To counter these risks, the German Aerospace Center (DLR), together with research bodies, government agencies, and private-sector partners, has created an alternative to satellite-based positioning. Known as Ranging Mode (R-Mode), this terrestrial radio navigation solution is now entering the standardisation phase. Plans are underway to expand the testing area in 2025 to include territories in Finland and Estonia.
Between 2017 and 2021, DLR led the development of the world's first large-scale testing ground for R-Mode, laying the groundwork for a backup system across the Baltic. "This first step towards establishing a maritime backup system in the Baltic Sea region has demonstrated that R-Mode technology works in practice as an alternative terrestrial navigation system, enabling ship positioning even without satellite-based systems," said Anke Kaysser-Pyzalla, Chair of the DLR Executive Board. "With this, DLR is not only making an important contribution to maritime safety, but ultimately also supporting economic performance."
R-Mode provides an economical alternative by utilizing existing radio infrastructure from national maritime authorities. It operates on both medium-wave and very high-frequency radio bands, making use of shore-based transmitters to support navigation when satellite signals are compromised. Over the past seven years, eight R-Mode transmitters have been deployed along an 800-kilometer corridor from Heligoland to Stockholm.
This testbed is now being shared among researchers, regulatory agencies, and companies for further trials. The goal is to refine receiver technologies and enable real-world applications using R-Mode data.
The effort gained momentum in 2023 with the launch of the ORMOBASS project, which aims to broaden the test zone to encompass the maritime corridor between Sweden, Finland, and Estonia. After assessing the region's existing radio beacon infrastructure in 2024, project members drafted an expansion strategy. Implementation is scheduled for 2025 and 2026, during which all core R-Mode functions across both radio frequency bands will be finalised and handed over to maritime authorities for operational use.
DLR is overseeing the overall project coordination while also leading technical efforts in system architecture, receiver development, field testing, and standardisation processes.
Uniformity is key for real-world deployment. Vessels navigating international waters require consistent R-Mode signals and certified on-board receivers. These criteria depend on international standardisation. The ORMOBASS concept for the medium-wave R-Mode signal has been integrated into IALA Guideline 1187, which outlines signal features and messaging protocols. This milestone is the result of a five-year collaboration, incorporating expertise from prior Baltic projects as well as insights from Canadian and South Korean deployments.
Guideline 1187, published in early 2025 by the International Organisation for Marine Aids to Navigation (IALA), is now publicly accessible. Implementation of the standardised medium-wave signal is underway in the Baltic and is set to be available between Germany, Finland and Estonia from early 2026.
Related Links
DLR Institute of Communications and Navigation
GPS Applications, Technology and Suppliers
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