共查询到20条相似文献，搜索用时 125 毫秒
1.
J. C. Owens 《Journal of Geodesy》1968,42(3):277-291
The development of lasers, new electro-optic light modulation methods, and improved electronic techniques have made possible
significant improvements in the range and accuracy of optical distance measurements, thus providing not only improved geodetic
tools but also useful techniques for the study of other geophysical, meteorological, and astronomical problems. One of the
main limitations, at present, to the accuracy of geodetic measurements is the uncertainty in the average propagation velocity
of the radiation due to inhomogeneity of the atmosphere. Accuracies of a few parts in ten million or even better now appear
feasible, however, through the use of the dispersion method, in which simultaneous measurements of optical path length at
two widely separated wavelengths are used to determine the average refractive index over the path and hence the true geodetic
distance. The design of a new instrument based on this method, which utilizes wavelengths of6328 ? and3681 ? and3 GHz polarization modulation of the light, is summarized. Preliminary measurements over a5.3 km path with this instrument have demonstrated a sensitivity of3×10
−9
in detecting changes in optical path length for either wavelength using1-second averaging, and a standard deviation of3×10
−7
in corrected length. The principal remaining sources of error are summarized, as is progress in other laboratories using
the dispersion method or other approaches to the problem of refractivity correction. 相似文献
2.
In satellite data analysis, one big advantage of analytical orbit integration, which cannot be overestimated, is missed in
the numerical integration approach: spectral analysis or the lumped coefficient concept may be used not only to design efficient
algorithms but overall for much better insight into the force-field determination problem. The lumped coefficient concept,
considered from a practical point of view, consists of the separation of the observation equation matrix A=BT into the product of two matrices. The matrix T is a very sparse matrix separating into small block-diagonal matrices connecting the harmonic coefficients with the lumped
coefficients. The lumped coefficients are nothing other than the amplitudes of trigonometric functions depending on three
angular orbital variables; therefore, the matrix N=B
T
B will become for a sufficient length of a data set a diagonal dominant matrix, in the case of an unlimited data string length
a strictly diagonal one. Using an analytical solution of high order, the non-linear observation equations for low–low SST range data can be transformed into a form to allow the application of the lumped concept.
They are presented here for a second-order solution together with an outline of how to proceed with data analysis in the spectral
domain in such a case. The dynamic model presented here provides not only a practical algorithm for the parameter determination
but also a simple method for an investigation of some fundamental questions, such as the determination of the range of the
subset of geopotential coefficients which can be properly determined by means of SST techniques or the definition of an optimal
orbital configuration for particular SST missions. Numerical results have already been obtained and will be published elsewhere.
Received: 15 January 1999 / Accepted: 30 November 1999 相似文献
3.
4.
E. Grafarend 《Journal of Geodesy》1970,44(1):41-49
Summary The probability to find an error vector in multiples of the Helmert-Maxwell-Boltzmann point error σ2 δij(δij Kronecker symbol) is calculated. It is found that the probability is for σ39%, for2 σ86% and for3 σ99% in two dimensions, for σ20%, for2 σ74% and for3 σ97% in three dimensions. The fundamental Maxwell-Boltzmann-distribution is tabulated0,02 (0,02) 4,50.
相似文献
5.
《测量评论》2013,45(23):53-54
AbstractThe problem of the influence of the paper itself on bearings taken off maps or plans has been recently discussed by G. T. M. in this Review (iii, 22, 479). The following alternative method of solving the problem may be of interest; the same figure and symbols are used as in the article mentioned. 相似文献
6.
E. Mittermayer 《Journal of Geodesy》1972,46(2):139-157
Summary The system of normal equations for the adjustment of a free network is a singular one. Therefore, a number of coordinates
has to be fixed according to the matrix. The mean square errors and the error ellipses of such an adjustment are dependent
on this choice.
This paper gives a simple, direct method for the adjustment of free networks, where no coordinates need to be fixed. This
is done by minimizing not only the sum of the squares of the weighted errorsV
T
PV=minimun but also the Euclidean norm of the vectorX and of the covariance matrixQ X
T
X=minimum trace (Q)=minimum This last condition is crucial for geodetic problems of this type. 相似文献
7.
