White Papers

June 18, 2020

Marine Navigation and the Development of the Motion Reference Unit

History of Marine Navigation

The Stars

Early sea-fairing explorers utilized the stars as their navigational aid.
Celestial navigation, also known as astronavigation, utilized devices such as the gnomon, Kamal, sea astrolabe, quadrant, cross-staff, back-staff, and sextant.

Magnetic Compass

Dating back as early as 200 BCE in China during the reign of the Qin dynasty, the Chinese originally used magnetism to construct fortune-telling boards, which were used for following directions in more than one way. Early magnetic compasses began to be commonly used as navigation aids in the 11th century.

Chronometer

Before the invention Chronometer in the 18th century, determining longitude with any amount of accuracy was nearly impossible (1). This device, which kept an accurate time, made it possible for voyagers to keep track of their geographical position with an accuracy that began to commercialize marine travel.

Gyroscope Compass

Max Schuler was responsible for the first seaworthy gyrocompass used for maritime navigation in 1908. Shortly following this release, an American gentleman named Elmer Sperry launched a similar product. It had a simpler manufacturing process, making it easily produced in large quantities (2). Sperry Marine, now owned by Northrup Grumman, went on to manufacture large quantities of gyrocompasses for many different commercial and military applications.

Radio and Radar

Early radio and radar navigation worked similarly to how RTK corrections are sent today. When a vessel was close enough to shore, the operator could receive data from a base station on land that sent corrections to the craft. RADAR, formally known as Radio Detection and Ranging Equipment, was first used by the Air Force in the 1940s during World War II (3).

LORAN

Building on the early radio-based navigation systems, LORAN, short for Long Range, operated on lower frequencies, which allowed data to be sent up to 1,500 miles (4).
Although the position accuracy at this distance was tens of miles, this was a tremendous improvement for marine ventures that required transatlantic navigation.

GPS-Positioning

Dating back to the mid-1960s, when the Space Race caused tensions between the Soviet Union and the United States, early GPS radio signals gave scientists the ability to calculate global positioning utilizing the “Doppler Effect”. The Doppler Effect was an analysis of the shift in radio signals that were received between a receiving host and the satellite. In the 1960s, submarines were used by the United States to carry nuclear missiles, and six satellites orbiting the globe (used to calculate orbital parameters) that could pinpoint a submarine’s position in a matter of minutes (5).

Navigation Equipment Today

Today’s marine navigation equipment must be robust, versatile, and built for long-term usage. The marine industry is exceptionally tight on time constraints, money, and manpower, so all components that go into voyages, testing, and navigation must minimize error at all costs. The navigation sensor solutions of the 21st century should offer end-user configurations for all application types.
A market analysis was conducted to identify the most critical navigation equipment and sensors for marine navigation, surveying, industrial ventures (drilling, cargo transfer, etc.), and research. An assortment of twenty randomly selected international standard documents, vessel manuals, and marine navigation studies were analyzed for their highlighted recommended equipment. The most discussed equipment and sensors can be seen in the plot below (6-25).

The top five most critical sensing components onboard any vessel are (in order of popularity) speed and distance logs, radar or sonar, gyro compasses, and magnetic compasses, and tied for fifth are GPS receivers and redundant tracking aids.
This shows that, regardless of your use case, many vital sources of useful information are available onboard at all times.
From this analysis, it is clear that the most useful system an end-user can benefit from is a sensor solution that can communicate with these components to receive and send useful data to accomplish many different tasks.

Current Market Solutions

The marine navigation industry is known for its price tag. Current market solutions for marine navigation and orientation compensation often push reliability and professionalism before product performance and functionality. But why?
An article titled “Why Does Marine Gear Cost So Much” sheds light on the main reasons behind sensor solutions in the marine navigation industry (26). Stainless steel costs much more than conventional steel, and bronze is much more expensive than brass. Small material changes to avoid degradation due to saltwater and humidity can add a larger price tag to any solution.
Many market solutions bring you consistency without looking for ways to improve and make more efficient solutions.

What Makes Inertial Labs Different

The Inertial Labs solution takes a different approach. By analyzing what sensors are available on marine vessels, Inertial Labs supplies end-users with many different variants of the Motion Reference Unit (MRU) product line such that they will only pay for what they will use.

Robust Kalman Filter

Additionally, the MRU product line has been engineered to accept aiding data from a multitude of different sensors. After years of research, the MRU product line has evolved to be configurable with the previously discussed top-five most critical commonly available sensing components on marine vessels.

The MRU Kalman filter gives users the ability to control the validity of aiding data or take our recommendations for configuring settings. Either way, the graphic below shows how the MRU takes in different sensor components and is able to produce a robust navigation and orientation solution for the marine industry.

Certificate of Calibration

Each unit supplied from the Inertial Labs facility comes factory calibrated within its operational temperature range. This means that regardless of the operating conditions, you can trust that the performance will be within the expected values. To affirm the end-user, the unit is then shipped with a Certificate of Calibration, which outlines the results and conditions for which the MRU was tested.

Long Recalibration Time

With an exceptionally long recalibration time of 6 years, the MRU dominates the market in terms of reliability and convenience.

Custom Output Data Formats

Inertial Labs allows each user to customize their own data packets inside the Graphic User Interface and select from commonly used formats used by Teledyne and Kongsberg products. This makes product replacement solutions easy and convenient. Additionally, for customers looking for large-volume replacement solutions, Inertial Labs commonly supplies custom interfaces and data formats for large-quantity orders.