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1.
A new adjustment of the geodetic control networks in North America has been completed, resulting in a new continental datum—the
North American Datum of 1983 (NAD 83).
The establishment ofNAD 83 was the result of an international project involving the National Geodetic Survey of the United States, the Geodetic Survey
of Canada, and the Danish Geodetic Institute (responsible for surveying in Greenland). The geodetic data in Mexico and Central
America were collected by the Inter American Geodetic Survey and validated by the Defense Mapping Agency Hydrographic/Topographic
Center.
The fundamental task ofNAD 83 was a simultaneous least squares adjustment involving 266,436 stations in the United States, Canada, Mexico, and Central
America. The networks in Greenland, Hawaii, and the Caribbean islands were connected to the datum through Doppler satellite
and Very Long Baseline Interferometry (VLBI) observations.
The computations were performed with respect to the ellipsoid of the Geodetic Reference System of 1980. The ellipsoid is positioned
in such a way as to be geocentric, and its axes are oriented by the Bureau International de l'Heure Terrestrial System of
1984.
The mathematical model for theNAD readjustment was the height-controlled three-dimensional system. The least squares adjustment involved 1,785,772 observations
and 928,735 unknowns. The formation and solution of the normal equations were carried out according to the Helmert block method.
[Authors' note:This article is a condensation of the final report of the NAD 83 project. The full report (Schwarz,1989) contains a more complete discussion of all the topics.] 相似文献
2.
Vasilios K. Despotakis 《Journal of Geodesy》1989,63(4):342-358
This paper studies the use of two new methods for gravimetric geoid undulation computations: The Molodenskii's and Sjöberg's methods that both modify the original Stokes'function so that certainrms errors are minimized. These new methods were checked against the traditional methods of Stokes' and Meissl's modification with the criterion of the globalrms undulation error that each method implies. Sjöberg's method gave consistently the smallest globalrms undulation error of all the other methods for capsizes 0° to 10°. However with the exception of Stokes' method, for capsizes between 0° to 5°, all the methods gave approximately (within±5cm) the same globalrms undulation error. Actual gravity data within a cap of 2° and potential coefficient information were then combined to compute the undulation of 39 laser stations distributed around the world. Therms discrepancy between the gravimetric undulations using all the four methods and the undulations computed as the ellipsoidal minus the orthometric height of 28 at the above stations was±1.70,±1.65,±1.66,±1.65m for the Stokes', Meissl's, Molodenskii's and Sjöberg's method respectively. For five oceanic laser stations where no terrestrial gravity data was available, theGEOS-3/SEASAT altimeter sea surface heights were used to compute the undulations of these stations in a collocation method. Therms discrepancy between the altimeter derived undulation and the ellipsoidal mirus orthometric value of the undulation was ±1.30m for the above five laser stations. 相似文献
3.
Laser ranging to Starlette from April 1983 to April 1984 has been used to determine a coordinate set, UASC.ST1, of laser reference
points for 18 tracking stations. The coordinates were derived by application of the least-squares data reduction procedure
in a simultaneous solution along with geodynamic parameters for 49 near consecutive 5–6 day arcs. Comparisons with the University
of Texas station coordinates,LSC 8112 andLSC 8402, and theRGO, Herstmonceux, coordinates,RGOSC.LG2, reveal consistency to near 30 cm in each coordinate. Furthermore, the translation vectors of the comparisons are not significantly
different from zero indicating consistency in the implied origins of the systems.
The period of analysis included seven occasions in which STARLETTE was tracked near simultaneously by three or four laser
stations in North America. Using the short arcs as reference frameworks, station coordinates were determined by application
of two contrasting methods, namely, a multi-arc simultaneous analysis and a weighted mean of the individual pass solutions.
The former compared more favourably with baselines from the long-arc solution with anRMS error of near 16 cm. Comparison against theLSC 8402 coordinates confirmed that baselines accurate to within 15 cm can be achieved by satellite laser ranging to Starlette. 相似文献
4.
