The geodetic requirements for commercial data base management systems

There are many data base management systems now available as commercially marketed software packages. Although most of these packages were initially aimed at bussiness or administrative data processing applications, they may frequently also be the right tool for a scientific data processing task. This becomes more apparent as we notice that scientific computer programmers are spending more and more time on data management requirements rather than the coding of mathematical algorithms. In a scientific environment, a generalized data base management package is best viewed as a tool for programmers, rather than as a tool for direct, independent use by end users or by agency management. To the end user, the most attractive feature of a commerical DBMS is usually the interactive retrieval and update language. To the programmer, the most attractive feature is more likely to be the strong support for various types of keyed access. All of the manipulations necessary to build and maintain indices and other tables can be treated as procedural abstractions. Coupled with a procedural language, a DBMS offers the programmer a higher level (in the sense of more abstract) language. The most important geodetic requirement on a commercial DBMS is therefore that the package contain a strong Data Manipulation Language, with strong support for the algorithmic language used for scientific processing. Presented at International Symposium on Management of Geodetic Data, Copenhagen, August 24–26, 1981.     

Azimuth-dependent statistics for interpolating geodetic data

Most authors using statistical interpolation techniques on geodetic data have assumed isotropy for the undulation autocorrelation. Tests of actual data,414 deflections of the vertical, indicate this assumption is not valid. The results of interpolation, however, are not very sensitive to the parameters in the covariance function. A special limiting case for which statistical interpolation degenerates into a completely deterministic process is given in the spherical domain. In this case the covariance function has absolutely no effect on the results, so that the covariance of the output of a prediction need not be that assumed for the interpolation. This provides a self-correcting process whereby the information in the data corrects for a poor choice of covariance function. Estimates of the precision of the interpolation, on the other hand, are very sensitive to the covariance function, particularly to the modeling of azimuth dependence. A simple procedure for generalizing isotropic functions to azimuth dependence is given, which provides sufficiently accurate estimates of precision. The advisability of trend removal is illustrated by some numerical examples.     

大地测量数据标准分类研究与构建

针对大地测量数据标准在信息化大地测量生产、应用和服务过程中的重要性,本文详细研究了现代大地测量技术体系下的大地测量数据的内容、特点、分类原则以及分类方法,提出按照大地测量数据的专业特征、空间布局、数据时效、数据状态、数据类型、数据组织等特征从多个维度进行数据类别划分的方法,初步形成了大地测量数据内容框架标准体系,较好地满足了大地测量数据宏观逻辑组织和统一管理的数据标准要求.     

Estimating regional deformation from a combination of space and terrestrial geodetic data

We discuss an approach for efficiently combining different types of geodetic data to estimate time-dependent motions of stations in a region of active deformation. The primary observations are analyzed separately to produce loosely constrained estimates of station positions and coordinate system parameters which are then combined with appropriate constraints to estimate velocities and coseismic displacements. We define noninteger degrees of freedom to handle the case of finite constraints and stochastic perturbation of parameters and develop statistical tests for determining compatibility between different data sets. With these developments, we show an example of combining space and terrestrial geodetic data to obtain the deformation field in southern California. Received: 23 January 1997 / Accepted: 30 September 1997     

Estimation of Geodetic Parameters with VLBI Data of Last 5 Years

The meaning to research the potential of VLBI for geodetic applications is summarized. And the observation models and their related parameters of geodetic interest are investigated. Then, the principle and method of using the random model in VLBI data processing are investigated. With the world wide VLBI data from 2000-2004, the conditions to compute the parameters of geodetic interest are introduced, and so are the computing methods and processes. And the computed results of the parameters of geodetic interest are analyzed.     

Contemporary crustal velocity field in Alpine Mediterranean area of Italy from new geodetic data

A new crustal velocity field for the Alpine Mediterranean area was determined by using a time series spanning 6.5 years of 113 global navigation satellite system (GNSS) permanent stations. This area is characterized by a complex tectonic setting driven by the interaction of Eurasian and African plates. The processing was performed by using a state-of-the-art absolute antenna phase center correction model and by using recomputed precise International GNSS Service orbits, available since April 2014. Thus, a new and more accurate tropospheric mapping function for geodetic applications was adopted. Results provide a new detailed map of the kinematics throughout the entire study area. In some area of the Italian peninsula, such as in the central Apennines, the velocity vector orientation appears rotated with respect to previous results. These discrepancies suggest that the geodynamic setting of this sector of Mediterranean area should be revised in accordance with these new results.     

Prospect on Present-Day Crustal Kinematics and Dynamics Research in Sichuan-Yunnan Area with Geodetic Data

Combining the dense GPS and gravity observation data in Sichuan-Yunnan area, where there are the relatively complete active tectonic zones and seismic data, this paper applies the geodesy and geophysical inversion technique and the advanced numerical simulation to the synthesis study of geodesy inversion to find the dynamic process of tectonic movement and deformation in the area and finally to investigate the kinematics characteristic of the geological structure of different layer and different scale. This paper discusses the kinematics, dynamics model about the crustal movement of active blocks in Sichuan-Yunnan area and its adjacent areas.     

Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis

The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry (VLBI) results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9 and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [−3, 73] mm and a net scale increase of 0.3–0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply them in routine geodetic data analysis.     

