Using and Testing a Search and Rescue Transponder (SART)

 

Your Guide to Seafaring

A Comprehensive Guide to Using and Testing a Search and Rescue Transponder (SART)

The Search and Rescue Transponder (SART) is a critical safety device used in maritime operations to locate ships and survival crafts during emergencies. This guide provides detailed instructions on how to use and test a SART to ensure it is operational and ready for use in distress situations.

Understanding the SART

A SART is a self-contained, battery-operated device that responds to radar signals from search and rescue (SAR) vessels or aircraft. It operates in the 9 GHz (X-band) radar frequency band and transmits a series of response signals, known as homing signals, which are displayed on the radar screen of the searching vessel.

Components of a SART

1. Transponder Unit: The main body of the SART, which contains the electronics and battery.
2. Antenna: The component that emits and receives radar signals.
3. Battery: Provides power to the SART, typically with a capacity to operate for 96 hours in standby mode and 8 hours in continuous transpond mode.
4. Mounting Bracket: Used to secure the SART on the vessel or in survival crafts.

How to Use a SART

1. Activation: Switch the SART to the "ON" position2. The visual indicator light and audible beeper should confirm that the device is operational.
2. Deployment: In an emergency, deploy the SART in a visible location, such as on the deck or in a survival craft. Ensure it is securely attached to prevent loss overboard.
3. Response to Radar Signals: When interrogated by a radar signal, the SART will transmit a series of homing signals. These signals appear on the radar screen of the searching vessel as a sequence of dots forming concentric circles.
4. Monitoring: Continuously monitor the radar display to ensure the SART is responding correctly and that the searching vessel can locate your position.

How to Test a SART

Regular testing of the SART is essential to ensure it is functional and ready for use in an emergency. Follow these steps for monthly and annual testing:

1. Visual Inspection: Check the casing for any cracks, punctures, or damage. Ensure the mounting bracket is secure and the device is not damaged.
2. Battery Check: Verify the battery expiration date and ensure it has sufficient power to cover the next routine voyage2. Replace the battery if it is near expiration or has expired.
3. Self-Test: Most SARTs have a self-test feature. Activate the self-test mode and check the visual indicator light and audible beeper. Ensure they are functioning correctly.
4. Radar Test: Perform a functional test using the ship's 9 GHz radar. Switch the SART to test mode, hold it in view of the radar antenna, and observe the radar display. The radar should show concentric circles indicating the SART is transmitting correctly.
5. Documentation: Record the test results and any maintenance performed on the SART. Ensure compliance with IMO standards and regulations.

Conclusion

The SART is a vital tool for maritime safety, providing a reliable means of locating vessels and survival crafts during emergencies. By following proper usage and testing procedures, mariners can ensure the SART is always ready for action, enhancing the chances of a successful rescue operation.

Automatic Identification System (AIS) Overview

 

Your Guide to Seafaring

The Automatic Identification System (AIS) is a vital maritime communication system designed to enhance navigational safety and efficiency. It allows ships to broadcast and receive information about other vessels, navigational aids, and shore-based facilities. This guide provides a comprehensive overview of AIS, its components, functionality, and applications.

Introduction

AIS was developed to improve maritime safety by providing real-time information about the positions, movements, and other relevant data of ships. It operates in the VHF maritime band and uses Self-Organizing Time Division Multiple Access (SOTDMA) technology to ensure reliable communication.

Historical Background

The International Maritime Organization (IMO) introduced AIS as part of the International Convention for the Safety of Life at Sea (SOLAS) in 2002. The system was designed to replace traditional methods of ship identification and tracking, such as visual sightings and radio communication.

Components of AIS

AIS consists of several key components:

Transceiver: The AIS transceiver is the core component that sends and receives AIS messages. It operates on two dedicated VHF channels: AIS 1 (161.975 MHz) for ship-to-ship communication and AIS 2 (162.025 MHz) for ship-to-shore communication.

GPS Receiver: The AIS system relies on a GPS receiver to obtain accurate position, course, and speed data of the vessel.

Display Unit: The AIS data is displayed on a screen, typically integrated with the ship's electronic chart display and information system (ECDIS) or radar.

Data Interface: The AIS system interfaces with other shipboard equipment, such as the gyrocompass, rate of turn indicator, and heading sensor, to gather additional navigational data.

Functionality of AIS

AIS operates by continuously broadcasting and receiving information about nearby vessels. Each AIS-equipped ship transmits data such as its unique identification, position, course, speed, and other relevant information. This data is received by other AIS-equipped ships and shore-based stations, allowing for real-time tracking and monitoring.

