CAA NZ Instrument Rating Navigation key terms

The speed of an aircraft through the air mass, corrected for altitude and temperature effects on the airspeed indicator. Used with wind to calculate groundspeed and leg timing.

The uncorrected speed shown on the airspeed indicator, affected by instrument, position and compressibility errors. It is the starting point for deriving calibrated and true airspeed.

Indicated airspeed corrected for instrument and position error. It approximates true airspeed at sea level in standard conditions and feeds into TAS calculations.

The speed of the aircraft over the ground, being true airspeed adjusted for the wind component along track. It determines time en route and fuel used.

A vector diagram combining true airspeed, wind velocity and groundspeed to solve heading and drift. It is the core calculation for dead reckoning navigation planning.

The direction the aircraft nose points, measured in degrees from a reference such as magnetic north. It differs from track by the drift angle.

The actual path of the aircraft over the ground, expressed as a direction in degrees. It results from heading combined with wind drift.

The angular difference between heading and track caused by the crosswind component. It is applied as a wind correction angle to hold a desired track.

The angle applied to a desired track to counter drift and produce the heading that keeps the aircraft on track. It is calculated from the crosswind component and TAS.

The angular difference between true north and magnetic north at a given location, shown on charts as isogonals. It converts true directions to magnetic and is subject to annual change.

The error of a magnetic compass caused by the aircraft's own magnetic fields, varying with heading. It is recorded on a compass correction card and applied to obtain magnetic heading.

The heading referenced to magnetic north, obtained by applying variation to true heading. It is the value used for most airborne navigation and ATC reporting.

The heading actually indicated by the aircraft magnetic compass after deviation is applied to magnetic heading. It is what the pilot steers in the cockpit.

A line on a chart joining points of equal magnetic variation. Pilots use it to determine the local variation for converting between true and magnetic directions.

Navigation by calculating position from a known starting point using heading, airspeed, wind and time. It requires no external fixes but accumulates error over time.

Navigation by visual reference to landmarks and chart features. It is often combined with dead reckoning and is limited by visibility and identifiable ground features.

A confirmed aircraft position determined from external references such as visual landmarks, radio aids or satellite systems. It resets the dead reckoning position and limits accumulated error.

A line on which the aircraft is known to lie, derived from a bearing, distance or visual observation. Two or more intersecting position lines establish a fix.

The direction of one point from another, measured in degrees from a stated reference such as true or magnetic north. It is fundamental to radio aid tracking and position plotting.

A magnetic bearing extending outward from a VOR station. Aircraft track or intercept radials to navigate along defined airways and to fix position.

A ground-based radio navigation aid transmitting radials that allow aircraft to determine bearing from the station. It supports tracking, position fixing and airway navigation.

A radio system measuring slant range from the aircraft to a ground transponder, displayed in nautical miles. It pairs with VOR or ILS to give distance and position.

The straight-line distance from the aircraft to a ground station, as measured by DME. It exceeds the horizontal ground distance, with the error greatest at high altitude and close range.

A ground station transmitting an omnidirectional signal that an aircraft ADF uses to determine the bearing to the station. It is simple but subject to static and night-effect errors.

Airborne equipment that indicates the relative bearing of an NDB or other radio source. Combined with heading, it gives the magnetic bearing to the station.

The angle between the aircraft's heading and the direction to a radio station, measured clockwise from the nose. Adding it to heading gives the magnetic bearing to the station.

A satellite-based system providing position, velocity and time worldwide. In aviation it supports area navigation, approach guidance and position fixing, subject to integrity monitoring.

A navigation specification requiring onboard performance monitoring and alerting, with a defined lateral accuracy value such as RNP 1. It permits precise track-keeping in designated airspace.

Navigation along any desired path using waypoints rather than direct station-to-station tracking. It relies on onboard computing and sensors such as GNSS, VOR/DME or inertial systems.

A defined geographic point, identified by coordinates or a named fix, used to build a navigation route. Waypoints anchor RNAV legs and flight-planned tracks.

A map depicting navigation information such as airspace, tracks, radio aids, terrain and obstacles. Charts are drawn to a stated scale and projection for flight planning and in-flight navigation.

A cylindrical chart projection on which meridians are parallel and the rhumb line plots as a straight line. Scale expands with latitude, so it suits equatorial and mid-latitude navigation.

A conical projection on which great circles plot approximately as straight lines and scale is nearly constant across the chart. It is widely used for aeronautical charts in mid-latitudes.

The shortest path between two points on the Earth's surface, forming an arc of a plane through the Earth's centre. Its direction changes along the route except along the equator or a meridian.

A path crossing every meridian at the same angle, shown as a straight line on a Mercator chart. It is easier to steer than a great circle but not the shortest distance.

A unit of distance equal to one minute of latitude, approximately 1,852 metres. It is the standard unit for air navigation distances, speeds and fuel planning.

A speed of one nautical mile per hour. Airspeeds, groundspeeds and wind velocities in aviation are normally expressed in knots.

The pressure value set on the altimeter subscale to reference indicated altitude to a datum such as QNH, QFE or standard pressure. Correct setting is essential for terrain clearance and separation.

The altitude below which the altimeter is set to local pressure and above which flight levels on standard pressure are used. It marks the changeover in altimeter setting procedures.

An altitude expressed in hundreds of feet referenced to standard pressure of 1013.2 hPa. Flight levels provide a common datum for vertical separation above the transition altitude.