Scholarly record
COMPARATIVE ANALYSIS OF LOCAL QUASI-GEOID MODELS APPLICATION IN BULGARIA THROUGH DIRECT GNSS AND LEVELLING MEASUREMENTS
Abstract
This paper is focused on the verification of two quasi-geoid models for the territory of Bulgaria (the model integrated into the Geodesy, Cartography and Cadastre Agency (GCCA) official product for the transformation of geodetic data and a model derived using the GNSS/levelling method) through direct geodetic measurements. The study was developed in the framework of the current 5th cycle of the 1st Order National Levelling Network (NLN), conducted in accordance with the requirements of the new 2021 Instruction [1]. This regulatory framework defines current standards for precise levelling measurements and determinations for the implementation of the European Vertical Reference System (EVRS) in Bulgaria [2]. Furthermore, this 2021 Instruction regulates the performance of GNSS determinations on levelling benchmarks with specified accuracy, which is essential for the subsequent use of data from direct measurements along levelling lines (geometric levelling, gravimetric and GNSS determinations); this enables subsequent modelling of the gravitational field, the quasi-geoid, and the national height reference surface. The study is based on deriving height anomaly values (quasi-geoid heights) for the benchmarks of a polygon from the national levelling network and their subsequent comparison with the theoretical values from the two investigated models. A key element for the reliability of the analysis is a set of 21 reference points determined through a precise GNSS methodology with a proven vertical accuracy of less than 20 mm [3], [4]. These high-precision data allow for an objective quality assessment of the transformation models and the identification of potential gross and systematic errors. The paper analyzes the discrepancies between the modelled and measured values, emphasizing that high-precision GNSS determinations are a mandatory requirement for the correct derivation and validation of local quasi-geoid models. The results provide insights into the applicability of the existing official software for solving high-precision engineering and scientific problems.
Publication details
References4
Instruction No. RD-02-20-1 of 15 January 2021 on the establishment and maintenance of the State Levelling Network, Ministry of Regional Development and Public Works, in Bulgaria;
Peneva E., On the implementation of the European Vertical Reference System in Bulgaria, 21th International Multidisciplinary Scientific Geo Conference Surveying, Geology and Mining, Ecology and Management (SGEM 2021). Conference proceedings. 2021. Albena, 14 - 22 August, 2021, ISSN 1314-2704, doi.org/DOI: 10.5593/sgem2021/2.1/s09.48
Tsanovski Yu.,GNSS Measurements for the Needs of Precise Height Determinations in Bulgaria , Annual of the University of Architecture, Civil Engineering and Geodesy-Sofia, issue 2, volume 54, 2021, ?. 211-217, ISSN 2534-9759
Tsanovski Yu, METHODOLOGY FOR ACCOUNTING DISPLACEMENTS OF THE OUTPUT COORDINATES FROM THE STATIC STATE GPS NETWORK IN GEODETIC PRACTICE, "ΕΎ23rd SGEM International Multidisciplinary Scientific GeoConference 2023, October 2023, DOI: 10.5593/sgem2023/2.1/s09.29, ISSN 1314-2704