共查询到20条相似文献,搜索用时 412 毫秒
1.
This study investigates the potential of multi-temporal signature analysis of satellite imagery to map rice area in South
24 Paraganas district of West Bengal. Two optical data (IRS ID LISS III) and three RADARSAT SAR data of different dates were
acquired during 2001. Multi-temporal SAR backscatter signatures of different landcovers were incorporated into knowledge based
decision rules and kharif landcover map was generated. Based on the spectral variation in signature, the optical data acquired
during rabi (January) and summer (March) season were classified using supervised maximum likelihood classifier. A co-incidence
matrix was generated using logical approach for a combined “rabi-summer” and “kharif-rabi-summer” landcover mapping. The major
landcovers obtained in South 24 Paraganas using remote sensing data are rice, water, aquaculture ponds, homestead, mangrove,
and urban area. The classification accuracy of rice area was 98.2% using SAR data. However, while generating combined “kharif-rabi-summer”
landcovers, the classification accuracy of rice area was improved from 81.6% (optical data) to 96.6% (combined SAR-Optical).
The primary aim of the study is to achieve better accuracy in classifying rice area using the synergy between the two kinds
of remotely sensed data. 相似文献
2.
Arcsecond-level accuracy of NASA's ICESat (Ice, Cloud, and land Elevation Satellite) satellite laser altimeter beam pointing
angle is required to satisfy the scientific goal of detecting centimeter-level elevation changes, over time, in the Greenland
and Antarctic ice sheets. Two different approaches, termed “topographic inferred” and “direct detection”, were examined for
calibrating the laser pointing angle (that is, detecting and removing pointing determination bias) at the 1.5-arcsec level,
using information independent of the onboard pointing instrumentation. Both approaches entail estimating the beam pointing
by differencing the three-dimensional position of the altimeter instrument and the laser-beam spot (or “footprint”) location
on the ground. Analytical assessments of the two approaches are discussed, along with recommendations for the ICESat pointing
determination calibration strategy.
Received: 28 April 2000 / Accepted: 6 November 2000 相似文献
3.
J. A. Weightman 《Journal of Geodesy》1967,41(3):237-247
Summary A datum change between two geodetic systems with points in common may be derived in three stages; slight adjustments of coordinates
to make the networks of common points geometrically similar in the two systems; a scale factor to make them geometrically
congruent; finally, an orthogonal transformation to swing them into coincidence.
The geometrical concept is developed of a “datum screw”, not arbitrarily chosen as is the “origin” or “datum point” of a geodetic
survey, but intrinsic to the geometry. The conditions under which it degenerates to a simple “datum shift” are discussed.
Differential and other formulae for changes of spheroid and of datum are given, together with a set of tables of coefficients. 相似文献
4.
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
5.
C. C. Tscherning 《Journal of Geodesy》1978,52(1):85-92
The term “entity” covers, when used in the field of electronic data processing, the meaning of words like “thing”, “being”,
“event”, or “concept”. Each entity is characterized by a set of properties.
An information element is a triple consisting of an entity, a property and the value of a property. Geodetic information is
sets of information elements with entities being related to geodesy. This information may be stored in the form ofdata and is called ageodetic data base provided (1) it contains or may contain all data necessary for the operations of a particular geodetic organization, (2)
the data is stored in a form suited for many different applications and (3) that unnecessary duplications of data have been
avoided.
The first step to be taken when establishing a geodetic data base is described, namely the definition of the basic entities
of the data base (such as trigonometric stations, astronomical stations, gravity stations, geodetic reference-system parameters,
etc...).
Presented at the “International Symposium on Optimization of Design and Computation of Control Networks”, Sopron, Hungary,
July 1977. 相似文献
6.
H. Wolf 《Journal of Geodesy》1980,54(1):45-53
Summary In a combined Doppler and terrestrial net adjustment not only the known systematic discrepancies in scale and orientation
between the Doppler measurements and the terrestrial results must be modelled, but also all available informations about the
accuracy of these systematic differences are to be taken into account. Using the Helmert-block method for the combination
procedure, no covariance matrices for the terrestrially determined coordinates must be computed, their numerical evaluation
being a computational detour. The proposed procedure as applied to real nets, includes all different kinds of geometric or
physical models, whereby their specific parameters are eliminated at this level. Two solutions are discussed, a three-dimensional
and a two-dimensional one, but “two-dimensional” is not equivalent to “non-spatial” in this context. 相似文献
7.
