Waypoint
Waypoints have traditionally been associated with distinctive features of the real world, such as rock formations, springs, oases, mountains, buildings, roadways, waterways, railways, and so on.
For example, artificial airways "highways in the sky", created specifically for purposes of air navigation, often have no clear connection to features of the real world, and consist only of a series of abstract waypoints in the sky through which pilots navigate; these airways are designed to facilitate air traffic control and routing of traffic between heavily traveled locations, and do not reference natural terrain features.
Abstract waypoints of this kind have been made practical by modern navigation technologies, such as land-based radio beacons and the satellite-based GPS.
Abstract waypoints typically have only specified longitude and latitude or UTM coordinates plus the reference datum, and often a name if they are marked on charts, and are located using a radio navigation system such as a VOR or GPS receiver.
[3] A typical GPS receiver can locate a waypoint with an accuracy of three meters or better when used with land-based assisting technologies such as the Wide Area Augmentation System (WAAS).
Some GPS systems intended for automobile navigation can generate a suggested driving route between two waypoints, based on the cartographic database.
The best of these systems can take into account traffic restrictions such as one-way streets and intersections where left or right turns are prohibited when computing the suggested driving route.
These include standard map symbols for marine navigation aids such as buoys, marinas and anchorages, as well as land-based landmarks such as churches, bridges, shopping centers, parks and tunnels.
These references comprise the National Airspace System's method of allowing air traffic to select routes that yield efficient point-to-point navigation.
In air navigation, waypoints are sometimes defined as intersections between two VOR radials or NDB bearings, or in terms of specific distances and headings towards or away from a radio beacon.
Temporary waypoints are sometimes defined as traffic requires, e.g., air-traffic controllers may instruct a pilot to reference a terrain feature at "your ten o'clock position, two miles."