Y. Kozai 《Journal of Geodesy》1968,42(3):355-357
From periodic variations of the orbital inclinations of three artificial satellites 1959Alpha 1, 1960Iota 2, and 1962Beta Mu 1 Love’s number of the earth and time lag of the bodily tide due to the friction are determined, respectively,0.29±0.03 and(10±5) minutes in time.
While the previous paper on the determination of Love’s number of the earth (Kozai, 1967) was in press, a minor error was
discovered in the Differential Orbit Improvement program(DOI) of the Smithsonian Astrophysical Observatory(SAO). Since the analysis was based on time-variations of the orbital inclinations which were derived by theDOI from precisely reduced Baker-Nunn observations, it is likely that the results in the previous paper was affected by the error
in theDOI. Therefore, the analysis is iterated by using the revisedDOI. Three satellites, 1959Alpha 1 (Vanguard 2), 1960Iota 2 (rocket ofEcho 1), and 1962Beta Mu 1 (Anna) (see Table 1) are adopted for determining Love’s number in the present paper. The satellite, 1959Eta, which was used in the previous paper, is not adopted here, since the inclination of this satellite shows irregular variations
unexplained. Instead of 1959Eta 1962Beta Mu 1 is adopted as orbital elements from precisely reduced Baker-Nunn observations have become available for a long interval of
time for this satellite. 相似文献
8.
R. H. Rapp 《Journal of Geodesy》1969,43(1):47-80
A set of2261 5°×5° mean anomalies were used alone and with satellite determined harmonic coefficients of the Smithsonian' Institution to determine
the geopotential expansion to various degrees. The basic adjustment was carried out by comparing a terrestrial anomaly to
an anomaly determined from an assumed set of coefficients. The (14, 14) solution was found to agree within ±3 m of a detailed geoid in the United States computed using1°×1° anomalies for an inner area and satellite determined anomalies in an outer area. Additional comparisons were made to the
input anomaly field to consider the accuracy of various harmonic coefficient solutions.
A by-product of this investigation was a new γE=978.0463 gals in the Potsdam system or978.0326 gals in an absolute system if −13.7 mgals is taken as the Potsdam correction. Combining this value of γE withf=1/298.25, KM=3.9860122·10
22
cm
3
/sec
2
, the consistent equatorial radius was found to be6378143 m. 相似文献
9.
10.
AbstractDerivation of areas on the earth's surface, whether graticular or globular, is not a merely academic investigation. It may be required for many practical purposes. In a wide sense such areas are required for geographical use. But nowadays geography has numerous ramifications. 相似文献
11.
A new global TEC model for estimating transionospheric radio wave propagation errors 总被引：4，自引：0，他引：4
Space-based navigation and radar systems operating at single frequencies of <10 GHz require ionospheric corrections of the
signal delay or range error. Because this ionospheric propagation error is proportional to the total electron content of the
ionosphere along the ray path, a user friendly TEC model covering global scale and all levels of solar activity should be
helpful in various applications. Since such a model is not available yet, we present an empirical model approach that allows
determining global TEC very easily. Although the number of model coefficients and parameters is rather small, the model describes
main ionospheric features with good quality. Presented is the empirical approach describing dependencies on local time, geographic/geomagnetic
location and solar irradiance and activity. The non-linear approach needs only 12 coefficients and a few empirically fixed
parameters for describing the broad spectrum of TEC variation at all levels of solar activity. The model approach is applied
on high-quality global TEC data derived by the Center for Orbit Determination in Europe (CODE) at the University of Berne
over more than half a solar cycle (1998–2007). The model fits to these input data with a negative bias of 0.3 TECU and a RMS
deviation of 7.5 TECU. As other empirical models too, the proposed Global Neustrelitz TEC
Model NTCM-GLis climatological, i.e. the model describes the average behaviour under quiet geomagnetic conditions. During severe space
weather events the actual TEC data may deviate from the model values considerably by more than 100%. A preliminary comparison
with independent data sets as TOPEX/Poseidon altimeter data reveals similar results for NeQuick and NTCM-GL with RMS deviations
in the order of 5 and 11 TECU (1 TECU = 1016 electrons/m2) for low and high-solar activity conditions, respectively. The more extended data base of ionosphere information that accumulates
in the coming years will help in further improving the set of coefficients of the model. 相似文献
12.