Atmospheric delays are contributors to the GNSS error budget in precise GNSS positioning that can reduce positioning accuracy
considerably if not compensated appropriately. Both ionospheric and tropospheric delay corrections can be determined with
help of reference stations in active GNSS networks. One approach to interpolate these error terms to the user’s location that
is employed in Germany’s SAPOS network is the determination of area correction parameters (ACP, German: “Fl?chenkorrekturparameter—FKP”).
A 2D interpolation scheme using data from at least 3 reference stations surrounding the rover is employed. A modification
of this method was developed which only makes use of as few as 2 reference stations and provides 1D linear correction parameters
along a “corridor” in which the user’s rover is moving. We present the results of a feasibility study portraying results from
use of corridor correction parameters for precise RTK-like positioning. The differences to the reference coordinates (3D)
attained in average for 1 h of data employing selected network nodes in Germany are between 0.8 and 2.0 cm, which compares
well with the traditional area correction method that yields an error of 0.7 up to 1.1 cm. 相似文献
8.
GNSS data management and processing with the GPSTk 总被引:2,自引:0,他引:2
Dagoberto Salazar Manuel Hernandez-Pajares Jose M. Juan Jaume Sanz 《GPS Solutions》2010,14(3):293-299
We organize complex problems in simple ways using a GNSS data management strategy based on “GNSS Data Structures” (GDS), coupled
with the open source “GPS Toolkit” (GPSTk) suite. The code resulting from using the GDS and their associated “processing paradigm”
is remarkably compact and easy to follow, yielding better code maintainability. Furthermore, the data abstraction allows flexible
handling of concepts beyond mere data encapsulation, including programmable general solvers. An existing GPSTk class can be
modified to achieve the goal. We briefly describe the “GDS paradigm” and show how the different GNSS data processing “objects”
may be combined in a flexible way to develop data processing strategies such as Precise Point Positioning (PPP) and network-based
PPP that computes satellite clock offsets on-the-fly. 相似文献
9.
The upward-downward continuation of a harmonic function like the gravitational potential is conventionally based on the direct-inverse
Abel-Poisson integral with respect to a sphere of reference. Here we aim at an error estimation of the “planar approximation”
of the Abel-Poisson kernel, which is often used due to its convolution form. Such a convolution form is a prerequisite to
applying fast Fourier transformation techniques. By means of an oblique azimuthal map projection / projection onto the local
tangent plane at an evaluation point of the reference sphere of type “equiareal” we arrive at a rigorous transformation of
the Abel-Poisson kernel/Abel-Poisson integral in a convolution form. As soon as we expand the “equiareal” Abel-Poisson kernel/Abel-Poisson
integral we gain the “planar approximation”. The differences between the exact Abel-Poisson kernel of type “equiareal” and
the “planar approximation” are plotted and tabulated. Six configurations are studied in detail in order to document the error
budget, which varies from 0.1% for points at a spherical height H=10km above the terrestrial reference sphere up to 98% for points at a spherical height H = 6.3×106km.
Received: 18 March 1997 / Accepted: 19 January 1998 相似文献
10.
The part of central west coast (Maharashtra and Goa) of India has been classified and quantified for coastal wetlands using LANDSAT data of 1985-86. The classification accuracy of the maps and area estimates achieved was 84% at 90% confidence level and the planimetric accuracy at 1:2,50,000 scale was 0.3 mm. The total coastal wetland areas in Maharashtra and Goa, have been estimated to be 1567 and 115 km:2, respectively. The estuarine and backwater regions contribute 44.6% of the wetland, followed by open mudflats (32%), mangroves (8.8%) and beach/spit (7.8%). Mangroves comprised of 17 species and are dominated by Rhizophora mucronata, Avicennia officinalis, A. marina, Sonneralia alba, Excoecaria agallocha and Acanthus ilicifolius. The sand-dune flora comprised of 63 species while rocky intertidal regions harboured > 100 species of marine algae. Erosional changes have been noticed to be predominant along the Maharashtra coast while progradation of beaches is noticed in Goa. 相似文献
11.
József Ádám 《Journal of Geodesy》1982,56(3):180-195
The Euclidean spaces with their inner products are used to describe methods of least squares adjustment as orthogonal projections
on finite-dimensional subspaces. A unified Euclidean space approach to the least squares adjustment methods “observation equations”
and “condition equations” is suggested. Hence not only the two adjustment solutions are treated from the view-point of Euclidean
space theory in a unified frame but also the existing duality relation between the methods of “observation equations” and
“condition equations” is discussed in full detail. Another purpose of this paper is to contribute to the development of some
familiarity with Euclidean and Hilbert space concepts. We are convinced that Euclidean and Hilbert space techniques in least
squares adjustment are elegant and powerful geodetic methods. 相似文献
12.
