Fix (position) in the context of "Geographic position"

A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.

The estimation of this angle, the altitude, is known as sighting or shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart—for example, sighting the Sun at noon or Polaris at night (in the Northern Hemisphere) to estimate latitude (with sight reduction). Sighting the height of a landmark can give a measure of distance off and, held horizontally, a sextant can measure angles between objects for a position on a chart. A sextant can also be used to measure the lunar distance between the moon and another celestial object (such as a star or planet) in order to determine Greenwich Mean Time and hence longitude.

In navigation, dead reckoning is the process of calculating the current position of a moving object by using a previously determined position, or fix, and incorporating estimates of speed, heading (or direction or course), and elapsed time. The corresponding term in biology, to describe the processes by which animals update their estimates of position or heading, is path integration.

Advances in navigational aids that give accurate information on position, in particular satellite navigation using the Global Positioning System, have made simple dead reckoning by humans obsolete for most purposes. However, inertial navigation systems, which provide very accurate directional information, use dead reckoning and are very widely applied.

In aviation, an intersection is a virtual navigational fix that helps aircraft maintain their flight plan. It is usually defined as the intersection (in the geometrical sense) of two VOR (VHF Omnidirectional Range) radials. They are usually identified as major airway intersections where aircraft, operating under instrument flight rules, often change direction of flight while en route. According to the Federal Aviation Regulations, some intersections are designated as mandatory reporting points for pilots who are not in radar contact with air traffic control.

Intersections also play an important role in departure and approach procedures. All intersections have an alphabetical or alphanumeric designation. Near major airports, the intersection designation code typically consists of three letters followed by the runway number. Most other intersection designations consist of five-letter combinations that are either pronounceable or chosen for their mnemonic value, since either air traffic control or the flight plan may require the pilot to announce the designation. In the terminal procedure or approach plate example to the right, note that two of the intersections are called DONUT and KOFFE. Many intersections are named because of local points of interest. In the case of Carroll County Airport, there is a popular diner located on the field to which many pilots fly.

Submarine navigation underwater requires special skills and technologies not needed by surface ships. The challenges of underwater navigation have become more important as submarines spend more time underwater, travelling greater distances and at higher speed. Military submarines travel underwater in an environment of total darkness with neither windows nor lights. Operating in stealth mode, they cannot use their active sonar systems to ping ahead for underwater hazards such as undersea mountains, drilling rigs or other submarines. Surfacing to obtain navigational fixes is precluded by pervasive anti-submarine warfare detection systems such as radar and satellite surveillance. Antenna masts and antenna-equipped periscopes can be raised to obtain navigational signals but in areas of heavy surveillance, only for a few seconds or minutes; current radar technology can detect even a slender periscope while submarine shadows may be plainly visible from the air.

A position line or line of position (LOP) is a line (or, on the surface of the Earth, a curve) that can be both identified on a chart (nautical chart or aeronautical chart) and translated to the surface of the Earth. The intersection of a minimum of two position lines is a fix that is used in position fixing to identify a navigator's location.

Piloting or pilotage is the process of navigating on water or in the air using fixed points of reference on the sea or on land, usually with reference to a nautical chart or aeronautical chart to obtain a fix of the position of the vessel or aircraft with respect to a desired course or location. Horizontal fixes of position from known reference points may be obtained by sight or by radar. Vertical position may be obtained by depth sounder to determine depth of the water body below a vessel or by altimeter to determine an aircraft's altitude, from which its distance above the ground can be deduced. Piloting a vessel is usually practiced close to shore or on inland waterways. Pilotage of an aircraft is practiced under visual meteorological conditions for flight.

Land navigation is a related discipline, using a topographic map, especially when applied over trackless terrain. Divers use related techniques for underwater navigation.