How is ocean navigation done

This is what's in our cars, sailboats, phones and so on. It also can't tell you which direction you're pointing towards. So you can't use it to measure bearings. GPS is an American technology, and China, Russia, and Europe have their own variants, although they are not as widely supported. Nowadays, you can get a reliable, easy-to-use chartplotter , made by a reputable brand, with all the functionalities of an advanced marine GPS, at a fraction of the price.

Click here to read my recommendation. An echo sounder is a sonar that's used to determine the water depth. It uses sound waves and measures the delay of the reflections.

This tells the distance to the bottom. Echo sounding can be used to estimate a location but it's not very accurate. You also need some sort of bearing. Then check the chart and your current depth. Check at what point your depth and the bearing intersect. You can use sounding by itself to estimate a location, but it's a bit tedious. You literally measure a lot of points and draw up your own depth chart. Then compare it to an existing chart to estimate your location.

If you're sailing in a port or bay, there are lots of other vessels and objects to avoid. So you want to stay on course accurately. To do this, you need to monitor your position very carefully. If you want to avoid to have to plot your position every minute, you could use parallel indexing to stay on course.

Parallel indexing is simple. Take a fixed object. Through it, draw a line that's parallel to your course. Then monitor the echo of the object on the radar. As long as it stays glued to the line, you're on course. You can also measure the distance from your old position. For this, you need your course and speed. This is called dead reckoning.

It's the same principle. Your old position is the 'object'. Your course is the angle bearing , and your speed is the distance, giving you a line of position. This method isn't used a lot, but it can be handy. We check when the top of the lighthouse appears on the horizon. If we know the height of the lighthouse, and our eye height, you can calculate how far away we are.

Using some algebra, involving the curvature of the Earth. Most navigational almanacs including Reeds Nautical Almanac - Rising and Dipping distances contain some sort of a table that gives you the distance. If you have the distance, that's a line of position. Then just point your compass at it for the bearing, and you have your fix. What did early explorers use to navigate? The most common tools for ancient navigators were:.

The astrolabe is an ancient navigation instrument that measures the inclined position of stars or planets. It can be used during day and night. It was used during the Middle Ages and literally means 'the one that catches the heavenly bodies'. The back staff measures the altitude of the sun using its shadow. It was invented in the 16th century.

Before that, navigators had to directly stare into the sun to measure its altitude. Despite these early beginnings, it would take many centuries before global navigation at sea became possible. Until the fifteenth century, mariners were essentially coastal navigators.

Sailing on the open sea was limited to regions of predictable winds and currents, or where there was a wide continental shelf to follow. Farther ventures were enabled by the development of scientifically and mathematically based methods and tools. Determining latitude can be accomplished relatively easily using celestial navigation. In the Northern Hemisphere, mariners could determine the latitude by measuring the altitude of the North Star above the horizon.

The angle in degrees was the latitude of the ship. One of the earliest human-made navigational tools used to aid mariners was the mariner's compass, which was an early form of the magnetic compass. Early mariners thought the mariner's compass was often inaccurate and inconsistent because they did not understand the concept of magnetic variation, which is the angle between true north geographic and magnetic north.

It was primarily used when the Sun was not visible to help identify the direction from which the wind was blowing. During the mid-thirteenth century, mariners began realizing that maps could be helpful and began keeping detailed records of their voyages. Thus, the first nautical charts were created. These first charts were not very accurate, but were considered valuable and often kept secret from other mariners. There was no latitude or longitude labeled on the charts, but between major ports there was a compass rose indicating the direction to travel.

The term "compass rose" comes from the figure's compass points, which resemble rose petals. Some of the early instruments used to assist sailors in determining latitude were the cross-staff, astrolabe, and quadrant. The astrolabe dates back to ancient Greece, when it was used by astronomers to help tell time, and was first used by mariners in the late Tall ships keep alive the history of ocean navigation.

Today, ships such as these call to mind images of merchant ships from long ago and pirates in their heyday during the eighteenth century. It was used to measure the altitude of the Sun and stars to determine latitude. This was the method used by Columbus and most other sailors of his era. In dead reckoning, the navigator finds his position by measuring the course and distance he has sailed from some known point.

Starting from a known point, the navigator measures out his course and distance from that point on a chart, pricking the chart with a pin to mark the new position. Each day's ending position would be the starting point for the next day's course-and-distance measurement. For this method to work the navigator needed a way to measure his course and to measure the distance sailed.

Course was measured by a magnetic compass, which had been known in Europe since at least Distance was determined by a time and speed calculation: the navigator multiplied the speed of the vessel by the time traveled to get the distance.

To determine speed on old sailing boats, sailors often used a log line. Describe how a log line was used and make a drawing of a log line on the back of this sheet. The fundamental flaw in using this log line method to determine distance is that it does not account for the effects of surface currents.

The log line method measures the speed of the ship relative to the surface water. It provides no means to estimate how fast the water itself flows. If a boat is carried westward by a strong current, the log line method will not reveal the existence of the current.

