locations. The computation Shannon’s entropy helped in delineating regions with
dispersed and compact growth. This study reveals that the Bangalore North and South taluks contributed mainly to the sprawl
with 559% increase in built-up area over a period of 28 years and high degree of dispersion. The Mysore and Srirangapatna
region showed 128% change in built-up area and a high potential for sprawl with slightly high dispersion. The degree of sprawl
was found to be directly proportional to the distances from the cities. 相似文献
10.
Wavelet Modeling of Regional and Temporal Variations of the Earth’s Gravitational Potential Observed by GRACE 总被引:1,自引:0,他引:1
This work is dedicated to the wavelet modeling of regional and temporal variations of the Earth’s gravitational potential
observed by the GRACE (gravity recovery and climate experiment) satellite mission. In the first part, all required mathematical
tools and methods involving spherical wavelets are provided. Then, we apply our method to monthly GRACE gravity fields. A
strong seasonal signal can be identified which is restricted to areas where large-scale redistributions of continental water
mass are expected. This assumption is analyzed and verified by comparing the time-series of regionally obtained wavelet coefficients
of the gravitational signal originating from hydrology models and the gravitational potential observed by GRACE. The results
are in good agreement with previous studies and illustrate that wavelets are an appropriate tool to investigate regional effects
in the Earth’s gravitational field.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
11.
Over the last four decades exploitation of natural resources to meet increasing societal demands for land based products has
caused significant changes in land use and land cover not only in nature’s best gifted regions but also environmentally sensitive
arid regions. Through digital interpretation of IRS LISS-III data of 2004 supported with field survey, the present land use
map of Jhunjhunun district of arid Rajasthan has been prepared. Agriculture is the dominant land use constituting 84% (including
38% irrigated cropland) area. The land use changes over time and space are worked out by comparing with Landsat 2 MSS data
of 1975 and Land use/land cover map of 1988–89. These changes are correlated by analyzing historical land use and cropping
pattern data from 1957–58 to 2004–05. The region witnessed record increase in irrigated area but sharply depleted ground water
and rendered hectares of irrigated double cropland into dry land agriculture. Strategies and technologies are suggested for
sustainable use and management of different category of land. 相似文献
12.
Sandy Dall’erba 《Journal of Geographical Systems》2005,7(2):207-227
This paper estimates the evolution of labor productivity disparities among 48 Spanish regions over 1980–1996 according to the concepts of - and -convergence. The results of -convergence emphasize the importance of including the impact of neighboring locations productivity and a disaggregate analysis at a sectoral level. In order to measure the narrowing of inequalities, we examine -convergence and reveal that convergence occurs in aggregate labor productivity but not in productivities per sector. The reason comes from a transfer of resources from agriculture towards more productive sectors that has been more pronounced in the poor regions than in the rich ones.The author would like to thank Julie Le Gallo, an anonymous referee, and the participants of the 50th North American Meetings of the RSAI and of the 43rd Annual Meeting of the WRSA for their valuable comments. This paper won the first place the 2004 Tiebout Prize competition, which was awarded at the WRSA meeting, Hawaii, USA, February 26–28. 相似文献
13.
The change of land use/cover and characteristics of landscape pattern in arid areas oasis: An application in Jinghe,Xinjiang 总被引:1,自引:0,他引:1
This paper uses 3S technology in macroscopic. Combining the integrated technology of ecological quantity analytical method
with GIS technology through ArcGIS and Fragstats, the authors study the images of 1972, 1990, 2001, and 2005 and obtained
land use data in Jinghe County. Then, the change of land use/cover and landscape pattern had been analyzed in the Jinghe County
of Xinjiang. The conclusions were as follows: (1) The trend of LUCC is that the area of oasis expands slowly in nearly 33
years between 1972 to 2005 in Jinghe County. (2) The water area is mainly influenced by Ebinur Lake, so the area expands a
little in this period. (3) The area of salinization-land expands at first and reduces later. The area of sand land decreases
and the other land class increases, while the probability of transfer is always high. (4) Landscape change is also obvious
throughout the decades. Overall, landscape density increases, the largest path index decreases at first and expends later,
the weight area index decreases, and the shape of landscape becomes regulated. The nearest distances, the degrees of reunite,
and outspread decreases. It shows that the connection of the main path in 1972 is better than 2005, wherein the patch becomes
more complex. From the changes of Shannon’s Diversity Index and Shannon’s Evenness Index, we know that the diversity of landscape
and the Interspersion Juxtaposition Index increase. The degree of diversity landscape and fragmentation increase also shows
that the land uses become more complex. All in all, it is essential to intensify the spatial relationships among landscape
elements and to maintain the continuity of landscape ecological process and pattern in the course of area expansion. 相似文献
14.
There is a long history of recognising and interpreting discontinuous change—phase transitions—in urban systems. In this paper,
we use the aggregate retail model as an archetype to explore some new ideas. For example, we argue that the dependence of
paths of development on initial conditions has been understudied, and we offer a new graphical analysis that demonstrates
explicitly their influence on discrete change. We introduce an order parameter, and we plot this on a ‘results grid’ to facilitate
the discovery of possible phase transitions. We illustrate the use of these new developments with an application to London.