Types of AIS

There are two main types of AIS:

Class A: Required for all vessels over 300 gross tonnage (GT) and passenger ships. It provides full functionality, including dynamic data (position, course, speed) and static data (ship's name, type, dimensions).

Class B: Designed for smaller vessels and non-SOLAS ships. It offers limited functionality compared to Class A but still provides essential information for navigation and collision avoidance.

Applications of AIS

AIS has a wide range of applications in maritime operations:

Collision Avoidance: AIS helps mariners identify and track nearby vessels, reducing the risk of collisions.

Traffic Management: Vessel Traffic Services (VTS) use AIS to monitor and manage maritime traffic in busy waterways.

Search and Rescue: AIS data can be used to locate vessels in distress and coordinate rescue operations.

Port Operations: AIS assists in the efficient management of port traffic, allowing for better scheduling and docking of vessels.

Environmental Monitoring: AIS data can be used to monitor ship movements and detect potential environmental threats, such as oil spills.

Advantages of AIS

Enhanced Safety: By providing real-time information about nearby vessels, AIS significantly improves navigational safety.

Efficiency: AIS streamlines maritime operations by reducing the need for manual reporting and communication.

Transparency: AIS promotes transparency in maritime operations, allowing for better coordination and cooperation among vessels and authorities.

Conclusion

The Automatic Identification System (AIS) is a crucial tool for modern maritime navigation, offering real-time tracking and communication capabilities that enhance safety and efficiency. By understanding the components, functionality, and applications of AIS, mariners can better utilize this technology to navigate the seas safely and effectively.

 

Marine Radar Onboard Ships: An Overview

 

Marine Radar Onboard Ships: An Overview

Your Guide to Seafaring

Marine radar is an indispensable tool in modern maritime navigation, providing critical information that ensures the safety and efficiency of ships at sea. This comprehensive guide explores the intricacies of marine radar, its components, types, functions, and the technological advancements that have revolutionized its use.

Introduction

Marine radar is a vital navigational aid that helps detect and track objects such as other vessels, landmasses, buoys, and navigational hazards. It operates by emitting radio waves that reflect off objects, with the reflected signals processed to determine the object's distance, direction, speed, and course. This information is crucial for safe navigation, especially in poor visibility conditions such as fog, rain, or nighttime.

Historical Background

The development of radar technology dates back to the early 20th century, with significant advancements during World War II. Initially used for military applications, radar technology was adapted for maritime use to enhance navigation safety. The first marine radars were large and cumbersome, but technological advancements have made them more compact, efficient, and user-friendly.

Types of Marine Radar

Marine radar systems are broadly classified into two types based on the frequency bands they operate in: S-band radar and X-band radar.

• S-band Radar: Operating at a frequency of around 3 GHz, S-band radar is capable of penetrating rain, fog, and sea clutter more effectively. It offers longer-range detection and is ideal for tracking large targets such as ships and landmasses. S-band radar is particularly useful in adverse weather conditions.
• X-band Radar: Operating at a higher frequency of around 9 GHz, X-band radar provides higher resolution and sharper images. It is more sensitive to small targets like buoys and fishing boats. However, it can be more susceptible to weather conditions. X-band radar is commonly used for collision avoidance and navigation in congested waterways.

Main Components of Marine Radar

A typical marine radar system consists of three main components:

1. Antenna: The antenna emits radio waves and rotates continuously to cover a 360-degree area. It receives the reflected signals from objects in its path. There are two primary types of antennas used in marine radar:
• Open Array Antenna: Known for its higher gain and better performance, especially in distinguishing closely spaced targets.
• Radome Antenna: Enclosed in a protective dome, it is more compact and suited for smaller vessels.
2. Transmitter/Receiver Unit: This unit generates the radio waves emitted by the antenna and processes the returned signals. It calculates the range, bearing, speed, and course of detected targets.
3. Display Unit: The display unit shows the radar picture on a screen, which can be either a cathode ray tube (CRT) or a liquid crystal display (LCD). Modern radar systems often use high-resolution LCD screens for clearer images and enhanced user interaction.

