SIGMISDIGG Ensuring GNSS for military and safety-critical services in mountainous area

Satellite navigation plays a pivotal role not just in vehicles, mobile phones, banking transactions (especially those reliant on precise timing), and services provided by electricity and telecom companies, but also in critical domains like rescue operations and military endeavors, particularly concerning the modern infantry. Satellite navigation is a ubiquitous tool, albeit not universally accessible or accurate across all locations. Austria, given its unique topographical characteristics within the Alpine region, faces notable challenges in this regard. Notably, mountain valleys and ravines are among the areas where satellite navigation struggles, although this list is by no means exhaustive when discussing natural topography. Moreover, the presence of urban canyons and narrow city streets compounds the issue, making reception of signals from global satellite navigation systems (GNSS), especially given the current equipment used by the Austrian Armed Forces (which primarily employs single-frequency receivers, specifically GPS L1-only models), incredibly challenging or even impossible.

Potential solutions do exist to mitigate these navigational challenges. One viable option is the adoption of multi-GNSS receivers. However, this avenue demands substantial investments. A precise multi-GNSS receiver without any specialized features comes with a price tag of at least €10,000, not to mention the additional costs associated with acquiring compatible antennas, reference stations for Differential GNSS (DGNSS), and Multi-GNSS software. With just 100 users, the cumulative expenditure surpasses €1.5 million. The efficacy of multi-GNSS receivers in providing an absolute solution remains an open question, as they may still contend with issues such as multipath effects and unfavorable satellite configurations. Furthermore, procurement timelines within the military sector are significantly longer (exceeding 15 years) compared to the civilian world (which typically operates on approximately 3-year cycles).

Are there alternative means of navigation in narrow valleys or urban canyons when users are restricted to GNSS receivers that can only track a single global satellite navigation system (e.g., GPS or Galileo)? This feasibility study aimed to unravel answers to this pressing question.

To achieve this objective, three distinct approaches were explored:

1. GNSS Re-Radiator / Repeater
2. Local Mobile Pseudolite Systems
3. GNSS Reflectometry in Valleys

The ultimate goal and anticipated outcome of this study were to provide a recommendation for achieving technically sound and cost-effective GPS positioning and navigation capabilities within the Austrian Alps, specifically tailored to the needs of the Austrian Armed Forces, all without the necessity of procuring new multi-GNSS receivers. Such an achievement would yield significant cost savings in comparison to a full-scale equipment replacement.