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Advanced Receiver Autonomous Integrity Monitoring for applicaTions beyOnd aviatiOn sector - ARAIMTOO


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The ARAIMTOO project analyzed and validated the extension of Advanced RAIM to user sectors beyond the aviation ones. For maritime, UASs and rail sectors the project identified the operations whose user requirements are fulfilled by current Aviation ARAIM concept. In addition, an evolution of ARAIM in each of those sectors was developed to satisfy a wider range of operations.

Contract Number: Call for TendersNo DEFIS/2020/OP/0009

Project Segment: Horizon 2020

Duration: 16 months (July 2021 – October 2022)

Budget: €300 000

Project Partners: GMV (Spain), NLR (The Netherlands), VVA (Italy)

Project Coordinator:

Javier Fidalgo Prieto (GMV)


European Commission Project Manager:

Ilaria Martini (EC-JRC)


Juan Pablo Boyero (EC-DEFIS)


The Advanced Receiver Autonomous Integrity Monitoring (ARAIM) is an evolution of the Receiver Autonomous Integrity Monitoring (RAIM) integrity technique recently developed to protect multi-constellation users by means of robust user algorithms. ARAIM includes an offline ground monitoring architecture, which provides updates on the nominal performance and fault rates of multiple constellations. This integrity data is contained in the Integrity Support Message (ISM) that is generated by an offline ground monitoring network and is provided to the airborne fleet through the GNSS signals.

The original ARAIM concept has been developed to serve the Aviation sector but it can be extended to other sectors which have similar and even more demanding requirements than aviation users for safety critical operations. Rail, Maritime, Road, Unmanned Aerial Vehicles (UAVs), Location Based Services (LBS) and Space User Sectors were analysed as potential target sectors in the project.


Project objectives

The European Commission launched the project with the following objectives:

  • Identification of non-aviation applications within different User Sectors, including Rail, Maritime, Road, LBS, UAVs and Space, with need of GNSS integrity capability and identification of their user needs in terms of GNSS Key Performance Indicators. Description of the standardisation landscape of non-aviation applications, definition of integrity technical parameters.
  • Identification of competing technologies with ARAIM, identification of added value of ARAIM and possible combinations with other innovative Position Navigation and Time (PNT) concepts. Prioritization of most promising applications for ARAIM penetration taking into account different criteria as user equipment cost, benefits expected, a-priori feasibility to comply with the requirements, relevance of the applications, etc.
  • Gap analysis to identify areas of improvement of ARAIM for the adaptation of this concept to non-aviation applications, covering Fault Tree Analysis, ARAIM user algorithm, ISM parameters and values, user error model, etc.
  • Definition of ARAIM evolutions, this is, modifications to the original ARAIM algorithm to cover the identified gaps in order to adapt ARAIM concept to non-aviation users for a set of selected sectors.
  • Proof-Of-Concept of the proposed ARAIM evolutions by a dedicated experimentation using SW implementations with the goal to analyse whether the non-aviation user requirements are met with the current ARAIM solution from aviation sector and with the proposed ARAIM evolutions.



Six non-aviation user sectors have been considered for the penetration of ARAIM concept, namely: Rail, Road, Maritime, UAVs, LBS and Space. The user requirements of the different applications in each of those sectors have been investigated based on literature review including GNSS standards and EUSPA User Consultation Platform Reports and based on interviews with relevant experts. The goal was to quantify the user requirements to assess the compliance of such non-aviation requirements by the performances achievable with the evolutions of the ARAIM concept.

Among all the sectors considered, the three most promising User Sectors for ARAIM evolutions - Rail, Maritime and UAVs - were retained in the project to develop corresponding solutions. The following high-level ARAIM evolutions have been investigated:

  • For Rail User sector, the combination of Space Based Augmentation System (SBAS) with ARAIM, providing safety barriers against local effects plus hybridization with Inertial Measurement Unit (IMU) and/or Odometer could allow to cope with the harsh environments and stringent integrity requirements typical of Rail Safety Of Life (SoL) applications.