Based upon a data set of 25 points of the Baltic Sea Level Project, second campaign 1993.4, which are close to mareographic
stations, described by (1) GPS derived Cartesian coordinates in the World Geodetic Reference System 1984 and (2) orthometric
heights in the Finnish Height Datum N60, epoch 1993.4, we have computed the primary geodetic parameter W
0(1993.4) for the epoch 1993.4 according to the following model. The Cartesian coordinates of the GPS stations have been converted
into spheroidal coordinates. The gravity potential as the additive decomposition of the gravitational potential and the centrifugal
potential has been computed for any GPS station in spheroidal coordinates, namely for a global spheroidal model of the gravitational
potential field. For a global set of spheroidal harmonic coefficients a transformation of spherical harmonic coefficients
into spheroidal harmonic coefficients has been implemented and applied to the global spherical model OSU 91A up to degree/order
360/360. The gravity potential with respect to a global spheroidal model of degree/order 360/360 has been finally transformed
by means of the orthometric heights of the GPS stations with respect to the Finnish Height Datum N60, epoch 1993.4, in terms
of the spheroidal “free-air” potential reduction in order to produce the spheroidal W
0(1993.4) value. As a mean of those 25 W
0(1993.4) data as well as a root mean square error estimation we computed W
0(1993.4)=(6 263 685.58 ± 0.36) kgal × m. Finally a comparison of different W
0 data with respect to a spherical harmonic global model and spheroidal harmonic global model of Somigliana-Pizetti type (level
ellipsoid as a reference, degree/order 2/0) according to The Geodesist's Handbook 1992 has been made.
Received: 7 November 1996 / Accepted: 27 March 1997 相似文献
5.
The Global Positioning System,GPS, is widely used for time comparisons between distant laboratories. Over distances of the order of 1000km or less, the system has the capability of 1 to 2ns accuracy. However this requires a relative positioning with errors lower than 30cm. We show that this positioning can be derived from theGPS time comparisons themselves. An example for European laboratories is given. 相似文献
6.
Traditionally Inertial Surveying Systems (ISS) are used for missions of30 km to 100 km length. Today, a new type ofISS application is emanating from an increased need for survey control densification in urban areas often in connection with
land information systems or cadastral surveys.
The accuracy requirements of urban surveys are usually high. The loss in accuracy caused by the coordinate transfer betweenIMU and ground marks is investigated and an offsetting system based on electronic tacheometers is proposed.
An offsetting system based on a Hewlett-PackardHP 3820A electronic tacheometer has been tested in Sydney (Australia) in connection with a vehicle mountedLITTON Auto-Surveyor SystemII. On missions over750 m (8 stations,25 minutes duration,3.5 minuteZUPT intervals, mean offset distances 9 metres) accuracies of37 mm (one sigma) in position and8 mm in elevation were achieved. Some improvements to theLITTON Auto-Surveyor SystemII are suggested which would improve the accuracies even further. 相似文献
7.
Yehuda Bock Richard I. Abbot Charles C. Counselman III Robert W. King 《Journal of Geodesy》1986,60(3):241-254
By interferometric analysis ofGPS phase observations made at Owens Valley, Mojave, and Mammoth Lakes, California, we determined the coordinate components of the71–245–313 km triangle of baselines connecting these sites. A separate determination was made on each of four days, April 1–4, 1985. The satellite ephemerides used in these determinations had been derived from observations on other baselines. Therms scatters of the four daily determinations of baseline vector components about their respective means ranged from a minimum of6 mm for the north component of the71-km baseline to a maximum of34 mm for the vertical component of the245-km baseline. To test accuracy, we compared the mean of ourGPS determinations of the245-km baseline between Owens Valley and Mojave with independent determinations by others using very-long-baseline interferometry(VLBI) and satellite laser ranging(SLR). TheGPS-VLBI difference was within 2 parts in10 7 for every vector component. TheGPS-SLR difference was within6 parts in10 8 in the horizontal coordinates, but83 mm in height. 相似文献
8.
