engleski

Study on the Positioning Accuracy of GNSS/INS Systems Supported by DGPS and RTK Receivers for Hydrographic Surveys

Hydrographic surveys, in accordance with the International Hydrographic Organization (IHO) S-44 standard, can be carried out in five orders: Exclusive, Special, 1a, 1b and 2, for which mini- mum accuracy requirements for the applied positioning system have been set out. They are re- spectively: 1 m, 2 m, 5 m, 5 m and 20 m, with a confidence level of 95% in two-dimensional space. Global Navigation Satellite System (GNSS) network solutions (accuracy: 2–3 cm (p = 0.95)) and Differential Global Positioning System (DGPS) (accuracy: 1–2 m (p = 0.95)) are now com-monly used positioning methods in hydrography. Due to the fact that a new order of hydro-graphic surveys has appeared in the IHO S-44 standard from 2020— Exclusive, looking at the current positioning accuracy of the DGPS system, it is not known whether it can be used in it. The aim of this article is to determine the usefulness of GNSS/Inertial Navigation Systems (INS) for hydrographic surveys. During the research, it was used two INS: Ekinox2-U and Ellipse-D by the SBG Systems, which were supported by DGPS and Real Time Kinematic (RTK) receivers. GNSS/INS measurements were carried out during the manoeuvring of the Autono-mous/Unmanned Surface Vehicle (ASV/USV) named “HydroDron” on Kłodno lake in Zawory. The acquired data was processed using the mathematical model that allows to assess whether any positioning system at a given point in time meets (or not) the accuracy requirements for each IHO orders. The model was verified taking into account the historical and current test re- sults of DGPS and RTK systems. Tests have confirmed that the RTK system meets the require- ments of all IHO orders, even in situations where it is not 100% functioning properly. Moreover, it was proved that the DGPS system does not meet only the requirements provided for the most stringent IHO order, i.e., the Exclusive Order (horizontal position error ≤ 1 m (p = 0.95)). Statisti-cal analyses showed that it was only a few centimetres away to meet this criterion. Therefore, it can be expected that soon it will be used in all IHO orders.

positioning accuracy ; positioning availability ; Global Navigation Satellite System (GNSS) ; Iner-tial Navigation System (INS) ; Differential Global Positioning System (DGPS) ; Real Time Kine-matic (RTK) ; hydrographic surveys ; International Hydrographic Organization (IHO)

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