Assessing the carbon sequestration potential of subtropical pine forest in north-western Himalayas — A GIS approach 总被引:1,自引:0,他引:1
The present investigation was carried out to determine carbon sequestration potential of Solan Forest Division of Himachal
Pradesh during 2006–2007. There are six land uses viz., Chir pine, Ban oak, Deodar, Other broadleaves, Culturable and Un-culturable,
which are distributed in 538 compartments along altitudinal gradient from 900 to 2,100m. The study reveals that among various
land uses, the Other broadleaved species will result in maximum expected carbon (19.88 Mt) which will be 28.81, 23.95, and
3.07 times higher than standing carbon in Ban oak, Deodar and Chir pine, respectively. The Solan Forest Division on the whole,
has potential to sequester 17 times more carbon over standing carbon of 1.67 Mt, if forest species are extended to their corresponding
altitudinal limits in the “land area available for planting” i.e., Uncultrable land area in the forest division however, to
have an accurate estimate of the carbon sequestration potential of the area, other attributes that decides the establishment
of plantation of different species such as slope, aspect, soil, climate, etc. need to be taken into consideration beside altitude. 相似文献
13.
Selectivity estimation is crucial for query optimizers choosing an optimal spatial execution plan in a spatial database management system.This paper presents an Annular Bucket spatial histogram(AB histogram)that can estimate the selectivity in finer spatial selection and spatial join operations even when the spatial query has more operators or more joins.The AB histogram is represented as a set of bucket-range,bucket-count value pairs.The bucket-range often covers an annular region like a sin-gle-cell-sized photo frame.The bucket-count is the number of objects whose Minimum Bounding Rectangles(MBRs)fall between outer rectangle and inner rectangle of the bucket-range.Assuming that all MBRs in each a bucket distribute evenly,for every buck-et,we can obtain serial probabilities that satisfy a certain spatial selection or join conditions from the operations’ semantics and the spatial relations between every bucket-range and query ranges.Thus,according to some probability theories,spatial selection or join selectivity can be estimated by the every bucket-count and its probabilities.This paper also shows a way to generate an updated AB histogram from an original AB histogram and those probabilities.Our tests show that the AB histogram not only supports the selectivity estimation of spatial selection or spatial join with "disjoint","intersect","within","contains",and "overlap" operators but also provides an approach to generate a reliable updated histogram whose spatial distribution is close to the distribution of ac-tual query result. 相似文献
14.
Pramila Raina 《Journal of the Indian Society of Remote Sensing》1994,22(3):169-181
In the present study efforts have been made to identify and map areas affected by various land degradation processes with the aid of Landsat TM imagery data of 1988 and ground truth verification. The kind, extent and degree of land degradation have been mapped. In an area of over 4,124 sq. km. 51% was affected by water erosion and 30% area by wind erosion. Nearly 1.14% area is affected by salinity. Degradation due to combined effect of water and wind erosion and water erosion and salinization has affected 8.20% of the study area. 1.53% area is free from any hazard. Remaining 7.85% area comes under hills and rivers. Nearly 44 percent of the affected area is subjected to moderate and severe degradation which can easily be combatted by techniques referred. 相似文献
15.
A. Sakuma 《Journal of Geodesy》1963,37(3):249-260
Résumé L'état actuel des études préliminaires d'une mesure absolue de g au B.I.P.M. basée sur le principe de la “méthode des deux
stations” [1] est résumé dans cette note.
Une précision de g plus élevée que celle qui a été obtenue jusqu'à présent, est espérée à cause des avantages des mesures
symétriques dans cette méthode et des observations interférentielles des passages d'un corps lancé (un trièdre formé de trois
miroirs orthogonaux) à des stations fixes.
Nous envisageons qu'une précision de g de l'ordre de 0,1 mgal sera réalisable avec cette méthode.
Summary In this note, the present stage is outlined in the preparations for an absolute determination of gravity at B.I.P.M., based on the principle of “La méthode des deux stations” [1] (or so called “The up and down motion method”). It is expected that a value of g of greater accuracy than previous measurements will be obtained, due to the use of the symmetrical measurements by this principle and the use of the interferometric observations of the passage of the projected body (a corner cube reflector) in free fall across fixed horizontal stations. It seems probable that an accuracy of the order of 0.1 mgal will be obtained by this method.相似文献
16.
Change of river channel and bank erosion of the burhi dihing river (assam), assessed using remote sensing data and gis 总被引:1,自引:0,他引:1
The Burhi Dining river flows in a meandering course for about 220 km through alluvial plains of Assam including a short rocky
and hilly tract in between. Sequential changes in the position of banklines of the river due to consistent bank erosion have
been studied from Survey of India topographic maps of 1934 and 1972, and digital satellite data of 2001 and 2004 using GIS.
