Navigating when GPS can’t be trusted

Why GNSS is easy to disrupt

GPS satellites orbit in medium Earth orbit at roughly 20,200 km.¹ By the time their signals reach a receiver they are extremely weak — below the background noise at the receiver input — and are recovered only through signal processing.² That makes them easy to overpower with a nearby transmitter (jamming) or to imitate with a counterfeit signal (spoofing).

The problem is now measurable at scale. IATA reports that GPS signal-loss events increased by 220% between 2021 and 2024,³ and that reports of interference rose 175% and GPS spoofing incidents 500% between 2023 and 2024.⁴ IATA's most recent risk assessment counts roughly 1.5 million instances of GPS signal loss across about 30.7 million flights from August 2021 to December 2025, with the rate per 1,000 flights rising from 28.1 in 2021 to 57.1 in 2025 (provisional), and notes that receiver recovery can in a significant number of cases exceed 30 minutes.⁵ European regulators describe interference as a regular occurrence, particularly on the edge of conflict zones.⁶

What “GPS-denied” means in practice

“GPS-denied” covers several different conditions, and they call for different defences:

• Loss of signal — jamming, terrain masking, indoor, underground or underwater operation. The receiver knows it has no fix.
• Degraded signal — intermittent reception or reduced accuracy, common in urban canyons and under interference.
• False signal — spoofing. The receiver may report a confident but wrong position, which is often more dangerous than no position at all.

The engineering question is rarely “what replaces GPS?” It is: how large can the position error grow during an outage of a given length, and how will the system know when a source is wrong?

The main alternatives at a glance

Each is examined in more depth, with its failure modes, in Alternatives to GPS compared.

Why diversity beats a single replacement

A US Department of Transportation evaluation of complementary PNT technologies found that only one vendor demonstrated performance in all applicable use-case scenarios, and concluded that the best strategy for resilient PNT is to pursue multiple technologies.¹⁰

In practice that means an inertial core aided by several independent sources, each with a different failure mode, and an integrity layer that can detect and exclude a source that has gone wrong. A passive source that does not rely on radio signals is valuable in that mix precisely because it fails differently.

How to evaluate an alternative for your platform

1. Define the requirement first. Outage duration, acceptable horizontal error over that time, and how quickly the system must detect a bad source.
2. Match the environment. Altitude band, terrain or sea state, lighting, weather, and whether the platform operates over areas with good reference data.
3. Check the data dependencies. Map- or database-matched methods are only as good as coverage, resolution and currency of that data.
4. Account for the platform. Magnetic and electrical interference, vibration, thermal range, mounting location and available power.
5. Ask how results were produced. Simulation, bench, captive-carry or flight? What baseline (for example, INS only)? What route, altitude, duration and dataset? Who ran it?
6. Plan integration early. Interfaces to the navigation filter, time synchronisation, integrity outputs and certification or qualification needs.

Limitations to keep in mind

• No single aid works everywhere. Every alternative has environments where it degrades.
• Map-matched methods inherit the limits of their maps; where reference data is sparse, performance drops.
• Published accuracy figures are conditional. A number without platform, altitude, map and duration is not comparable with another.
• Detecting spoofing and navigating without GNSS are related but separate capabilities.

Where Orbital Quantum fits

Orbital Quantum is a Canadian company developing True North Navigation™ quantum magnetometer modules for GPS-independent positioning. The approach reads the structure of Earth's magnetic field with a quantum magnetometer array and matches the live signature against a known field model to resolve position.

Read more on how True North Navigation works, or see Founder's Edition access on orbitalquantum.com.

Sources

1. GPS.gov — Space Segment — www.gps.gov
2. Safran Navigation & Timing — Measuring a GNSS signal and Gaussian noise power (2026) — safran-navigation-timing.com
3. IATA — EASA and IATA publish plan to mitigate GNSS interference risks (18 Jun 2025) — www.iata.org
4. IATA — 2024 Safety Report (26 Feb 2025) — www.iata.org
5. IATA — Safety Risk Assessment: GNSS Radio Frequency Interference, v6 (Feb 2026) — ic.iata.org
6. EASA — EASA and EUROCONTROL joint action plan on GNSS interference (26 Mar 2026) — www.easa.europa.eu
7. Groves, P. D. — Navigation using inertial sensors, IEEE AESS Magazine (2015) — discovery.ucl.ac.uk
8. Satellite Navigation (Springer) — review of GNSS-denied UAV navigation (2025) — link.springer.com
9. MDPI Engineering Proceedings — Celestial navigation in GNSS-denied environments (2025) — www.mdpi.com
10. US DOT / Volpe — Complementary PNT and GPS Backup Technologies Demonstration Report (Jan 2021) — www.transportation.gov
11. Gnadt et al. — Signal enhancement for magnetic navigation challenge problem (2020) — arxiv.org
12. Everitt et al. — quantum gravimetric maritime navigation trial, preprint (Aug 2026) — arxiv.org