Mapping Toolbox™

almanac - Parameters for Earth, planets, Sun, and Moon

Syntax

almanac
almanac(body)
data = almanac(body,parameter)
data = almanac(body,parameter,units)
data = almanac(parameter,units,referencebody)

Description

almanac displays the names of the celestial objects available in the almanac.

almanac(body) lists the options, or parameters, available for each celestial body. Valid body strings are

'earth'				'pluto'
'jupiter'				'saturn'
'mars'				'sun'
'mercury'				'uranus'
'moon'				'venus'
'neptune'

data = almanac(body,parameter) returns the value of the requested parameter for the celestial body specified by body.

Valid parameter strings are 'radius' for the planetary radius, 'ellipsoid' or 'geoid' for the two-element ellipsoid vector, 'surfarea' for the surface area, and 'volume' for the planetary volume.

For the Earth, parameter can also be any valid predefined ellipsoid string. In this case, the two-element ellipsoid vector for that ellipsoid model is returned. Valid ellipsoid definition strings for the Earth are

For the Earth, the parameter strings 'ellipsoid' and 'geoid' are equivalent to'grs80'.

data = almanac(body,parameter,units) specifies the units to be used for the output measurement, where units is any valid distance units string. Note that these are linear units, but the result for surface area is in square units, and for volume is in cubic units. The default units are 'kilometers'.

data = almanac(parameter,units,referencebody) specifies the source of the information. This sets the assumptions about the shape of the celestial body used in the calculation of volumes and surface areas. A referencebody string of 'actual' returns a tabulated value rather than one dependent upon a ellipsoid model assumption. Other possible referencebody strings are 'sphere' for a spherical assumption and 'ellipsoid' for the default ellipsoid model. The default reference body is 'sphere'.

For the Earth, any of the preceding predefined ellipsoid definition strings can also be entered as a reference body.

For Mercury, Pluto, Venus, the Sun, and the Moon, the eccentricity of the ellipsoid model is zero, that is, the 'ellipsoid' reference body is actually a sphere.

Examples

The radius of the Earth (treated as a sphere) in kilometers is

almanac('earth','radius')

ans =
	6371

The default ellipsoid model for the Earth ([semimajor axis eccentricity]) is

almanac('earth','ellipsoid')

ans =
	1.0e+03 *
		6.3781    0.0001

Note that the radius returned for any ellipsoid model reference body is the semimajor axis:

almanac('earth','radius','kilometers','ellipsoid')

Warning: Semimajor axis returned for radius parameter
ans =
   6.3781e+03

Compare the tabulated values of the Earth's surface area with a spherical assumption and with the 1966 World Geodetic System ellipsoid model:

almanac('earth','surfarea','statutemiles','actual')

ans =
     1.969499232704451e+008

almanac('earth','surfarea','statutemiles','sphere')

ans =
     1.969362058529953e+008

almanac('earth','surfarea','statutemiles','wgs66')

ans =
     1.969371331484438e+008

Note that these values are so close that long notation is required to differentiate them.

Some lunar measurements are

almanac('moon','radius')

ans =
        1738

almanac('moon','surfarea')

ans =
   3.7959e+07

almanac('moon','volume')

ans =
   2.1991e+10

Remarks

Take care when using angular arc length units for distance measurements. All planets have a radius of 1 radian, for example, and an area unit of square degrees indicates unit squares, 1 degree of arc length on a side, not 1-degree-by-1-degree quadrangles.

See Also

distance

Functions — Alphabetical List

angl2str