Figure 1 - High-level architecture of ARAIM Evolution for Rail



Figure 2 - Receiver Architecture for the ARAIM Evolution for Rail


The Hybridization of GNSS with IMU has been extensively studied in ARAIMTOO and relies on the following principles:

  • Propagation of ARAIM Solution:
    • Propagate the ARAIM solution with the inertial sensors (or any other relative positioning sensor),
    • The Protection Levels (PLs) would be degraded according to a safe bounding that depend on the sensor quality,
    • The propagated solution can be used to cope with the lack of satellites in view when the propagated solution is better than the current one,
  • Improvement of FDE:
    • An FDE based on a filter hybridizing GNSS and other sensors provides improved performances, especially in harsh environments,
  • Measurements from previous epochs:
    • In harsh environments phase-smoothing is not possible. Doppler-smoothing can be used instead,
    • Smoothing could be aided by IMU/Odometer and a clock with good short-term stability,
  • Improvement of measurement error monitoring
    • Environmental conditions change due to local effects, so they need to be monitored,
    • Hybridization can help to better monitor the level of error in the measurements.


  • For Maritime User Sector an ARAIM solution based on multiple antenna processing in combination with SBAS is investigated.

The following figure depicts the high-level architecture for the proposed ARAIM Evolution for Maritime.



Figure 3 - High-level architecture of ARAIM Evolution for Maritime


The Receiver Architecture is depicted in the following figure.



Figure 4 - Receiver Architecture for the ARAIM Evolution for Maritime


  • For UAVs User Sector, the combination of Precise Point Positioning (PPP) techniques with an integrity algorithm at user level as ARAIM plus the hybridization with IMU could allow to cope with harsh environments typical of urban areas and the stringent accuracy and integrity requirements of UAVs in urban environments.



Figure 5 - High-level architecture of ARAIM Evolution for UAVs


The Receiver Architecture is depicted in the following figure.


Figure 6 - Receiver Architecture for the ARAIM Evolution for UAVs



The project has shown by means of simulation and real data experimentation that current ARAIM concept can already satisfy operations in the sectors retained.

In addition, the evolution developed for each sector has been shown able to extend the list of operations that can be satisfied.

The Table below collects the operations satisfied per sector.




ARAIM for Aviation

ARAIM Evolution for Maritime, UAS and Rail


-General Navigation: Ocean

-Autonomous Vessels: Ocean navigation

-Autonomous Vessels: Ocean Navigation

-General Navigation: Ocean, Coastal, Port Approach, Inland Waterways

-General Navigation (SOLAS); Inland waterways


-Station-keeping / anchor-watch alarms. DP systems         


-Open sky Operations            

-Open sky Operations

-Drone Operations under U-Space

-Operations in proximity of critical infrastructures

-Search & Rescue applications



-Fleet Management (in open sky)

-Cargo Monitoring (in open sky)

-Energy Charging (in open sky)

-Level Crossing Protection,

-Train integrity and train length monitoring,

-Door control supervision,

-Trackside personnel protection,

-Management of emergencies,

-Location of GSM Reports,

-Fleet Management,

-Cargo Monitoring,

-Energy charging,

-Infrastructure charging,

-Hazardous cargo monitoring,          

-Virtual Balise



The ARAIM concept, architecture and user algorithm which serve aviation users, can satisfy maritime, UAVs and Rail communities by providing the robustness required by safety critical operations. The need to cope with local errors was addressed with the ARAIM evolution developed and validated in the project which showed that the range of operations satisfied can be increased and the penetration of ARAIM facilitated.

The contribution of the project to the standardization activities to foster the adoption of ARAIM in combinations with other technologies was provided through the presentation of the project in the relevant working groups.

ARAIMTOO final report is available.

ARAIMTOO: Advanced Receiver Autonomous Integrity Monitoring for applicaTions beyOnd aviatiOn sector
(1.95 MB - PDF)

Disclaimer: The project results represent the views of the consortium. They do not necessarily represent the views of the European Commission and they do not commit the Commission to implementing the results.