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Comparison of linear regression method and GMDH neural network in predicting the UTC(PL) national timescale DOI:10.15199/48.2018.11.01

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Predicting the UTC(k) local timescales is required in order to ensure the highest possible compliance of this scale with the UTC scale, called Coordinated Universal Time. The necessity of predicting a timescale results from the delay in the publication by the International Bureau of Weights and Measures BIPM (the French for Bureau International des Poids et Mesures) the values of [UTC - UTC(k)] deviations for individual UTC(k), which define the divergence of UTC(k) in relation to the UTC. These deviations are determined once a month as average values per day on Modified Julian Date MJD days ending with digits 4 and 9. The process of calculating UTC scale is very complex and time-consuming [1]. It requires a collection and proper preparation of measurement data from local and remote comparisons of over 400 atomic clocks sent to BIPM by a National Metrological Institutes NMIs [1], which carry out the physical implementation of the UTC(k) scale on the basis of commercial caesium clocks or hydrogen masers. This results in a delay in issuing the BIPM “Circular T" bulletin containing determined values of deviations for UTC(k), which is published between about 7th and 17th day of the following month. In this case, the time horizon of the first prediction is within 10 to 20 days. Delay in publication of the [UTC - UTC(k)] deviations by the BIPM adversely affect the result of prediction process of UTC(k) local timescale, and consequently on maintaining the best convergence of the UTC(k) with the UTC. For this purpose the BIPM has launched in 2012 a project called “A Rapid UTC" [1, 2], which main task is to expedite the transfer of information about the differences of the UTC(k) in relation to the UTC. On the basis of UTC Rapid scale, every Wednesday on the BIPMs ftp server the [UTCr - UTC(k)] deviations determined for the previous week are published, for each clock realizing the UTC(k) scale. This allows to shorten the [...]

Application of the GMDH neural networks in prediction of corrections of the national time scale


  The Polish time scale UTC(PL) is a local realization of the Universal Coordinated Time. The UTC is calculated as a weighted mean on the basis of constant comparisons of the atomic clocks located in numerous countries worldwide. The UTC(PL) is realized at the COM with the use of a selected HP5071A type cesium-beam atomic clock and a control device (microphasestepper), which provides introduction of corrections for the purpose of as good compatibility of the UTC(PL) with the UTC. The corrections for the UTC(PL) are set by the BIPM at the interval of five days. The values of such corrections for a given month are published by the BIPM in the bulletin of the “Circular T" series for the dates of the MJD (Modified Julian Date) ending with the digits 4 and 9. The problem of maintaining as good compliance of the UTC(PL) with the UTC as possible results from the significant delay in issuing the “Circular T" bulletin. It is available approximately on the 10th day of the following month. In such a case, the sole possible remedy is to predict the value of corrections for the following month. The learning process of the networks and predictions of the corrections for a given month are based upon the corrections published by the BIPM in the previous months and the results of the comparison of the clock which realizes the national atomic time scale for the same period of time with the UTC(PL). In the COM, the corrections are predicted on the basis of the regression line method [1] which, as suggested in the paper [6], may be extended by stochastic differential equations. In collaboration with the COM, the Institute of Electrical Metrology of the University of Zielona Góra has been running research on the application of the neural networks in predicting [...]

Predicting corrections for the UTC(PL) based on the UTC Rapid scale


  The time scales TAI and UTC are the designated scales at the International Bureau of Weights and Measures (BIP M, fr. Bureau International des Poids et Mesures), based on the measurement data obtained from local and remote comparison of several hundred atomic clocks from 70 time and frequency laboratories located around the world [2]. This means that the TAI and UTC scales are not physical time scales. In 1975 the General Conference on Weights and Measures recommended that the basis for determining the local time in each country was the atomic time UTC shifted by the total number of hours corresponding to the local time zone. Such arrangements provide a guarantee of uniformity among timing systems. Local time scales, sometimes called UTC (k), are physical realizations of UTC by National Metrology Institutes (NMIs). Officially in Poland since 2004, this has been the function of the Central Office of Measures (GUM, pl. Główny Urząd Miar), which maintains the scale of UTC (PL). UTC (k)s form a basis for mapping the units of measurement of time and frequency, and the designation of the official time in the country. The GUM, as with most of the NMIs implementing national time scales UTC (k), uses commercial cesium atomic clocks HP 5071A (now Symmetricom 5071A), which are characterized by an accuracy of 10-12 and a stability of 10-14. This ensures the highest stability of the UTC (k) and its compliance with UTC and enables the establishment of a metrologically reliable reference for time and frequency measurements in the country. This forces an appropriate correction to be made on the output signal of the UTC (k) generation system by the control device (microphase - stepper) [2]. A part of the system which executes UTC (PL) is presented in Figure 1, station 1, where F. D. is a frequency divider.The actual corrections of the UTC (k) in relation to UTC are determined by post-processing of the five-day intervals by the BIP M. So far, [...]

Application of neural networks for predicting selected time scales on the basis of UTC and UTCr scales DOI:10.15199/48.2016.10.58

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The paper presents research results on predicting the [UTC - UTC(k)] deviations by the means of GMDH-type neural network and data prepared in the form of time series built on the basis of [UTC - UTC(k)] and [UTCr - UTC(k)] deviations for the Austrian Timescale UTC(BEV) and the Lithuanian Timescale UTC(LT). The obtained results confirmed the possibility of applying the UTC Rapid scale for predicting the [UTC - UTC(k)] deviations by the means of GMDH-type neural network. Streszczenie. W pracy przedstawiono wyniki badań nad prognozowaniem odchyleń [UTC - UTC(k)] przy użyciu sieci neuronowej typy GMDH i danych przygotowanych w formie szeregu czasowego, zbudowanego na podstawie wartości odchyleń [UTC - UTC(k)] oraz [UTCr - UTC(k)], dla Austriackiej Skali Czasu UTC(BEV) oraz Litewskiej Skali Czasu UTC(LT). Otrzymane wyniki badań potwierdziły możliwość zastosowania skali UTC Rapid do prognozowania odchyleń [UTC - UTC(k)] w oparciu o sieci neuronowe typu GMDH. (Zastosowanie sieci neuronowych do prognozowania wybranych skal czasu na podstawie skal UTC i UTCr). Keywords: UTC(k) timescale, atomic clock, predicting [UTC - UTC(k)], GMDH neural network. Słowa kluczowe: skala czasu UTC(k), zegar atomowy, prognozowanie [UTC - UTC(k)], sieci neuronowe GMDH. Introduction National Metrology Institutes NMI conduct physical realizations of local time scales UTC(k), which in most cases are realized by commercial cesium clocks or active hydrogen masers. International UTC scale, called Coordinated Universal Time, is determined by the International Bureau of Weights and Measures BIPM (fr. Bureau International des Poids et Mesures). The process of calculating the UTC scale is very complex and timeconsuming. It requires a collection and proper preparation of measurement data from local and remote comparisons of more than 400 atomic clocks sent by an NMI [1] and the calculation of the UTC scale by BIPM. This results in a delay in issuing the BIPM "Circular T" [...]

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