EGNOS contribution to INFOMAR surveys

Tuesday, February 23, 2021

INFOMAR is Ireland's national marine mapping programme, a funded joint programme by the Department of the Environment, Climate and Communication between the Geological Survey Ireland and the Marine Institute, whose objective is to map the physical, chemical and biological features of Ireland’s seabed.

INFOMAR surveys primarily collect bathymetry data, using multibeam echosounders. The surveys are performed as part of an ongoing (>20 years) effort to map Ireland's seabed and are currently set to continue until 2026. Surveys are conducted throughout the year, with the highest level of effort during summer, when weather conditions are most favourable. They also collect 'backscatter' information from these instruments enabling them to infer the encountered seabed types. Additionally, several of the used vessels are fitted with Sub-bottom Profilers, geophysical instruments which provide information on the sub-seafloor composition and structure. Where required, seabed samples and other measurements are taken.

EGNOS has been utilised on INFOMAR’s vessels since 2011, when receiving hardware capable of decoding the signals. According to David Hardy, Geologist at Geological Survey Ireland, “EGNOS has replaced beacon DGPS sources and reduced the number and range of equipment required on our vessels; therefore it reduced system complexity and potential points of failure” . The surveys are intended to provide a modern high-quality baseline dataset. The data are then post-processed and become available to a wide range of users; who use it for hydrographic products, environmental studies, fisheries, renewables, petroleum exploration, marine tourism, aquaculture, regulatory & educational purposes. All data is available free of charge and can be commonly accessed through their website.

All inshore vessels operated by the Geological Survey of Ireland use EGNOS to support real-time navigation within Irish waters, up to 30nm from shore. The EGNOS corrections are received, decoded and applied to improve positional accuracy, significantly beyond standalone GNSS. Following the acquisition, additional post-processing is performed to further improve the navigation solution but this is primarily driven by their need to use the Inertial Navigation System (INS) height readings to correct the tidal effects (requiring an accuracy of <10cm).

Vessel positioning is achieved with Applanix POS MV systems, which utilise Trimble GNSS receivers with an integrated ability to decode and use EGNOS signals. Stand-alone terrestrial GNSS systems from Leica and Trimble are used to support operations.

Mr. Hardy emphasizes the advantages of EGNOS since “it is of significant value to our work and of very clear benefit to us. The improved positional quality it provides (beyond bare GNSS) supports the efficiency and safety of our operations. The increased positional certainty allows us to improve our line-keeping and sonar coverage efficiency throughout operations. The improved positioning accuracy also allows us to operate in areas of critical depths with confidence” .