Functions of Marine Radar

Marine radar performs several critical functions that enhance navigational safety and operational efficiency:

• Detection and Tracking: Marine radar identifies and tracks various objects, including other vessels, landmasses, buoys, and navigational hazards. This capability is vital for situational awareness.
• Navigation Aid: Radar provides essential information that aids in navigation through restricted visibility conditions. It helps mariners plot courses, identify safe passages, and avoid hazards.
• Collision Avoidance: One of the primary functions of marine radar is to prevent collisions at sea. Radar provides bearing and distance information about other vessels, enabling navigators to take evasive action when necessary.
• Automatic Radar Plotting Aid (ARPA): ARPA systems enhance radar functionality by automatically tracking the movement of multiple targets. ARPA calculates the closest point of approach (CPA) and the time to closest point of approach (TCPA), helping navigators assess collision risks and make informed decisions.
• Search and Rescue Operations: Marine radar is crucial in search and rescue missions, helping locate distressed vessels or individuals in the water.

Technological Advancements in Marine Radar

The marine radar industry has seen significant technological advancements, improving its functionality and usability:

• Solid-State Technology: Traditional magnetron-based radars are being replaced by solid-state radar technology, which offers better performance, reliability, and lower maintenance requirements.
• Broadband Radar: Broadband radar systems provide higher resolution and better target discrimination, especially at close ranges. They are particularly effective in detecting small targets and navigating in congested areas.
• Integration with Other Systems: Modern marine radar systems are often integrated with other navigational tools, such as Electronic Chart Display and Information Systems (ECDIS) and Automatic Identification Systems (AIS). This integration provides a comprehensive view of the navigational environment.
• User-Friendly Interfaces: Advances in user interface design have made marine radar systems more intuitive and easier to operate. Touchscreen displays, customizable interfaces, and advanced plotting features enhance the user experience.
• Environmental Adaptability: Modern radars can adjust their settings based on environmental conditions, optimizing performance in various weather and sea states.

Some of the main features of marine radar with ARPA integration are:

• Range scale: This is the maximum distance that the radar can cover. It can be adjusted by using the range key on the keyboard or by selecting from a menu on the screen. The range scale determines the size and resolution of the radar picture.
• Range rings: These are concentric circles that divide the radar screen into equal intervals. They help to measure the range of a target by counting the number of rings between the center of the display and the target echo.
• Variable range marker (VRM): This is a dashed circle that can be moved by using a scroll wheel or a trackball. It gives more accurate range measurements than range rings by touching the inner edge of the target echo.
• Electronic bearing line (EBL): This is a straight line that extends from the own ship’s position to any point on the screen. It gives more accurate bearing measurements than  compass rose by aligning with any target echo.
• Parallel index line (PI): This is a dashed line parallel to EBL that indicates how far off course or off-track own ship is from its intended course or track.
• Heading marker: This is an arrow at 0°T on top of EBL that shows own ship’s heading relative to true north.
• Course over ground (COG) vector: This is an arrow at own ship’s position that shows own ship’s course over ground relative to true north.
• Speed over ground (SOG) vector: This is an arrow at own ship’s position that shows own ship’s speed over ground relative to true north.
• True motion mode: This is a mode where own ship moves across the screen while targets remain stationary relative to true north.
• Relative motion mode: This is a mode where own ship remains stationary at the center of the screen while targets move across it relative to own ship.

Here are some tips on how to use marine radar effectively:

• Adjust gain control: Gain control adjusts the sensitivity of the radar receiver. It should be set so that background noise is just visible on screen without obscuring weak echoes from small targets or distant targets.
• Adjust sea clutter control: Sea clutter control reduces unwanted echoes from the sea surface caused by waves or swell. It should be set so that sea clutter does not interfere with target detection near the horizon or close range.
• Adjust rain clutter control: Rain clutter control reduces unwanted echoes from precipitation caused by rain or snow. It should be set so that rain clutter does not interfere with target detection in areas affected by weather conditions.
• Select appropriate range scale: Range scale should be selected depending on prevailing circumstances and conditions such as traffic density, proximity to the coastline, visibility etc. A longer range scale provides advance warning of approaching targets while shorter range scale provides better resolution for close-range targets.
• Use VRM and EBL for accurate measurements: VRM and EBL provide more accurate measurements than fixed range rings and compass rose for target’s range and bearing respectively. They also help to determine if there is a risk of collision by checking if the bearing remains constant with decreasing range.
• Use PI line for course keeping: PI line helps to keep own ship on its intended course or track by showing how far off it deviates from it due to wind, current etc. It also helps to estimate closest point of approach (CPA) with other vessels by showing how much clearance there will be between them at crossing situation.

