Heading Accuracy by Dual Antenna GNSS using Differential and Real Time Kinematic Techniques Compared to Gyrocompass

Abstract

Vessel heading is the direction in which ships are moving at any specific moment. Vessel heading is crucial for navigation as it helps in determining the vessel's course, making steering decisions, and ensuring the vessel follows a desired path. In maritime history, heading has always been a myth that needs to be figured out by all sailors at all time. In ancient times, celestial bodies were used to acquire destinations referred to true north. The accuracy of vessel heading is essential for safe and precise navigation, especially in challenging maritime conditions. Vessel heading instruments, have undergone evolution starting from lodestones as the earliest natural magnetic compass to modern-day gyrocompasses, laser gyros, and inertial systems. With the advent of satellite technology and global navigation satellite systems (GNSS) on board vessels, there has been a paradigm shift in calculating courses over ground, driven by the limitations and errors associated with magnetic compasses, such as variation and deviation in addition to the high costs of gyrocompasses. In response to the challenges posed by the drawbacks, this paper delves into two alternative techniques and systems for acquiring vessels' true heading. The first method employs real-time kinematics (RTK) with dual antennas, while the second utilizes a differential global positioning system (DGPS) with dual antennas also. This paper aims to check if these novel techniques are accounted for, to provide a reliable alternative to traditional heading acquisition from compasses. To assess the effectiveness of these new techniques, a correlation analysis was conducted comparing headings obtained from the gyrocompass with the heading from both RTK and DGPS, in both static and dynamic modes. The results revealed a remarkably strong correlation of 0.9 between the gyrocompass and both RTK and DGPS receivers, with a negligible standard deviation of ±0.1° in static and ±0.18° in dynamic. This comparative study underscores the potential of the proposed GNSS-based methods as accurate and cost-effective alternatives for acquiring vessel headings, showcasing their reliability in both static and dynamic conditions. The comparison of different heading acquisition techniques is important in determining which method provides the most accurate and reliable results in different conditions. This involves implementing redundant or complementary methods to ensure reliability in critical applications.