Advancing navigation technology has secured shipping’s foundational role in modern supply chains. Yet maritime navigation is not a solved problem. Beyond the effects of the sea’s unique environment, ship owners and operators face modern challenges, such as the growing incidence of GNSS jamming and spoofing. This article will explore the role simulation can play when evaluating maritime GNSS/INS solutions.
Test maritime navigation scenarios anywhere on Earth
Taking GNSS and INS systems out to sea can yield valuable insights into the hardware’s shipboard performance. However, time and budgets will always constrain those insights to specific ships, sea states, and weather conditions. A comprehensive testing regime would be prohibitively expensive.
That’s where GNSS/INS simulation comes into its own.
Consider the impact of antenna and navigation system placement. Unlike the short distances in an aircraft or ground vehicle, the separation between a ship’s GNSS antennas and its Inertial Measurement Unit (IMU) is often tens of meters along the ship’s x, y, and z axes. The resulting lever arm can affect the accuracy of a navigation system’s positioning and attitude data — especially under dynamic conditions at sea.
Advanced GNSS/INS simulators let you configure test scenarios for different vessel types, maritime environments, and environmental conditions.
- Configure simulations with distinct x, y, and z lever arms to model system performance with full 6-DOF motion.
- Place the simulated vessel anywhere on Earth while setting GNSS satellite visibility and performance levels.
- Introduce multipath reflections and other environmental impacts on GNSS signal quality.
- Observe system performance under complex sea states by setting six independent distance and angular limits with six distinct time periods.
Without leaving the lab, you can evaluate systems installed on tugboats on Lake Michigan, bulk carriers entering the Yangtze Delta, or warships cruising the Indian Ocean.
Simulating GNSS interference at sea
Traditionally, natural and industrial radio-frequency sources were the only forms of interference that concerned commercial operators and their navigation system vendors. Adversarial interference was a navy’s concern. That is no longer the case. A steady rise in malicious interference — jamming and spoofing — has impacted shipping worldwide.
With jamming, a bad actor generates a radio-frequency signal on the same frequencies used by GNSS satellites. The false signal is so powerful that receivers lose their lock on the true GNSS signals.
Spoofing takes a more refined approach by broadcasting a signal similar to those from GNSS satellites. Receivers lock onto the false signal and report inaccurate positions. Vessels could veer off course if spoofing goes undetected, posing significant risks to the crew, the ship, and the environment.
We discussed jamming and spoofing in several articles last year, but the situation continues to worsen. In early 2026, the Royal Institute of Navigation issued a report describing the many GNSS-dependent systems impacted by this interference. One month later, the European nations bordering the North and Baltic Seas published an open letter highlighting the maritime risks from jamming and spoofing. Hostilities in the Persian Gulf, the ongoing invasion of Ukraine, and emerging GNSS interference hubs in the South China Sea are impacting the world’s busiest shipping routes. New hostilities in the Persian Gulf include multiple jamming and spoofing events every day.
GNSS/INS simulation can help mitigate the interference risks by refining technical solutions and operational procedures.
Precise, repeatable CAST Navigation GNSS/INS simulations
Since the arrival of GPS more than four decades ago, CAST Navigation has supplied GNSS simulation solutions to military and commercial customers for testing GNSS, inertial, and antenna systems. Our solutions can help operators and navigation system providers develop comprehensive test programs that reproduce the complexity of contemporary maritime operations.
CAST solutions are known for providing precise, repeatable results with best-in-class coherence between GNSS and INS simulator outputs. We take a flexible approach to our platform design, allowing customers to configure the simulation capabilities they need today while providing a path for future growth. A CAST Navigation solution may contain one or more of the following capabilities:
GNSS: Simulate RF signals from modernized GPS and other positioning constellations and send precise, repeatable test signals (legitimate or spoofed) to stimulate navigation devices.
Jamming: Emulate multipath urban interference and adversarial jamming with control over multiple interference parameters and send distinct interference signals to up to seven antenna output elements.
Inertial: Provide high-rate, high-fidelity inertial data to complex EGI and GNSS/INS systems by configuring IMU sensor block output performance characteristics and drift rates.
CRPA: Generate a complete set of coherent, accurate, and fully programmable RF signals to test phased array or multi-element antenna systems.
CAST Navigation’s customers can use our solutions to run high-fidelity simulations that recreate the unique conditions of maritime operations as well as the emerging threats from jamming and spoofing — all without leaving the laboratory.
Contact CAST Navigation today to learn more about using GNSS/INS simulation to improve maritime navigation.
