GPS receivers are often used in time-keeping applications, due to their availability, low price and high accuracy. We tested the capability of the GPS receiver to deliver a time-keeping accuracy needed for the time-critical applications, such as astrometry measurements, when a microsecond or better level of accuracy is needed in real-time. We tested a geodetic class GPS receiver against a rubidium standard, over a 24 hours period. In the overall view, the accuracy corresponds to the nominal values. However, we experienced outliers with the certain regularity that we could not explain with cycle-slips or the experiment set-up.
State surveys in a number of countries still use networks developed according to the principles that were applicable over 100 years ago or more. During that period, the rule was that the networks were developed in the classical geodetic datum, using the principle of relative positioning. Basic measured data were the angles and basis networks for scale definition, and measured data was not rectified to reflect the influence of physical parameters of the Earth (deflection of vertical). Given the types of measured values, reduction and positioning, these networks are called trigonometric and are divided into orders. The main network is 1st order and was used to develop networks of lower ranks-up to the point for details surveying. In the former Socialist Federal Republic of Yugoslavia trigonometric networks of the 1st order were developed in accordance with the recommendations of international organizations. We deliberately say "networks" because the 1st order trigonometric network of the former Yugoslavia was not developed as a single entity, but consisted of several parts. It is useful to know the history of the development and the accuracy of 1st order trigonometric networks because all surveys rely on this network, as the data obtained with new technology (GPS) is expected to fit into the existing system (Völgyesi in Transformation of Hungarian Unified National and Gauss-Krüger Projection System into WGS-84, Reports on Geodesy, 1997). The paper will present the historical facts relating to the development of 1st order trigonometric networks in the former Yugoslavia, without any analysis of the results of measurements and adjustment of individual parts of the network.
This paper presents the elements of metrology laboratory accreditation for calibration in the scope of calibration E-05 Dimensions, and calibration for the subject: the distance and angle measures. During the accreditation, but also in its maintenance, calibration laboratories must prove their competence. Each laboratory must have the quality management procedures for monitoring the validity of the calibrations performed. This monitoring shall be planned and reviewed through: internal quality control, participation in the interlaboratory comparisons or proficiency testing schemes, repeated calibrations using the same or different methods, re-calibration of the saved samples and correlation of results for different characteristics of the sample. According to the ISO/IEC 17025:2005 standard, competence is proved by participating in interlaboratory comparisons or participation in Proficiency testing (PT) schemes. This paper aims to stimulate discussion and debate about ways of proving competence of calibration laboratories. We believe that, in the interpretation of ISO/IEC 17025, the laboratory can demonstrate competence by participating in any activity, PT schemes or interlaboratory comparisons, and they are equal to this need. The procedure and the results of the interlaboratory comparisons between two accredited laboratories will be described.
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