In November 1968, a marine geodetic control point was established in the Pacific Ocean at a water depth of6,200 feet. The control point (reference point) consists of three underwater acoustic transponders, two of which are powered with
lead-acid batteries and the third with an underwater radioisotope power source “URIPS” with a10- to20- year life expectancy. Four independent measuring techniques (LORAC airborne line-crossing, satellite, ship inertial, and
acoustic techniques) were used to measure and determine the coordinates of the control point. Preliminary analysis of the
acoustic and airborne data indicates that high accuracies can be achieved in the establishment of geodetic reference points
at sea. Geodetic adjustment by the method of variation of coordinates yielded a standard point error of±50 to±66 feet in determining the unknown ship station. The original location of the ship station as determined by shipboard navigation
equipment was off by about1,600 feet.
Paper previously published in the Proceedings of the Second Marine Geodesy Symposium of the Marine Technology Society. 相似文献
9.
Peter F. MacDoran 《Journal of Geodesy》1979,53(2):117-138
The satellites of the Global Positioning System (GPS) offer an important new geodetic resource making possible a highly accurate
portable radio geodetic system. A concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) makes use
of GPS radio transmissions without any satellite modifications. By employing the technique of very long baseline interferometry
(VLBI) and its calibration methods, 0.5 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to
200 km respectively, with only 2 hours of on-site data acquisition. The use of quasar referenced ARIES Mobile VLBI to establish
a sparse fundamental control grid will provide a basis for making SERIES GPS measurements traceable to the time-invariant
quasar directions. Using four SERIES stations deployed at previously established ARIES sites, allows the GPS satellite apparent
positions to be determined. These apparent positions then serve as calibrations for other SERIES stations at unknown locations
to determine their positions in a manner traceable to the quasars. Because this proposed radio interferometric configuration
accomplishes its signal detection by cross-correlation, there is no dependence upon knowledge of the GPS transmitted waveforms
which might be encrypted. Since GPS radio signal strengths are 105 stronger than quasar signals, a great reduction in telecommunications sophistication is possible which will result in an
order of magnitude less cost for a SERIES GPS station compared to a quasar based mobile VLBI system. The virtually all-weather
capability of SERIES offers cost-effective geodetic monitoring with applications to crustal dynamics and earthquake research. 相似文献
10.
Differential tracking of theGPS satellites in high-earth orbit provides a powerful relative positioning capability, even when a relatively small continental
U.S. fiducial tracking network is used with less than one-third of the fullGPS constellation. To demonstrate this capability, we have determined baselines of up to2000 km in North America by estimating high-accuracyGPS orbits and ground receiver positions simultaneously. The2000 km baselines agree with very long baseline interferometry(VLBI) solutions at the level of1.5 parts in10
8 and showrms daily repeatability of0.3–2 parts in10
8. The orbits determined for the most thoroughly trackedGPS satellites are accurate to better than1 m. GPS orbit accuracy was assessed from orbit predictions, comparisons with independent data sets, and the accuracy of the continental
baselines determined along with the orbits. The bestGPS orbit strategies included data arcs of at least one week, process noise models for tropospheric fluctuations, estimation
ofGPS solar pressure coefficients, and combined processing ofGPS carrier phase and pseudorange data. For data arcs of two weeks, constrained process noise models forGPS dynamic parameters significantly improved the solutions. 相似文献
11.
J. C. Bhattacharji 《Journal of Geodesy》1973,47(1):65-72
The method of converting geodetic coordinates from a national geodetic reference system into the standard Earth on having
known the geodetic coordinates of at least one station in common with the considered systems, is described in detail; the
orientation of the Standard Earth at the initial station of the national geodetic reference system, is also determined side
by side. For illustration, use has been made of the known coordinates of the Baker-Nunn station at Naini Tal, in India, being
in common with the Indian Everest Spheroid and the Smithsonian Institution Standard Earth C7 system (Veis, 1967). The method advocated is likely to be more precise than the existing ones as it does not assume the parallelism
of axes of reference between the Standard Earth and the national geodetic reference systems which may not necessarily hold
good in actual practice. 相似文献
12.
《测量评论》2013,45(30):457-462
AbstractIn the original geodetic series in Southern Rhodesia—completed by Mr Alexander Simms in 1901—the geographical coordinates of all stations were referred to the point SALISBURYas origin. The coordinates of SALISBURY were fixed by interchange of telegraphic signals with the Royal Observatory at the Cape for longitude, combined with astronomical determinations of time, latitude, and azimuth (see Vol. III, “Geodetic Survey of South Africa”). 相似文献
13.
