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Navigation

What Is Navigation?

Navigation is the process of planning, recording, and controlling the movement of a craft or vehicle from one location to another. The word derives from the Latin roots navis ("ship") and agere ("to move or direct"). Geographic information—usually in the form of latitudes and longitudes—is at the core of navigation practice. The toolbox includes specialized functions for navigating across expanses of the globe, for which projected coordinates are of limited use.

Navigating on land, over water, and through the air can involve a variety of tasks:

  • Establishing position, using known, fixed landmarks (piloting)

  • Using the stars, sun, and moon (celestial navigation)

  • Using technology to fix positions (inertial guidance, radio beacons, and satellite navigation, including GPS)

  • Deducing net movement from a past known position (dead reckoning)

Another navigational task involves planning a voyage or flight, which includes determining an efficient route (usually by great circle approximation), weather avoidance (optimal track routing), and setting out a plan of intended movement (track laydown). Mapping Toolbox™ functions support these navigational activities as well.

Conventions for Navigational Functions

Units

You can use and convert among several angular and distance measurement units. The navigational support functions are

  • dreckon

  • gcwaypts

  • legs

  • navfix

To make these functions easy to use, and to conform to common navigational practice, for these specific functions only, certain conventions are used:

  • Angles are always in degrees.

  • Distances are always in nautical miles.

  • Speeds are always in knots (nautical miles per hour).

Related functions that do not carry this restriction include rhxrh, scxsc, gcxgc, gcxsc, track, timezone, and crossfix, because of their potential for application outside navigation.

Navigational Track Format

Navigational track format requires column-vector variables for the latitudes and longitudes of track waypoints. A waypoint is a point through which a track passes, usually corresponding to a course (or speed) change. Navigational tracks are made up of the line segments connecting these waypoints, which are called legs. In this format, therefore, n legs are described using n+1 waypoints, because an endpoint for the final leg must be defined. Mapping Toolbox navigation functions always presume angle units are always given in degrees.

Here, five track legs require six waypoints. In navigational track format, the waypoints are represented by two 6-by-1 vectors, one for the latitudes and one for the longitudes.

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