Two broad kinds of changes have been observed, e.g. alteration of direction of flow due to neck cut-off and progressive gradual
change of the meander bends that accounts for translational, lateral, rotational, extensional and other types of movement
of the meander bends. Study of bankline shift due to the bank erosion has been carried out for the periods 1934–1972, 1972–2001,
2001–2004 and 1934–2004 at 13 segments spaced at 5′ longitude interval (average 15 km) as the river course trends nearly east
to west. The amounts of the bank area lost due to erosion and gained due to sediment deposition are estimated separately.
The total area eroded in both banks during 1934–1972 was more (26.796 km2) as compared to sediment deposition (19.273 km2), whereas total sediment deposition was more (34.61 km2) during 1972-2001 as compared to erosion (23.152 km2). Erosion was again more in 2001–2004 (7.568 km2) as compared to sediment deposition (2.493 km2). During the entire period (1934–2004) of study the overall erosion on the both banks was 31.169 km2 and overall sediment deposition was 30.101 km2. The highest annual rates of bank erosion as well as bank building of the river are 21055.47 m2/km in 2001–2004 and 9665.81 m2/km in 1972-2001, respectively. Similarly the highest average annual rates of erosion as well as sediment deposition in both
banks are observed during 2001–2004 and 1972–2001, respectively. The hard rocks of the hilly tract situated in between result
in development of entrenched meandering and this tract has suffered minimum bank erosion. 相似文献
17.
Generalization of total least-squares on example of unweighted and weighted 2D similarity transformation 总被引:5,自引:2,他引:3
Frank Neitzel 《Journal of Geodesy》2010,84(12):751-762
In this contribution it is shown that the so-called “total least-squares estimate” (TLS) within an errors-in-variables (EIV)
model can be identified as a special case of the method of least-squares within the nonlinear Gauss–Helmert model. In contrast
to the EIV-model, the nonlinear GH-model does not impose any restrictions on the form of functional relationship between the
quantities involved in the model. Even more complex EIV-models, which require specific approaches like “generalized total
least-squares” (GTLS) or “structured total least-squares” (STLS), can be treated as nonlinear GH-models without any serious
problems. The example of a similarity transformation of planar coordinates shows that the “total least-squares solution” can
be obtained easily from a rigorous evaluation of the Gauss–Helmert model. In contrast to weighted TLS, weights can then be
introduced without further limitations. Using two numerical examples taken from the literature, these solutions are compared
with those obtained from certain specialized TLS approaches. 相似文献
18.
The resolution of a nonlinear parametric adjustment model is addressed through an isomorphic geometrical setup with tensor
structure and notation, represented by a u-dimensional “model surface” embedded in a flat n-dimensional “observational space”.
Then observations correspond to the observational-space coordinates of the pointQ, theu initial parameters correspond to the model-surface coordinates of the “initial” pointP, and theu adjusted parameters correspond to the model-surface coordinates of the “least-squares” point
. The least-squares criterion results in a minimum-distance property implying that the vector
Q must be orthogonal to the model surface. The geometrical setup leads to the solution of modified normal equations, characterized
by a positive-definite matrix. The latter contains second-order and, optionally, thirdorder partial derivatives of the observables
with respect to the parameters. This approach significantly shortens the convergence process as compared to the standard (linearized)
method. 相似文献
19.
Fabio Crosilla 《Journal of Geodesy》1983,57(1-4):226-239
This paper proposes an original method of constructing a criterion matrix for the optimal design of control networks by means
of the contraction of the eigenvalues and the rotation of the eigenvectors of a covariance matrix. The rotation of the eigenvectors
is carried out by two different methods, that is through independent rotations of the pairs of the eigenvector matrix components
and through a procrustean transfomation of the same matrix. The required criterion is that the “essential eigenvector components”
must be as orthogonal as possible to the predicted direction of deformation. A Second Order Design problem is then resolved,
that is the optimization of the precision of the observations of a local free distance network to be constructed for the study
of recent crustal movements in the seismogenetic area of Friuli (Italy). The results obtained show a high degree of correspondence
for the two proposed methods of rotation if limited rotations of the eigenvectors are considered. 相似文献
20.
M. Louis 《Journal of Geodesy》1975,49(1):110-111
Sans résumé
“Astronomy of star positions:A critical investigation of star catalogues, the methods of their construction and their purpose” by Heinrich Eichhorn 1 volume. 357 pages, 25 U.S. $, publié par Frederick Ungar Publishing Co, Inc., 250 Park Avenue South, New York, N.Y. 10003相似文献