Summary Various geodetic problems (the free nonlinear geodetic boundary value problem, the computation of Gauß-Krüger coordinates or UTM coordinates, the problem of nonlinear regression) demand theinversion of an univariate, bivariate, trivariate, in generalmultivariate homogeneous polynomial of degree n. The new algorithm which is oriented towardsSymbolic Computer Manipulation is based upon the algebraic power base computation with respect toKronecker-Zehfu product structure leading to the solution of a system oftriangular matrix equations: Only the first row of the inverse triangular matrix has to be computed. TheSymbolic Computer Manipulation program of the GKS algorithm is available from the authors. 相似文献
14.
C-D. Zhang H.T. Hsu X.P. Wu S.S. Li Q.B. Wang H.Z. Chai L. Du 《Journal of Geodesy》2005,79(8):413-420
The algorithm to transform from 3D Cartesian to geodetic coordinates is obtained by solving the equation of the Lagrange parameter.
Numerical experiments show that geodetic height can be recovered to 0.5 mm precision over the range from −6×106 to 1010 m.
Electronic Supplementary Material: Supplementary material is available in the online version of this article at 相似文献
15.
The initial value problem and the stability of solution in the determination of the coordinates of three observing stations
and four retro-reflectors by lunar laser ranging are discussed. Practical iterative computations show that the station coordinates
can be converged to about 1 cm, but there will be a slight discrepancy of the longitudinal components computed by various
analysis centers or in different years. There are several factors, one of which is the shift of the right ascension of the
Moon, caused by the orientation deviation of the adopted lunar ephemeris, which can make the longitudinal components of all
observing stations rotate together along the longitudinal direction with same angle. Additionally, the frame of selenocentric
coordinates is stable, but a variation or adjustment of lunar third-degree gravitational coefficients will cause a simultaneous
shift along the reflectors' longitudes or rotation around the Y axis.
Received: 21 August 1996 / Accepted: 17 November 1998 相似文献
16.
A least-squares prediction method is described to estimate horizontal coordinate distortions at lower order points of a network
using known coordinate differences (NAD27 coordinate distortions Δϕ′s and Δλ′s) at higher order points between NAD27 coordinates
and coordinates derived from a recent (MAY 76), relatively distortion free, adjustment of these points. Empirical autocovariance
functions of Δϕ and Δλ and crosscovariance function between Δϕ and Δλ are derived from some 5,250 data points and modelled
using series of exponential functions. Empirical mean square values of Δϕ and Δλ, which are a measure of the distortions in
NAD27 ϕ and λ, are 0.051 and 0.645 arcsecs2 respectively. The corresponding mean value of the product ΔϕΔλ, which is a measure of the correlation between Δϕ and Δλ,
is 0.056 arcsecs2. The accuracy obtainable for predicted Δϕ and Δλ at an arbitrary point (e.g., lower order station) is a function of the accuracy
and configuration of known Δϕ′s and Δλ′s in the surrounding area. Accuracies obtainable for various types of data configuration
are given. Under favorable conditions taking place in about 60% of cases, accuracies in terms of ms agreement with known values
of 0″.02 (0.6 m) and 0″.01 (0.2 m along parallel at latitude 50°) for the predicted latitude and longitude distortions are
obtainable. Finally, a comparison with a method based on the use of complex polynomials is made.
Presented at International Symposium on Geodetic Networks and Computations, Munich, August–September 1981. 相似文献
17.
《测量评论》2013,45(65):131-134
Abstract1. In geodetic work a ‘Laplace Point’ connotes a place where both longitude and azimuth have been observed astronomically. Geodetic surveys emanate from an “origin” O, whose coordinates are derived from astronomical observations: and positions of any other points embraced by the survey can be calculated on the basis of an assumed figure of reference which in practice is a spheroid formed by the revolution of an ellipse about its minor axis. The coordinates (latitude = ?, longitude = λ and azimuth = A) so computed are designated “geodetic”. 相似文献
18.
