Navigational instruments refers to the instruments used by nautical navigators and pilots as tools of their trade. The purpose of navigation is to ascertain the present position and to determine the speed, direction etc. to arrive at the port or point of destination.

Charts and drafting instruments

• Charts
  Nautical chart
  A nautical chart is a graphic representation of a maritime area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land , natural features of the seabed, details of the coastline, navigational hazards, locations of natural and man-made aids...
  
  are maps of the areas to be navigated with details specific to the marine environment.
• Computing aids: used in the necessary mathematical calculations. Today electronic computers or calculators are used. Other traditional aids used included tables (trigonometric, logarithms, etc) and slide rules.
• Dividers used for measuring lengths of lines and approximate lengths of non-linear paths on a chart.
• Nautical almanac
  Nautical almanac
  A nautical almanac is a publication describing the positions of a selection of celestial bodies for the purpose of enabling navigators to use celestial navigation to determine the position of their ship while at sea...
  
  used to determine the position in the sky of a celestial body after a sight has been taken.
• Parallel rules
  Parallel rulers
  Parallel rulers are a drafting instrument used by navigators to draw parallel lines on charts. The tool consists of two straight edges joined by two arms which allow them to move closer or further away while always remaining parallel to each other.-History:...
  
  used for transferring a line to a parallel position. Also used to compare the orientation of a line to a magnetic or geographic orientation on a compass rose
  Compass rose
  A compass rose, sometimes called a windrose, is a figure on a compass, map, nautical chart or monument used to display the orientation of the cardinal directions — North, East, South and West - and their intermediate points. It is also the term for the graduated markings found on the traditional...
  
  .

Direct measuring

• Chip log
  Chip log
  A chip log, also called common log, ship log or just log, is a navigation tool used by mariners to estimate the speed of a vessel through water.-Construction:...
  
   and sand glass
  Hourglass
  An hourglass measures the passage of a few minutes or an hour of time. It has two connected vertical glass bulbs allowing a regulated trickle of material from the top to the bottom. Once the top bulb is empty, it can be inverted to begin timing again. The name hourglass comes from historically...
  
  serve to measure the ship's speed through the water
• Sounding line
  Sounding line
  A sounding line or lead line is a length of thin rope with a plummet, generally of lead, at its end. Regardless of the actual composition of the plummet, it is still called a "lead."...
  
  used to measure the depth of the water and to pick up samples from the bottom

Celestial navigation instruments

These instruments are used primarily to measure the elevation or altitude of a celestial object:

• Back staff, the best known of which is the Davis' quadrant. It could measure the altitude of the sun without having the navigator directly observe the sun.
• Cross staff, an older instrument long out of use.
• Kamal Very simple instrument used primarily by Arabian navigators. It consists of a small board with a knotted piece of twine through the center. The observer holds one of the knots in his mouth and extends the board away so that the edges make a constant angle with his eyes.
• Mariner's astrolabe
  Mariner's astrolabe
  The mariner's astrolabe, also called sea astrolabe, was an inclinometer used to determine the latitude of a ship at sea by measuring the sun's noon altitude or the meridian altitude of a star of known declination. Not an astrolabe proper, the mariner's astrolabe was rather a graduated circle with...
  
  Derived from the astrolabe
  Astrolabe
  An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and longitude, surveying, triangulation, and to...
  
  , it was developed in late 15th century and found use in the 16th to 17th centuries. It was replaced by the back staff and later by the octant
  Octant (instrument)
  The octant, also called reflecting quadrant, is a measuring instrument used primarily in navigation. It is a type of reflecting instrument.-Etymology:...
  
   and sextant
  Sextant
  A sextant is an instrument used to measure the angle between any two visible objects. Its primary use is to determine the angle between a celestial object and the horizon which is known as the altitude. Making this measurement is known as sighting the object, shooting the object, or taking a sight...
  
  .
• Quadrant
  Quadrant (instrument)
  A quadrant is an instrument that is used to measure angles up to 90°. It was originally proposed by Ptolemy as a better kind of astrolabe. Several different variations of the instrument were later produced by medieval Muslim astronomers.-Types of quadrants:...
  
  A very simple instrument which used a plumb bob.

These instruments are also used to measure the angular distance between objects:

• Octant
  Octant (instrument)
  The octant, also called reflecting quadrant, is a measuring instrument used primarily in navigation. It is a type of reflecting instrument.-Etymology:...
  
  , invented in 1731. The first widely-accepted instrument that could measure an angle without being strongly affected by movement.
• Sextant
  Sextant
  A sextant is an instrument used to measure the angle between any two visible objects. Its primary use is to determine the angle between a celestial object and the horizon which is known as the altitude. Making this measurement is known as sighting the object, shooting the object, or taking a sight...
  
  , derived from the octant in 1757, eventually made all previous instruments used for the same purpose obsolete.

Bearing instruments

• Pelorus
  Pelorus (instrument)
  In appearance and use, a pelorus resembles a compass or compass repeater, with sighting vanes or a sighting telescope attached, but it has no directive properties. That is, it remains at any relative direction to which it is set. It is generally used by setting 000° at the lubber's line. Relative...
  
  used to determine bearings relative to the ship's heading of landmarks, other ships, etc.

Compasses

• Bearing compass used to determine magnetic bearings of landmarks, other ships or celestial bodies.
• Magnetic compass used to determine the magnetic heading of the ship

Timekeeping

• Marine chronometer
  Marine chronometer
  A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...
  
  used to determine time at the prime meridian
  Prime Meridian
  The Prime Meridian is the meridian at which the longitude is defined to be 0°.The Prime Meridian and its opposite the 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.An international...
  
   with great precision which is necessary when reducing sights in celestial navigation
• Nocturnal
  Nocturnal (instrument)
  A nocturnal is an instrument used to determine the time based on the position of a certain star in the night sky. Sometimes called a "horologium nocturnum" or nocturlabe , it is closely related to the sun dial. A nocturnal is typically a navigational instrument...
  
  used to determine apparent local time by viewing the Polaris
  Polaris
  Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....
  
   and its surrounding stars.
• Ring dial or astronomical ring used to measure the height of a celestial body above the horizon. It could be used to find the altitude of the sun or determine local time. It let sunlight shine through a small orifice on the rim of the instrument. The point of light striking the far side of the instrument gave the altitude or tell time.

All those mentioned were the traditional instruments used until well into the second half of the 20th century. After WWII electronic aids to navigation developed very rapidly and, to a great extent, replaced more traditional tools. Electronic speed and depth finders have totally replaced their older counterparts. Radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 has become widespread even in small boats. Some Electronic aids to navigation like Loran

Loran

Loran may refer to:* LORAN, a terrestrial radio-based navigation system* Loran , a brand of blank audio cassette made of Lexan plastic...

 have already become obsolete themselves and have been replaced by GPS.

External links

• How to use the dividers
• How to use the parallel rulers