Inertial survey systems in the geodetic arsenal

After reviewing the overall goals of geodesy, the paper focuses on the unique properties of inertial survey systems in the geodetic arsenal: three-dimensionality; ability to determine relative positions and changes in the anomalous components of the earth’s gravity field; and independence of line-of-sight observations and the effects of refraction, both traditional antagonists in geodetic operations. Inertial survey systems, including field and office computational procedures, are briefly reviewed. Their short-comings are pointed out and certain remedies offered. Future possible improvements in hardware and software, as well as the development of hybrid systems (e.g., with gravity gradiometers), are discussed. “Apart from the refinement of existing techniques through the use of computers and the introduction of electromagnetic and optical distance measurement devices, instrumental research and development has been conducted by scientists and engineers outside the geodetic profession. This separateness of geodetic instrument research and development is seen as a deficiency by some, because of the reduced interaction between measurement techniques and the problems to which they apply. However, geodesy does not seem extraordinarily different from other environmentally oriented sciences in this respect and certainly has been quick to adopt new techniques once the benefits become evident.” (NAS 1978, p. 6) From the Keynote Address presented at Second International Symposium on Inertial Technology for Surveying and Geodesy, June 1–5, 1981, Banff, Alberta, Canada.     

Application of the gravimetric method for a world geodetic system

It is desirable to unify the various unconnected geodetic systems of the world into a common earth-centered world datum. This can be achieved by gravimetric means. The gravimetric deflection components have been determined at a certain number of stations in different areas. Utilizing the differences between the gravimetric and astro-geodetic deflection components, the reduction of the major geodetic datums into a common world geodetic system has been accomplished. Geophysical Studies Section Aeronautical Chart and Information Center Presented at the Twelfth General Assembly of the International Union of Geodesy and Geophysics Helsinki, Finland     

The Iceland 1986 GPS geodetic survey: tectonic goals and data processing results

Summary The 1986 GPS survey of Iceland aimed to: (1) establish geodetic control in the South Iceland Seismic Zone (SISZ), to study destructive earthquakes there, (2) measure a country-wide network to form the basis of a new first order national network. 51 points were surveyed, with 20–30 km spacings within the SISZ and 100 km spacings elsewhere. The data were processed using the Bernese GPS software Version 3. Analysis was difficult due to poor satellite geometry and short-period ionospheric variations. However, an ambiguity-fixed, ionosphere-free solution gave accuracies of 1–2 cm in the horizontal and 2–3 cm in the vertical for the SISZ network and an ambiguity-free, ionosphere-free solution yielded accuracies of about 5 cm for the country-wide network. An ionosphere-free solution for the total survey with ambiguities fixed for the SISZ network only gave marginal additional improvements over the two separate solutions. GPS surveying has continued annually in Iceland with measurements in South Iceland in 1989 and 1992 (Hackman 1991; Sigmundsson 1992) and in North Iceland in 1987, 1990 and 1992 (Jahn et al. 1992; Foulger et al. 1992).     

Reducing the draconitic errors in GNSS geodetic products

Systematic errors at harmonics of the GPS draconitic year have been found in diverse GPS-derived geodetic products like the geocenter $Z$ -component, station coordinates, $Y$ -pole rate and orbits (i.e. orbit overlaps). The GPS draconitic year is the repeat period of the GPS constellation w.r.t. the Sun which is about 351 days. Different error sources have been proposed which could generate these spurious signals at the draconitic harmonics. In this study, we focus on one of these error sources, namely the radiation pressure orbit modeling deficiencies. For this purpose, three GPS+GLONASS solutions of 8 years (2004–2011) were computed which differ only in the solar radiation pressure (SRP) and satellite attitude models. The models employed in the solutions are: (1) the CODE (5-parameter) radiation pressure model widely used within the International GNSS Service community, (2) the adjustable box-wing model for SRP impacting GPS (and GLONASS) satellites, and (3) the adjustable box-wing model upgraded to use non-nominal yaw attitude, specially for satellites in eclipse seasons. When comparing the first solution with the third one we achieved the following in the GNSS geodetic products. Orbits: the draconitic errors in the orbit overlaps are reduced for the GPS satellites in all the harmonics on average 46, 38 and 57 % for the radial, along-track and cross-track components, while for GLONASS satellites they are mainly reduced in the cross-track component by 39 %. Geocenter $Z$ -component: all the odd draconitic harmonics found when the CODE model is used show a very important reduction (almost disappearing with a 92 % average reduction) with the new radiation pressure models. Earth orientation parameters: the draconitic errors are reduced for the $X$ -pole rate and especially for the $Y$ -pole rate by 24 and 50 % respectively. Station coordinates: all the draconitic harmonics (except the 2nd harmonic in the North component) are reduced in the North, East and Height components, with average reductions of 41, 39 and 35 % respectively. This shows, that part of the draconitic errors currently found in GNSS geodetic products are definitely induced by the CODE radiation pressure orbit modeling deficiencies.     

On the meaning of geodetic orientation

After deriving models for changes of coordinates and azimuths due to rotations, the investigation considers methods for modeling terrestrial orientation in adjustments of geodetic networks. If a misorientation of a geodetic network exists, this can be due to systematic errors in astronomic longitude or in astronomic azimuth, or in both. A separation of these two effects is not possible in practice. The initial azimuth at the datum origin contributes to the orientation only as much as any other azimuth of the same weight.     

Preliminary results of the establishment of a marine geodetic point in the Pacific Ocean

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.