fig congress 2018 - Refraction coefficient determination and modelling for the territory of the Kingdom Of Saudi Arabia
Othman Al-Kherayef, Vasil Valchinov, Rossen Grebenitcharsky, Stanislava Valcheva, Bandar Al-Muslmani
The current paper presents the results from the Refraction Coefficient Determination for Precise Levelling Observation (RCD_PLO) project in relation to the establishment of a new National Vertical Reference Frame for the Kingdom of Saudi Arabia. A specialised software for processing more than 1 200 000 records of precise levelling measurements and temperature observation data was developed and used for refraction coefficient modelling. The modelling was based on the Kukkamaki’s classical formula and a newly derived formula for the refraction coefficient, taking into account the topography roughness along the line of sight by employing the so-called ‘equivalent heights’. The results were subjected to statistical and correlation analyses and later validated using levelling line and loop misclosures. 2D and 3D (GIS-based) models of refraction coefficient were also build. At the end of the paper, recommendations for the usage of the derived refraction coefficient models are given, considering the required levelling accuracy, height levels, type of the atmosphere (normal or inverse) and availability of temperature measurements.
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