 COMMON PROBLEMS ON MARINE RADAR

Marine radar is not without its challenges and limitations. Some of the problems that can affect the performance and accuracy of marine radar are:

• Clutter: Clutter refers to unwanted echoes or noise on the radar screen that can obscure or confuse the real targets. Clutter can be caused by various factors, such as rain, snow, fog, sea waves, birds, insects, interference from other radars or electronic devices, etc. To reduce clutter, the radar operator should adjust the gain control (sensitivity) so that only the relevant echoes are visible on the screen. The operator should also use filters or suppressors to eliminate specific types of clutter.
• Blind zones: Blind zones are areas where the radar cannot detect targets due to physical obstructions or limitations of the antenna. For example, blind zones can occur behind tall structures (such as masts or funnels), below or above the horizon (due to earth’s curvature), or close to own ship (due to minimum range). To avoid blind zones, the operator should use different range scales or switch between X-band (shorter wavelength) and S-band (longer wavelength) radars if available.
• False echoes: False echoes are misleading signals that appear on the radar screen but do not correspond to real targets. False echoes can be caused by various factors, such as reflection from land features (such as mountains or buildings), refraction from atmospheric layers (such as inversion or ducting), multipath propagation (when radio waves bounce off more than one surface), etc. To identify false echoes, the operator should compare them with visual observations or other sources of information (such as AIS or VHF).
• Shadow sectors: Shadow sectors are areas where a target is hidden from view by another target that is closer to own ship. For example, a small boat behind a large ship may not be visible on radar due to shadowing effect. To avoid shadow sectors, the operator should use different bearing lines or electronic bearing lines (EBLs) to measure the relative bearings of targets from own ship.
• Sea return: Sea return is a type of clutter that occurs when radio waves reflect off sea surface due to rough weather conditions or high wind speed. Sea return can mask small targets near own ship or create false targets at longer ranges. To reduce sea return, the operator should adjust sea clutter control (STC) which reduces sensitivity at short ranges.

 

Conclusion

Marine radar is an essential tool for maritime navigation, providing critical information that ensures the safety and efficiency of vessels at sea. From detecting and tracking objects to aiding in collision avoidance and search and rescue operations, marine radar plays a pivotal role in modern maritime operations. Technological advancements continue to enhance its capabilities, making it an indispensable asset for mariners worldwide.

Gyroscope

 

Your Guide to Seafaring

Earth is a example of gyroscope turning from east to west.

Here are your Keywords.

Gyroscopic Inertia – Maintain Orientation

Gyroscopic Precession – Change direction at right angle.

Phantom – support gyroscope.

Gyro Compass Error

Speed Error – Seek at setting position

Quadrantal Error – Swing from side to side.

Gimbaling Error – Tilt, Gimbals

A gyroscope is a device used for measuring or maintaining orientation and angular velocity. It operates based on the principles of angular momentum and has applications in navigation, stabilization, and various technologies. Here’s an in-depth look at gyroscopes, their types, functions, and applications.

Principle of Operation

The core principle behind a gyroscope is angular momentum. When a rotating object, such as a disk, is subjected to an external torque, it resists changes to its axis of rotation. This resistance allows the gyroscope to maintain its orientation.

Types of Gyroscopes

1. Mechanical Gyroscopes: The classic form, consisting of a spinning wheel or disk. These gyroscopes use the principles of angular momentum to maintain orientation.
2. Ring Laser Gyroscopes (RLGs): Utilize laser beams traveling in opposite directions in a circular path. The interference pattern of these beams provides information about the rate of rotation.
3. Fiber Optic Gyroscopes (FOGs): Similar to RLGs but use fiber optic cables to guide light. They are highly accurate and used in various high-precision applications.
4. MEMS Gyroscopes: Micro-Electro-Mechanical Systems gyroscopes are compact and widely used in consumer electronics like smartphones and drones. They use vibrating structures to measure angular velocity.

Applications of Gyroscopes

1. Navigation: Gyroscopes are integral to inertial navigation systems (INS) used in aircraft, ships, and spacecraft. They provide critical information about orientation and movement.
2. Stabilization: In cameras, ships, and drones, gyroscopes help stabilize the platform by detecting and compensating for unwanted motion.
3. Consumer Electronics: Smartphones, gaming controllers, and VR headsets use MEMS gyroscopes for orientation detection and motion tracking.
4. Aerospace and Defense: High-precision gyroscopes are used in missile guidance systems, aircraft navigation, and satellite orientation control.

Conclusion

Gyroscopes play a crucial role in modern technology, offering precise measurements and stabilization across various applications. From smartphones to spacecraft, these devices have revolutionized our ability to navigate, stabilize, and interact with the world around us. 

