Instruments used by Sailors: Directional Tools, Important Navigation Terms and Concepts

Imagine being on a ship in the middle of the ocean with water all around you. There are no directional signs, no landmarks and no roads. How will you decide which direction to go safely? For navigating safely in the ocean, there are some important directional instruments used by sailors. These instruments are helpful for sailing through the deep sea water while avoiding hidden dangers. Here are some of the important instruments used by sailors to navigate safely through the oceans along with related terms and concepts.

Table of Contents

• Compass
• Sextant
• Marine Radar
• GPS and Electronic Charts
• Echo Sounder

Compass

It is a reliable directional tool used by sailors for over 1,000 years. It has a magnetic needle that alights with earth’s magnetic field to always point towards north. Once the sailors know where north is, they can easily tell the rest of the three directions. Even in the darkest stormy night a sailor can steer the ship in the right direction using a compass. If the technology in ships fails for some reasons, compass remains a crucial source of information for sailors guiding them through the right direction in the water.

Sextant

A small triangular metal device that looks like the slice of a pizza has a mirror, a small telescope and a scale attached to the bottom edge. It computes the angle between horizon and sun or a star to help sailors understand their location on earth. By aligning the north star or sun through the sextant the sailors can detect the angle formed between horizon and celestial object to calculate the exact latitude on earth. 

Marine Radar

Short for radio detection and ranging(RADAR), it is one of the most important tools used by sailors to detect other objects such as icebergs, islands or ships sailing in the water to avoid collision. There is an antenna on the top of the ship that revolves around and sends radio or microwave electromagnetic waves. It detects the targets by reflected waves and generates a picture on a display of the ship about the surroundings. In modern ships these devices are used along with a GPS navigation system or sonar display to provide a combined view of the surroundings.

GPS and Electronic Charts

Global positioning system or GPS is fixed into the ship’s control room to monitor the map of the ocean with a red dot blinking to show the ship’s position and the direction it is heading to. This device on the ship is used by sailors to detect their location in the ocean. It receives signals from one of the GPS satellites orbiting earth. With the help of time each signal took to travel from space to the ship, the GPS system on the ship depicts the position of the ship on the map. 

Echo Sounder

An echo sounder is a device that sends out the sonar waves into water through a transmitter. The waves transmitted into the water, bounce back after hitting objects like rocks, fishes, ocean floor or wrecks of sunken ships. A receiver on the device listens to these waves and helps to detect any danger or obstacles beneath the water. The time it took for sound to echo back helps determine the distance of the dangerous objects from the ship. This instrument is extremely important for avoiding shipwrecks.

For many years, humans created tools that can help them navigate safely. From simple sticks that measured the angle of the sun to magnetic needles that always pointed north, we are still using these basic ideas as the foundation of modern technological tools and instruments used in the navigation by sailors. So, next time when you see a ship sailing in the ocean remember the names and functions of all the amazing instruments used by sailors.