J. Feltens 《Journal of Geodesy》2008,82(8):493-504
Vector-based algorithms for the computation of azimuth, elevation and the ellipsoidal normal unit vector from 3D Cartesian
coordinates are presented. As a by-product, the formulae for the ellipsoidal normal vector can also be used to iteratively
transform rectangular Cartesian coordinates (X, Y, Z) into geodetic coordinates (φ, λ, h) for a height range from −5600 km to 108 km. Comparisons with existing methods indicate that the new transformation can compete with them. 相似文献
19.
An operational algorithm for computation of terrain correction (or local gravity field modeling) based on application of closed-form solution of the Newton integral in terms of Cartesian coordinates in multi-cylindrical equal-area map projection of the reference ellipsoid is presented. Multi-cylindrical equal-area map projection of the reference ellipsoid has been derived and is described in detail for the first time. Ellipsoidal mass elements with various sizes on the surface of the reference ellipsoid are selected and the gravitational potential and vector of gravitational intensity (i.e. gravitational acceleration) of the mass elements are computed via numerical solution of the Newton integral in terms of geodetic coordinates {,,h}. Four base- edge points of the ellipsoidal mass elements are transformed into a multi-cylindrical equal-area map projection surface to build Cartesian mass elements by associating the height of the corresponding ellipsoidal mass elements to the transformed area elements. Using the closed-form solution of the Newton integral in terms of Cartesian coordinates, the gravitational potential and vector of gravitational intensity of the transformed Cartesian mass elements are computed and compared with those of the numerical solution of the Newton integral for the ellipsoidal mass elements in terms of geodetic coordinates. Numerical tests indicate that the difference between the two computations, i.e. numerical solution of the Newton integral for ellipsoidal mass elements in terms of geodetic coordinates and closed-form solution of the Newton integral in terms of Cartesian coordinates, in a multi-cylindrical equal-area map projection, is less than 1.6×10–8 m2/s2 for a mass element with a cross section area of 10×10 m and a height of 10,000 m. For a mass element with a cross section area of 1×1 km and a height of 10,000 m the difference is less than 1.5×10–4m2/s2. Since 1.5× 10–4 m2/s2 is equivalent to 1.5×10–5m in the vertical direction, it can be concluded that a method for terrain correction (or local gravity field modeling) based on closed-form solution of the Newton integral in terms of Cartesian coordinates of a multi-cylindrical equal-area map projection of the reference ellipsoid has been developed which has the accuracy of terrain correction (or local gravity field modeling) based on the Newton integral in terms of ellipsoidal coordinates.Acknowledgments. This research has been financially supported by the University of Tehran based on grant number 621/4/859. This support is gratefully acknowledged. The authors are also grateful for the comments and corrections made to the initial version of the paper by Dr. S. Petrovic from GFZ Potsdam and the other two anonymous reviewers. Their comments helped to improve the structure of the paper significantly. 相似文献
20.
The problem of “global height datum unification” is solved in the gravity potential space based on: (1) high-resolution local
gravity field modeling, (2) geocentric coordinates of the reference benchmark, and (3) a known value of the geoid’s potential.
The high-resolution local gravity field model is derived based on a solution of the fixed-free two-boundary-value problem
of the Earth’s gravity field using (a) potential difference values (from precise leveling), (b) modulus of the gravity vector
(from gravimetry), (c) astronomical longitude and latitude (from geodetic astronomy and/or combination of (GNSS) Global Navigation
Satellite System observations with total station measurements), (d) and satellite altimetry. Knowing the height of the reference
benchmark in the national height system and its geocentric GNSS coordinates, and using the derived high-resolution local gravity
field model, the gravity potential value of the zero point of the height system is computed. The difference between the derived
gravity potential value of the zero point of the height system and the geoid’s potential value is computed. This potential
difference gives the offset of the zero point of the height system from geoid in the “potential space”, which is transferred
into “geometry space” using the transformation formula derived in this paper. The method was applied to the computation of
the offset of the zero point of the Iranian height datum from the geoid’s potential value W
0=62636855.8 m2/s2. According to the geometry space computations, the height datum of Iran is 0.09 m below the geoid. 相似文献