AIR-MoPSy:
AIR-MoPSy – Atmospheric Impact on the R-Mode Positioning System
- Duration:
- 01.04.2025 - 31.03.2029
- Project coordinated by:
- Universität Greifswald
- Project manager (IOW):
- Dr. Volker Mohrholz
- Funding:
- Landesförderinstitut Mecklenburg-Vorpommern (LFI)
- Researcharea:
- Partners:
-
Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)
Satellite-based navigation systems (GNSS, Global Navigation Satellite System) provide essential services for positioning and time synchronization. They offer a wide range of technical applications, but also create dependencies. Natural or man-made interference with GNSS signals can have catastrophic consequences for air and sea traffic. In the current political situation in Europe, GNSS signals in the Baltic Sea are repeatedly subject to artificial interference. A backup system that provides sufficiently accurate position and time data in the event of GNSS interference is therefore of crucial importance. The DLR Institute of Communications and Navigation has been continuously developing such a system since 2017 with the terrestrial navigation system R-Mode (Ranging Mode). R-Mode is a cost-effective approach in which existing maritime radio stations transmit R-Mode signals in the medium wave range (300 kHz).
Each R-mode transmitter emits a ground wave and a air wave. The ground wave is used to determine the distance between the transmitter and receiver. The air wave is reflected in the E-layer of the atmosphere (90-130 km), whereby it is significantly attenuated during the day when it passes through the D-layer (60-90 km). At night, but also during fluctuations in the D-layer, this attenuation is eliminated or reduced. At the location of the R-mode receiver, the superposition of ground and air waves leads to a deterioration in R-mode accuracy depending on the state of the atmosphere. Due to insufficient scientific understanding and atmospheric variability, R-mode positioning at night and during the day in certain conditions of the D-layer does not yet meet the required accuracy of 10m for harbor approaches and 100m for coastal navigation.
The main objectives of this project are to a) better understand the physical processes behind the propagation of the air wave as a function of the atmospheric state, b) investigate and quantify the variability of all relevant physical parameters, and c) provide realistic error estimates for position determination with R-Mode. In addition, a warning system concept will be developed to inform R-Mode users about a limited accuracy of the R-Mode service and suggestions will be made to improve the R-Mode system based on the knowledge gained.
Each R-mode transmitter emits a ground wave and a air wave. The ground wave is used to determine the distance between the transmitter and receiver. The air wave is reflected in the E-layer of the atmosphere (90-130 km), whereby it is significantly attenuated during the day when it passes through the D-layer (60-90 km). At night, but also during fluctuations in the D-layer, this attenuation is eliminated or reduced. At the location of the R-mode receiver, the superposition of ground and air waves leads to a deterioration in R-mode accuracy depending on the state of the atmosphere. Due to insufficient scientific understanding and atmospheric variability, R-mode positioning at night and during the day in certain conditions of the D-layer does not yet meet the required accuracy of 10m for harbor approaches and 100m for coastal navigation.
The main objectives of this project are to a) better understand the physical processes behind the propagation of the air wave as a function of the atmospheric state, b) investigate and quantify the variability of all relevant physical parameters, and c) provide realistic error estimates for position determination with R-Mode. In addition, a warning system concept will be developed to inform R-Mode users about a limited accuracy of the R-Mode service and suggestions will be made to improve the R-Mode system based on the knowledge gained.