On the multivariate total least-squares approach to empirical coordinate transformations. Three algorithms 总被引：2，自引：1，他引：1
The multivariate total least-squares (MTLS) approach aims at estimating a matrix of parameters, Ξ, from a linear model (Y−E
Y
= (X−E
X
) · Ξ) that includes an observation matrix, Y, another observation matrix, X, and matrices of randomly distributed errors, E
Y
and E
X
. Two special cases of the MTLS approach include the standard multivariate least-squares approach where only the observation
matrix, Y, is perturbed by random errors and, on the other hand, the data least-squares approach where only the coefficient matrix
X is affected by random errors. In a previous contribution, the authors derived an iterative algorithm to solve the MTLS problem
by using the nonlinear Euler–Lagrange conditions. In this contribution, new lemmas are developed to analyze the iterative
algorithm, modify it, and compare it with a new ‘closed form’ solution that is based on the singular-value decomposition.
For an application, the total least-squares approach is used to estimate the affine transformation parameters that convert
cadastral data from the old to the new Israeli datum. Technical aspects of this approach, such as scaling the data and fixing
the columns in the coefficient matrix are investigated. This case study illuminates the issue of “symmetry” in the treatment
of two sets of coordinates for identical point fields, a topic that had already been emphasized by Teunissen (1989, Festschrift
to Torben Krarup, Geodetic Institute Bull no. 58, Copenhagen, Denmark, pp 335–342). The differences between the standard least-squares
and the TLS approach are analyzed in terms of the estimated variance component and a first-order approximation of the dispersion
matrix of the estimated parameters. 相似文献
13.
《The Cartographic journal》2013,50(1):89-90
AbstractWhilst it can be fairly stated that the post war years have seen an upsurge of interest in the design of maps as printed material, the same cannot be said of the treatment of maps for projection, whether by 35 mm slides or overhead methods. 相似文献
14.
《测量评论》2013,45(1):15-21
AbstractThe practice of issuing a certain proportion of each edition of small-scale maps mounted upon linen or other cloth is of long standing, and for many years there have been machines capable of mounting rolls of paper upon rolls of linen, the linen-backed product being finally cut up into sheets for printing. 相似文献
15.
《测量评论》2013,45(13):395-400
AbstractGeneral.—The two main causes bringing the Surveyor's work into association with that of the Town-Planning Engineer are development of new areas, arising from industrial, residential, or other necessity for expansion, and the replanning of congested or badly laid out districts in existing towns. The initiative in such schemes may come from a Local Authority, private enterprise, or public representations. 相似文献
16.
17.
《The Cartographic journal》2013,50(3):255-258
AbstractThe paper presents an overview the development of techniques in and uses of tactile mapping2 through the last fifty or so years. It provides both a background for the other papers in this issue,3 and an account of the current state of the art. It notes that cartography has almost as much to learn from tactile cartography as vice versa, and suggests possible routes and areas for future developments in tactile mapping and the education and care of blind and visually impaired people. 相似文献
18.
《测量评论》2013,45(63):20-24
AbstractThe shutter eyepiece is a device for eliminating the effects of personality in observations involving the timing of a moving star crossing graticule lines. It is of importance in longitude observations and in any mixed observations involving timing of star passages over cross-lines—vertical, horizontal or oblique. 相似文献
19.
O. Remmer 《Journal of Geodesy》1969,43(2):99-122
A method for filtering of geodetic observationwhich leaves the final result normally distributed, is presented. Furthermore, it is shown that if you sacrifice100.a% of all the observations you may be (1−β).100% sure that a gross error of the size Δ is rejected.
Another and, may be intuitively, more appealing method is presented; the two methods are compared and it is shown why Method
1 should be preferred to Method 2 for geodetic purposes.
Finally the two methods are demonstrated in some numerical examples. 相似文献
20.
《测量评论》2013,45(24):68-69
AbstractThe following points occurred to me when reading the interesting paper on crustal equilibrium in E.S.R. No. 23. The principle of compensation or isostasy necessarily involves the idea of two different kinds of rock structure—one strong, the other weak or in extreme cases fluid; for example, there is the familiar case of the strong iceberg resisting change of shape in the liquid sea. In dealing with crustal problems of the earth then, we should make up our minds which part is to be considered as strong, e.g. the granite crust, and which part as weak or fluid, e.g. material at a depth x km. (say roo km.); by weak or fluid I mean that a possibility exists of horizontal movement. 相似文献