We show how retail developers can change the ‘initial conditions’ at a point in time and possibly bring about phase transitions
by their actions. This also shows that it should be possible to account for the history of urban development as a sequence
of initial conditions, illustrating path dependence. Secondly, the model could be deployed in relation to a new shopping zone,
and the tools developed here used to calculate the minimum size of a new development in order for it to compete. We explore
the ‘minimum size’ idea in relation to a new shopping zone in London. 相似文献
15.
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: |
16.
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: |
17.
Toshio Fukushima 《Journal of Geodesy》2006,79(12):689-693
By using Halley’s third-order formula to find the root of a non-linear equation, we develop a new iterative procedure to solve an irrational form of the “latitude equation”, the equation to determine the geodetic latitude for given Cartesian coordinates. With a limit to one iteration, starting from zero height, and minimizing the number of divisions by means of the rational form representation of Halley’s formula, we obtain a new non-iterative method to transform Cartesian coordinates to geodetic ones. The new method is sufficiently precise in the sense that the maximum error of the latitude and the relative height is less than 6 micro-arcseconds for the range of height, −10 km ≤ h ≤ 30,000 km. The new method is around 50% faster than our previous method, roughly twice as fast as the well-known Bowring’s method, and much faster than the recently developed methods of Borkowski, Laskowski, Lin and Wang, Jones, Pollard, and Vermeille. 相似文献
18.
P. Moore 《Journal of Geodesy》1987,61(3):223-234
Starlette was launched in 1975 in order to study temporal variations in the Earth’s gravity field; in particular, tidal and
Earth rotation effects. For the period April 1983 to April 1984 over12,700 normal points of laser ranging data to Starlette have been sub-divided into49 near consecutive 5–6 day arcs. Normal equations for each arc as obtained from a least-squares data reduction procedure, were
solved for ocean tidal parameters along with other geodetic and geodynamic parameters. The tidal parameters are defined relative
to Wahr’s body tides and Wahr’s nutation model and show fair agreement with other satellite derived results and those obtained
from spherical harmonic decomposition of global ocean tidal models. 相似文献
19.
Evaluation of the first GOCE static gravity field models using terrestrial gravity,vertical deflections and EGM2008 quasigeoid heights 总被引:1,自引:1,他引:0
Recently, four global geopotential models (GGMs) were computed and released based on the first 2 months of data collected
by the Gravity field and steady-state Ocean Circulation Explorer (GOCE) dedicated satellite gravity field mission. Given that
GOCE is a technologically complex mission and different processing strategies were applied to real space-collected GOCE data
for the first time, evaluation of the new models is an important aspect. As a first assessment strategy, we use terrestrial
gravity data over Switzerland and Australia and astrogeodetic vertical deflections over Europe and Australia as ground-truth
data sets for GOCE model evaluation. We apply a spectral enhancement method (SEM) to the truncated GOCE GGMs to make their
spectral content more comparable with the terrestrial data. The SEM utilises the high-degree bands of EGM2008 and residual
terrain model data as a data source to widely bridge the spectral gap between the satellite and terrestrial data. Analysis
of root mean square (RMS) errors is carried out as a function of (i) the GOCE GGM expansion degree and (ii) the four different
GOCE GGMs. The RMS curves are also compared against those from EGM2008 and GRACE-based GGMs. As a second assessment strategy,
we compare global grids of GOCE GGM and EGM2008 quasigeoid heights. In connection with EGM2008 error estimates, this allows
location of regions where GOCE is likely to deliver improved knowledge on the Earth’s gravity field. Our ground truth data
sets, together with the EGM2008 quasigeoid comparisons, signal clear improvements in the spectral band ~160–165 to ~180–185
in terms of spherical harmonic degrees for the GOCE-based GGMs, fairly independently of the individual GOCE model used. The
results from both assessments together provide strong evidence that the first 2 months of GOCE observations improve the knowledge
of the Earth’s static gravity field at spatial scales between ~125 and ~110 km, particularly over parts of Asia, Africa, South
America and Antarctica, in comparison with the pre-GOCE-era. 相似文献
20.
S. Saran R. Joshi S. Sharma H. Padalia V. K. Dadhwal 《Journal of the Indian Society of Remote Sensing》2010,38(3):535-547
The study explores the use of multiple criteria decision techniques in predicting spatial niche of Brown oak (also known as
Kharsu oak, Quercus semecarpifolia Sm.) formation in midaltitude (2,400–3,500 meter amsl) Kumaun Himalaya. Predictive models using various climatic and topographical
factors influencing Brown oak’s growth and survival were developed to define its current ecological niche. Analytical Hierarchical
Process (AHP) method involving Saaty’s pair-wise comparison was performed to rank the explanatory powers of each compared
variable. Variables were suitably weighted using fuzzy factor standardization scheme to reflect their relative importance
in defining species niche. An optimum indicator was then chosen for deriving a site suitability map of brown oak. This study
establishes the role of aspect in the current distribution of the species along with known influence of altitude. Future niches
of oak has been tracked in the projected climate change scenario of +1°C and +2°C rise in temperature and 20 mm in precipitation.
The results show that on predicted +1°C and +2°C increase in temperature, present habitat of brown oak distribution may be
reduced by 40 per cent and 76 per cent respectively. 相似文献