Asking the Right Questions

David Patraiko, Director of Projects at The Nautical Institute, explores the distinction between data and information. He discusses which data sources should be checked and how to assess their reliability.

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Data and information, though often used interchangeably, have distinct meanings. Data generally refers to known, collected, and measured facts. On their own, these facts may not always provide significant insight. For instance, knowing the depth of water indicated on a chart may be of limited use. However, when this data is supplemented with information such as the state of the tide and the vessel's draft, it transforms into valuable information.

Information stems from data; however, the interpretation of that data or the algorithms used can either enhance its value or introduce errors that lead to misunderstandings.

If the underlying data is inaccurate, the subsequent information derived from it will also be unreliable. For example, incorrect speed inputs will produce unreliable vectors, as well as incorrect closest point of approach (CPA) and time to closest point of approach (TCPA) values. Even when data appears accurate, it may not represent the complete picture. Hydrographic measurements may suggest average depth between points, but fail to consider geological anomalies. This discrepancy may be attributed to the quality of the hydrographic survey performed.

A good navigator consistently seeks to verify the quality of their information and assesses the risks associated with decisions made based on this information.

Position

Global Navigation Satellite Systems (GNSS), such as GPS, serve as primary sources for position input in integrated navigation systems. When functioning correctly, they are remarkably accurate. However, this data can be susceptible to both intentional and unintentional jamming and spoofing, occurrences which have reportedly risen in frequency over the years. If multiple GNSS systems are available, validating GNSS inputs against an array of fitted systems (e.g., Glonass, Galileo, BeiDou) can effectively enhance accuracy. Bear in mind that non-GNSS inputs, such as visual bearings and radar depth contours, provide greater resilience due to their independence from satellite data. Practicing the use of these methods is crucial, not only for spotting errors but also to ensure confidence during satellite outages.

Radar

Radar is an exceptional tool for maintaining situational awareness for navigation and collision avoidance. While it operates independently of external inputs, skillful interpretation is required. Factors such as physical obstructions, weather conditions, sea state, and heavy traffic can influence radar images. Validating radar data through AIS, visual observations, and advice from VTS can help verify the integrity of the information obtained.

Depth/Under Keel Clearance

Under Keel Clearance (UKC) is critically important. Any lack of water impedes movement! Ensuring that UKC is accurate depends on numerous inputs. One must always question the accuracy of charted data, checking the date of the last survey and the category zone of confidence (CATZOC). This indicator reveals whether the data meets specific minimum standards, ranging from A1/six stars (highest reliability) to D/two stars (lowest reliability). Factors such as tide state and vessel squat also need to be considered. Echo sounder readings should be monitored visually, complemented by appropriate alarm settings. Visual cues, like changes in water color or breaking waves, can also alert navigators to imminent dangers.

Speed

Understanding speed is crucial, both over ground and through water. Speed over ground is best measured between various fixes, using multiple methods rather than relying solely on GNSS. Speed through water can be determined via a speed log or deduced from speed over ground with knowledge of set and drift.

Direction

Determining the direction of travel may seem straightforward, but it can be quite complex. One must consider heading (true/magnetic), and vector over ground or through water. Heading is essential for navigation and assessing a ship's aspect in regard to COLREGs application. It is crucial to verify the source of heading input: is it from GNSS or Gyro? If using GNSS, is it accurate? Have the gyros been checked? Checking heading against the chart's course is ineffective if both data sources are identical; utilizing leading marks serves as a more reliable method. For magnetic compasses, one must consider the last time it was calibrated.

Target Tracking

Accurately identifying targets is vital for any navigator. Primary tools for this process include visual observation, radar, AIS, and VTS, each possessing unique strengths and weaknesses. While visual assessment is excellent under favorable visibility, it can be hindered by weather conditions and optical illusions. Radar offers reliable data but can be susceptible to interference and misinterpretation. Lastly, AIS may provide inaccurate inputs (both manual and GNSS), and not all vessels or hazards carry AIS.

