Mapping Toolbox

almanac

Display planetary data for the nine planets, the Sun, and the Moon

Syntax

• almanac
  almanac(body)
  data = almanac(body,parameter)
  data = almanac(body,parameter,units)
  data = almanac(body,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, 'geoid' for the two-element geoid 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 geoid vector for that ellipsoid model is returned. Valid ellipsoid definition strings for the Earth are:

'everest'	for the 1830 Everest ellipsoid
'bessel'	for the 1841 Bessel ellipsoid
'airy'	for the 1849 Airy ellipsoid
'clarke66'	for the 1866 Clarke ellipsoid
'clarke80'	for the 1880 Clarke ellipsoid
'international'	for the 1924 International ellipsoid
'krasovsky'	for the 1940 Krasovsky ellipsoid
'wgs60'	for the 1960 World Geodetic System ellipsoid
'iau65'	for the 1965 International Astronomical Union ellipsoid
'wgs66'	for the 1966 World Geodetic System ellipsoid
'iau68'	for the 1968 International Astronomical Union ellipsoid
'wgs72'	for the 1972 World Geodetic System ellipsoid
'grs80'	for the 1980 Geodetic Reference System ellipsoid

For the Earth, the parameter string 'geoid' is 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 geoid model assumption. Other possible referencebody strings are 'sphere' for a spherical assumption, and 'geoid', for the default geoid model. The default reference body is 'sphere'.

For the Earth, any of the above-listed pre-defined ellipsoid definition strings can also be entered as a reference body.

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

Examples

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

• almanac('earth','radius')
  ans =
      6371
  

The default geoid model for the Earth ([semimajor axis eccentricity]):

• almanac('earth','geoid')
  ans =
      1.0e+03 *
          6.3781    0.0001
  

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

• almanac('earth','radius','kilometers','geoid')
  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 =
       1.969614809100133e+08
  
  almanac('earth','surfarea','statutemiles','sphere')
  ans =
       1.969477626875824e+08
  
  almanac('earth','surfarea','statutemiles','wgs66')
  ans =
       1.969486900374475e+08
  

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

Some lunar measurements:

• almanac('moon','radius')
  ans =
          1738
  
  almanac('moon','surfarea')
  ans =
     3.7959e+07
  
  almanac('moon','volume')
  ans =
     2.1991e+10
  

Remarks

Care should be taken 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	Distance between points
distdim	Convert distance units
geoid vector	Data structure for geoid model

Mapping Toolbox Demos

angl2str