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departure

Departure of longitudes at specified latitudes

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    Syntax

    d = departure(lon1,lon2,lat)
    d = departure(lon1,lon2,lat,ellipsoid)
    d = departure(___,units)

    Description

    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.

    example

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

    Examples

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    Open Live Script

    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
    Open Live Script

    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

    • "radians" — Radians

    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.

    More About

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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

    See Also

    Functions