# departure

Departure of longitudes at specified latitudes

## Description

example

d = departure(lon1,lon2,lat) calculates the departure from lon1 to lon2 at the latitude lat. Departure is the distance along a specific parallel between two meridians. This syntax references the coordinates to the unit sphere and returns d as a spherical distance in degrees.

example

d = departure(lon1,lon2,lat,ellipsoid) specifies a reference ellipsoid for the coordinates. This syntax returns d in the units of the semimajor axis of the reference ellipsoid.

d = departure(___,units) specifies the angle units, in addition to any combination of input arguments from the previous syntaxes.

## Examples

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Calculate the departure distance between the longitudes 10ºW and 20ºW at the latitudes 10ºN, 40ºN, and 80ºN. By default, the departure function returns spherical distances in degrees.

lon1 = 10;
lon2 = 20;
d1 = departure(lon1,lon2,10)
d1 = 9.8481

d2 = departure(lon1,lon2,40)
d2 = 7.6604

d3 = departure(lon1,lon2,80)
d3 = 1.7365

Create a World Geodetic System of 1984 (WGS84) reference ellipsoid with a length unit of nautical miles.

wgs84 = wgs84Ellipsoid("nm");

Calculate the departure distance between the longitudes 10ºW and 20ºW at the latitudes 10ºN, 40ºN, and 80ºN. Reference the coordinates to the ellipsoid. When you specify a reference ellipsoid as input to the departure function, the function returns linear distances in the units of the semimajor axis of the ellipsoid.

lon1 = 10;
lon2 = 20;
d1 = departure(lon1,lon2,10,wgs84)
d1 = 592.0052

d2 = departure(lon1,lon2,40,wgs84)
d2 = 461.0899

d3 = departure(lon1,lon2,80,wgs84)
d3 = 104.7164

## Input Arguments

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Longitude of the first point, specified as a scalar or array.

The sizes of lon1, lon2, and lat must match.

Data Types: single | double

Longitude of the second point, specified as a scalar or array.

The sizes of lon1, lon2, and lat must match.

Data Types: single | double

Latitude of the points, specified as a scalar or array.

The sizes of lon1, lon2, and lat must match.

Data Types: single | double

Reference ellipsoid, specified as a referenceSphere object, a referenceEllipsoid object, an oblateSpheroid object, or a two-element vector of the form [semimajor_axis eccentricity], where semimajor_axis is the length of the semimajor axis and eccentricity is the eccentricity. The values semimajor_axis and eccentricity must be of data type double.

The default value of [1 0] represents the unit sphere.

Angle unit, specified as one of these options:

• "degrees" — Degrees

If you do not specify a reference ellipsoid, this argument determines the angle units for the coordinates and the departure (as a spherical distance). If you specify a reference ellipsoid, this argument only determines the angle units for the coordinates.

Data Types: char | string

## Output Arguments

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Departure distance, returned as a scalar or an array of the same size as lon1, lon2, and lat.

• When you do not specify a reference ellipsoid as input, d is a spherical distance in degrees. You can return a spherical distance in radians by using the units input argument.

• When you specify a reference ellipsoid as input, d is a linear distance in the units of the semimajor axis of the ellipsoid.

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### Departure

Departure is the distance along a parallel between two points. Whereas a degree of latitude is always the same distance, a degree of longitude is different in length at different latitudes. In practice, this distance is usually given in nautical miles.

## Version History

Introduced before R2006a