Tidal Systems and Reductions for Improvement of the Bulgarian National Vertical Reference System

Valcheva, S; Yovev, I; Grebenitcharsky, R

doi:10.1007/978-3-319-10837-7_33

Tidal Systems and Reductions for Improvement of the Bulgarian National Vertical Reference System

Lookup NU author(s): Stanislava Valcheva, Dr Rossen Grebenitcharsky

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Abstract

Although discussed worldwide, the application of tidal systems in the Bulgarian National Vertical Reference System is still in its initial steps. The information available in the papers and technical reports concerning the current tidal system and/or tidal reductions applied to different quantities is either vague or missing.The current paper shows the status of terrestrial gravity and levelling data in Bulgaria with respect to the tidal system. The differences between geopotential numbers and normal heights in mean and zero tidal system are examined. For data source, four levelling lines from the National First Order Levelling Network are used. In addition, a comparison between the calculated normal heights and the official data published in the "Catalogue of the National First Order Levelling Network Benchmarks in European Vertical Reference System 2007" is made. At the end of the paper, proposals for the proper choice of tidal system in the country are given, taking into account future international as well as local precise geodetic applications.