Passage Planning and Publications

When planning passages, ensure that publications are sourced from reputable suppliers and are current. Critical data can be sourced from agents, pilots, and VTS. Always cross-check weather routing advice with personal observations and experience. If uncertainty arises, consulting another source for guidance is advisable.

Optical

Human vision is a valuable source of data for situational awareness and decision-making. However, challenges exist—seeing is not always believing! Visibility issues, such as darkness or fog, can impair judgment. Bright bridges can compromise night vision, while shore lights may mislead navigators (for instance, is that red light a navigation mark or a building?). Visual observations should be corroborated with radar, charts, and identified objects in the passage plan. Binoculars can enhance visual capabilities, and emerging technologies such as cameras, low-light optics, and Augmented Reality (AR) may further improve this capability in the near future.

Think Twice

Safe navigation hinges on well-informed decisions that rely not merely on presented information but also on skills, experience, risk assessment, and intuition. Today’s mariners are inundated with a wealth of data and information— some of which is reliable, while others are not. Critical decisions necessitate careful consideration. Assess the trustworthiness of the information and its relevance to safety. What measures can you implement to mitigate risks? Involve the bridge team to leverage collective knowledge and experience. What contingency plans or abort points are in place? As we navigate an increasingly digital age, it is paramount that navigators understand the quality of the data and information they encounter, while also embracing the synergy between digital and analogue methodologies to uphold best practices in seamanship moving forward.

Marine Superintendent Sajith Babu AFNI Shares Insights on Maintaining Data Quality

How do you ensure that you are using data of the highest quality?
Cross-referencing data among multiple resources is vital for confirmation. Onboard a vessel, being aware of the errors and limitations of navigational equipment and operational procedures is crucial. It is essential to regularly compare GPS positions with radar fixes, visual fixes, echo sounder depths with chart soundings, and CPA/TCPA metrics across available radars even in uncongested waters. Regularly testing equipment is equally important; ensure operations align with the manufacturer’s instructions and company guidelines. Always regard data with suspicion for potential errors, and the best way to mitigate this risk is by properly maintaining equipment and systematically verifying the data received.

What experiences have you encountered with unreliable data at sea?
Although tools such as GPS, ECDIS, AIS, and ARPA have facilitated information accessibility for navigators, the prevalence of associated errors is rising. Reports of GPS signal loss, jamming, and spoofing have surged, particularly near the Suez Canal upon entering the Mediterranean Sea. The vessels we manage have noted that loss of GPS signals occurs frequently near Port Said, with one instance persisting for three days. Such disruptions are troublesome, especially when GPS signals are lost every five minutes. Alarms can distract the Officer of the Watch (OOW) and may inadvertently lead to accidents. Additionally, reports exist of GPS signal loss within the Persian Gulf and the challenges brought by insufficient quality data in ECDIS around the South China Sea. Overlapping ENC cells and the availability of small-scale charts in these areas can complicate matters. Personally, I make it a habit to keep paper charts for these regions accessible to the OOW, as not all vessels may have physical charts onboard.

Data should always be viewed with skepticism for errors, and maintaining equipment in good condition, along with checking or comparing all received data, is the best approach.

How can the maritime industry improve data quality collectively?
As the industry moves towards digitalized equipment, there is no reversing this trend. Improving data quality is an ongoing challenge. Proper use and awareness of each equipment’s limitations are essential for every OOW. A balanced perspective on the hazards of over-reliance on any single piece of equipment prompts navigators to compare data frequently for accuracy. Furthermore, we should encourage feedback from Masters and OOWs regarding significant navigational information, including suspected dangers and updates to navigational aids. Tools such as hydrographic notes or apps like H-Note can facilitate this process. As end-users of maritime equipment, we have a social responsibility to offer constructive feedback to enhance systems rather than merely criticize them.