Geodetic::Coordinate::NED - North, East, Down¶

Overview¶

NED (North, East, Down) is a local tangent plane coordinate system commonly used in aviation and navigation. It defines positions relative to a local reference point on the Earth's surface, with axes pointing North, East, and Down.

Constructor¶

NED.new(n: 0.0, e: 0.0, d: 0.0)

All parameters are in meters.

Attribute Aliases¶

Primary	Alias
`n`	`north`
`e`	`east`
`d`	`down`

Reference Point¶

NED is a local coordinate system. Conversions to and from global coordinate systems (such as LLA or ECEF) require a reference point specified as an LLA coordinate. This reference point defines the origin of the local tangent plane.

The one exception is the conversion between NED and ENU, which does not require a reference point.

Conversions¶

Direct (no reference point needed)¶

NED <-> ENU — A simple axis remap:
```
NED(n, e, d) <-> ENU(e, n, -d)
```

Via reference point¶

NED -> LLA — Requires a reference LLA.
NED -> ECEF — Requires a reference LLA.

Methods¶

Method	Description
`horizontal_distance_to(other)`	Horizontal (N-E plane) distance to another NED point (meters)
`local_bearing_to(other)`	Bearing from this point to another NED point (degrees from north, 0-360)
`local_elevation_angle_to(other)`	Elevation angle from this point to another NED point (degrees)
`distance_to_origin`	Euclidean distance from this point to the origin (meters)
`elevation_angle`	Elevation angle from the origin to this point (degrees)
`bearing_from_origin`	Bearing from the origin to this point (degrees from north, 0-360)
`horizontal_distance_to_origin`	Horizontal distance from this point to the origin (meters)

Universal Distance and Bearing Methods¶

NED is a relative coordinate system. The universal distance_to, straight_line_distance_to, bearing_to, and elevation_to methods raise ArgumentError because NED cannot be converted to an absolute system without a reference point. Convert to an absolute system first:

ref = Geodetic::Coordinate::LLA.new(lat: 47.62, lng: -122.35, alt: 0.0)
lla = ned.to_lla(ref)
lla.distance_to(other_lla)   # Vincenty great-circle distance
lla.bearing_to(other_lla)    # Great-circle forward azimuth (Bearing object)

Bearing Convention¶

Bearing is measured in degrees from north, clockwise, in the range 0-360.

Example¶

point = Geodetic::Coordinate::NED.new(n: 200.0, e: 100.0, d: -50.0)

point.north  # => 200.0
point.east   # => 100.0
point.down   # => -50.0

point.distance_to_origin            # => Euclidean distance in meters
point.bearing_from_origin           # => Bearing in degrees from north
point.elevation_angle               # => Elevation angle in degrees
point.horizontal_distance_to_origin # => Horizontal distance in meters