Multipath: A Challenge for Position Reference Systems

Multipath refers to a phenomenon where signals from position reference systems, such as GPS or USBL (Ultra-Short Baseline) acoustics, are deflected or reflected by nearby structures or surfaces. This results in the receiver interpreting multiple signal paths, leading to errors in position determination. Multipath effects are a significant concern in Dynamic Positioning (DP) operations, where precision is critical.

How Multipath Occurs

1. Signal Reflection: Signals bounce off obstacles such as vessel structures, offshore platforms, or the seabed.
2. Delayed Arrival: Reflected signals take longer to reach the receiver compared to direct signals, introducing positional inaccuracies.
3. Misinterpretation: The system cannot distinguish between direct and reflected signals, causing errors in calculations.

Systems Affected by Multipath

1. GPS/DGPS: Signal reflections from nearby structures or water surfaces lead to inaccuracies in satellite-based positioning systems.
2. USBL Acoustics: Acoustic signals reflected by subsea structures or the seabed affect underwater positioning systems.
3. Laser and Radar Systems: Reflections from shiny or angular surfaces can distort data interpretation.

Impact of Multipath on DP Operations

• Reduced Accuracy: Errors in positional data compromise station-keeping and heading stability.
• Increased Drift Risk: Uncorrected multipath effects can cause the vessel to deviate from its intended position.
• Operational Challenges: Misleading data complicates tasks like subsea construction, ROV operations, or cable laying.

Mitigation Strategies

1. Antenna/Transducer Placement: Position sensors in locations less prone to reflections, such as elevated or unobstructed areas.
2. Signal Filtering: Use advanced algorithms, like the Kalman Filter, to identify and mitigate multipath errors.
3. Redundant Systems: Combine data from multiple position reference systems to cross-check and validate accuracy.
4. Environmental Awareness: Minimize operations near reflective structures or surfaces whenever possible.

Lerus Training: Navigating Signal Challenges in Offshore Operations

At Lerus Training, we offer comprehensive courses on handling Multipath effects in Dynamic Positioning (DP) operations. Our training programs include:

• Understanding the causes and impacts of multipath on positioning systems.
• Practical strategies for mitigating multipath errors using advanced equipment and techniques.
• Simulated scenarios to enhance decision-making skills during multipath-related challenges.

With expert instructors and state-of-the-art facilities, Lerus Training ensures participants are equipped to address and overcome signal-related challenges in real-world offshore environments.