If you travel steadily on a train along a straight track, you will barely be aware that you are in motion relative to the tracks. How do you think a speedometer on a car measures speed? To determine their direction of travel, sailors used the compass. The compass is a magnet with ends labeled N and S. The N end points to the north magnetic pole of the Earth.

Include a drawing that shows the difference between geographic north and magnetic north. To plot their track on a map, sailors observed the heading or direction their ship traveled. They then compared their heading to the magnetic North direction revealed by a compass. Sailors were aware that the magnetic declination did not represent true north, so to compensate, they tried to map magnetic declinations around the globe.

North as measured by the compass typically is off by several degrees; this variation depends on location and changes over decades. Both the log line and the compass provided sailors with the means for deduced reckoning frequently abbreviated ded or dead reckoning so they could at least approximately reconstruct their travels.

On the ocean, this task is crucial for survival and success since there are few stable landmarks in a fluid environment. You may be accustomed to using deduced reckoning when you travel from one place to another. Write your answer in the space below. To practice and test your skills of measurement and deduced reckoning, try conducting a closed loop survey activity.

This activity can be done on a small desktop, as well as outside. Making measurements of your travels in a closed loop, where you end up at the point where you started provides a simple check of navigation methods.

If you come back to the same point, your measurements should determine a path that draws a closed loop. Sailors knew that surface currents affected the accuracy of their navigation predictions. They called the difference between their deduced and astronomically determined positions, ship drift. Astronomical determination of positions on Earth using the Sun and the stars is possible because the stars appear fixed and the Sun follows a cyclical, predictable motion.

The measured differences between positions determined by dead reckoning and astronomical methods provided the earliest estimates of ocean surface currents. The Astronomical Fix. As Earth rotates, the astronomical objects follow a path in the sky. The time they reach determined positions may be used to determine your longitude and latitude. Our Earth is a sphere, and angles are used to specify the location of sites on the surface of the Earth. In the east-west direction, one measures longitude with 0 o set at Greenwich, England.

Moving westward towards America , longitude angles are negative: between o and 0 o. In the north-south direction, one measures latitude with 0 o set at the equator of Earth. Northward towards the North Pole , positive latitude angles are between 0 o and 90 o. Southward towards the South Pole , negative latitude angles are between o and 0 o. Over the course of 24 hours, Earth rotates through degrees, and the stars appear to rotate in the opposite direction.

The positions of the stars, moon and Sun in the sky at any specific time, depends on your location. By carefully measuring both the positions of astronomical object positions and the times, you can find your latitude and longitude.

This is called an "astronomical fix". Solar noon is when the Sun is highest in the sky. However, because dead reckoning relies heavily on the past position of the ship, sailors could travel far off course if a small mistake was made in their calculations.

Additionally, dead reckoning does not account for ocean currents and wind, so ships using dead reckoning could still go astray even when their calculations were correct. Because early sailors lacked sophisticated navigation technology, recognizing navigational mistakes was also extremely difficult when using dead reckoning.

Beginning in ancient times, sailors used marine navigation tools to determine their speed, position and direction of travel.

While these tools were primitive at first, later advancements in math and science led to the development of more sophisticated navigation tools that greatly expanded the possibilities of sea travel.

Early tools that measured the angle of the stars and sun allowed sailors to determine their latitude based on how far these celestial bodies were from the horizon. Sailors could determine latitude easily with celestial navigation, but longitude could not be measured accurately until many centuries later, with the invention of the chronometer. This revolutionary technology, paired with existing tools for celestial navigation and a growing collection of accurate ocean charts, made it possible for explorers to travel throughout the world with precision and accuracy.

From the first seafarers to the rise of trade and exploration, these are some of the tools that shaped the history of navigation. One of the oldest navigation tools, leadlines were used to determine the depth of the water under the ship. A leadline is a long rope with a lead weight attached at the end. Sailors dropped the line and recorded how much line it took to reach the bottom of the ocean.

Viking sailors would measure the line based on the span of their arms as they hauled it back into the ship. These readings were called soundings and helped mariners navigate through inlets and along the coast.

During the 16th century, the invention of the chip log allowed sailors to calculate their approximate speed more accurately. A chip log is a line knotted at regular intervals and weighted at the end, so it drags in the water. To measure the speed of their ship, sailors dropped the line over the stern and counted the number of knots that went overboard during a certain period of time.

The chip log was an improvement on earlier methods for measuring speed while sailing, such as by dropping an object off the bow of the ship and counting how long it took to pass the stern of the ship.

The compass was one of the earliest navigational tools and continues to play a crucial role in marine navigation. Although it is not known when the compass was first invented, there are stories of Chinese armies using magnetized iron to direct their troops as early as the third millennium B. In the West, the first mention of a compass used for navigation at sea was in the 12th century by the Englishman Alexander Neckham.

Although early navigators still relied heavily on celestial navigation, compasses made it possible for sailors to navigate on overcast days when they could not see the sun or stars.

Early mariners compasses were made by placing a magnetized needle attached to a piece of wood into a bowl of water.

Later the needle was attached to a card marked with the wind rose that is still familiar on compasses today. Early sailors relied on written directions, or pilot books, to navigate between ports.