# The EGNOS Augmentation in Maritime Navigation +
## 1 Introduction
Similar systems are being developed by the US (Wide Area Augmentation System--WASS), Europe (European Geostationary Navigation Overlay Service--EGNOS), Japan (MTSAT Satellite based Augmentation System--MSAS), India (GAGAN), China (BD-SBAS) and Russia (System of Differential Correction and Monitoring). Thanks to these systems, the positioning characteristics of GNSS systems such as accuracy, reliability, continuity, availability and, especially, integrity can be considerably improved [8; 11]. EGNOS is the European SBAS, used for augmenting GPS and GLONAS. The purpose of the system is the transmission of differential corrections and information about failures of the GNSSs via satellites located in geostationary orbits as deeply detailed in chapter II. The maritime community is interested in EGNOS service tailored to the operational needs [12] in the European region, for improving accuracy and integrity information, especially where there is lack of infrastructure. However, even if more than 90% of maritime GNSS receiver models are SBAS compatible, only IMO MSC.401 and IEC 61108-4 (Shipborne DGPS and DGLONASS maritime radio-beacon receiver equipment) allow for the use of SBAS receiver in vessels, but there are no guidelines for their implementation. For this reason, European Commission (EC), European Space Agency (ESA) and the European Satellite Service Provider (ESSP) are working on common guidance for the manufactures for the implementation of SBAS in vessel receivers to be compliant with the operational requirements defined by the IMO. The aim of this work is to evaluate the performance of EGNOS augmentation in maritime navigation to mitigate the undesired effects obtained when GNSS navigation is conducted in \"hostile\" scenarios and, consequently, to provide an alternative method able to improve the accuracy of the navigation solution. In detail, corrections provided by the EGNOS Message Server (EMS) are applied in post processing using the open-source software RTKlib [13]. The assessment analysis was conducted on several data-collections carried out both in static and kinematic modes. Static data has involved 21 h of observations downloaded by a reference station belonging to EGNOS ground segment (RIMS). While a kinematic survey has been carried out onboard a small boat collectingraw data during different navigation phases such as the unberthing, cruise and turning. The boat was equipped with two low-cost GNSS receivers: the Ublov ZED F9P and the built-in smartphone chipset Broadcom BCM47755. The positioning solutions obtained by applying EGNOS corrections have been compared to positioning solutions computed using GPS-only Single Point Positioning (SPP), code-based differential positioning modes. Finally, the performances of all results have been evaluated by considering the PPK (Post Processing Kinematic) solution as ground truth. Hence, the performance analysis was conducted in terms of accuracy, availability and continuity, also verifying the satisfaction of IMO requirements. From the results, the accuracy improvements obtained thanks to the use of EGNOS corrections are evident, especially regarding the vertical component of the position. These results highlight the importance of using EGNOS to obtain accurate estimate of vertical component of the position that is a key parameter for the analysis of the sea conditions, which starts from the survey of the amplitudes of the vessel motions [14]. The paper is organized as follows: in Section 2 a description of EGNOS architecture is provided and its role in maritime sector is illustrated, while experimental setup is described in Section 3 and results are summarized in Chapter 4. Section 5 concludes the paper.