Moon Phase

Your Guide to Seafaring

The Moon exhibits different phases as the relative position of the Sun, Earth and Moon changes, appearing as a full moon when the Sun and Moon are on opposite sides of the Earth and as a new moon (dark moon) when they are on the same side. The phases of full moon and new moon are examples of syzygies, which occur when the Earth, Moon, and Sun lie (approximately) in a straight line. The time between two full moons (a Lunar month) is about 29.53 days (29 days, 12 hours, 44 minutes 2.8 seconds) on average (hence, the concept of the time frame of an approximated month was derived). This Synodic month is longer than the time it takes the Moon to make one orbit around the Earth with respect to the fixed stars (the Sidereal month), which is about 27.32 days (27 days, 7 hours, 43 minutes 11.5 seconds).This difference is caused by the fact that the Earth-Moon system is orbiting around the Sun at the same time the Moon is orbiting around the Earth.
^{The orbit of the moon  is very nearly circular (eccentricity 0.05) with a mean separation from the earth of about 384,000 km. which is about 60 earth radii. The plane of the orbit is tilted about 5 degrees with respect to the plane.}

Priming -  New Moon to 1st Quarter (1-3) / Full Moon to 3rd Quarter (5-7)
Lagging – 1st Quarter to Full Moon (3-5) / 3rd Quarter to New Moon (7-1)
Waxing Moon – The Moon between new and full when its visible part is increasing.
Waning Moon – The moon between full and new and when its visible part is decreasing.
Harvest Moon – The full moon nearest  the autumnal equinox.
Hunters Moon – The full moon one month after the autumnal equinox.
Neap Tides (1st Quarter or 3rd Quarter)
Spring Tides  (New Moon and Full Moon)

Position	Phase	Age (days)	Rise
1	New Moon	0	6 AM
2	1st Quarter	7 1/4	12 NN
3	Full Moon	14 1/2	18 PM
4	3rd Quarter	21 3/4	24 PM

Beaufort Wind Scale

Your Guide to Seafaring

The Beaufort Wind Scale is an empirical measure that relates wind speed to observed conditions at sea or on land1. Developed in 1805 by Sir Francis Beaufort, a British Royal Navy officer, the scale has been an essential tool for mariners, meteorologists, and various fields beyond since its inception2.

Historical Background

Sir Francis Beaufort devised the scale while serving on HMS Woolwich1. Initially, the scale was based on the effects of wind on a ship's sails, ranging from "just sufficient to give steerage" to "that which no canvas sails could withstand."1 Over time, the scale was refined and extended to include land observations, making it more versatile and widely applicable1.

Beaufort Number	Speed(kn)	Speed (mph)	Speed (km/h)	Description	Wave Height (meters)
0	0-1	0-1	0-1	Calm	Sea like a mirror
1	1-3	1-3	1-3	Light Air	Sea with ripples
2	4-6	4-7	4-6	Light Breeze	Small wavelets
3	7-10	8-12	7-10	Gentle Breeze	Large wavelets
4	11-16	13-18	11-16	Moderate Breeze	Small waves
5	17-21	19-24	17-21	Fresh Breeze	Moderate waves
6	22-27	25-31	22-27	Strong Breeze	Large waves
7	28-33	32-38	28-33	Near Gale	High waves
8	34-40	39-46	34-40	Gale	Very high waves
9	41-47	47-54	41-47	Severe Gale	High waves
10	48-55	55-63	48-55	Storm	Very high waves
11	56-63	64-72	56-63	Violent Storm	Exceptionally high waves
12	64+	73+	64+	Hurricane	Devastation

Modern Scale

The Beaufort Wind Scale is divided into 13 levels, ranging from 0 (calm) to 12 (hurricane force)1. Each level is associated with specific wind speeds, observed conditions, and probable wave heights3. Here's a detailed breakdown:

Functions and Applications

The Beaufort Wind Scale is widely used in maritime navigation, weather forecasting, and environmental monitoring1. It helps mariners assess wind conditions and make informed decisions to ensure safe navigation. Meteorologists use the scale to describe wind conditions in weather reports, and it is also used in various industries to assess the impact of wind on structures and activities.

Conclusion

The Beaufort Wind Scale remains a valuable tool for understanding and communicating wind conditions. Its simplicity and practicality have made it a staple in maritime and meteorological practices for over two centuries. By providing a standardized way to measure and describe wind speeds, the Beaufort Wind Scale continues to play a crucial role in ensuring safety and efficiency in various fields.