Package pygeodesy :: Module datum
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Module datum

Classes Datum, Ellipsoid and Transform and registries thereof.

Pure Python implementation of geodesy tools for ellipsoidal earth models, including datums and ellipsoid parameters for different geographic coordinate systems and methods for converting between them and to cartesian coordinates. Transcribed from JavaScript originals by (C) Chris Veness 2005-2016 and published under the same MIT Licence**, see http://www.movable-type.co.uk/ scripts/geodesy/docs/latlon-ellipsoidal.js.html.

Historical geodetic datums: a latitude/longitude point defines a geographic location on or above/below the earth’s surface, measured in degrees from the equator and the International Reference Meridian and meters above the ellipsoid, and based on a given datum. The datum is based on a reference ellipsoid and tied to geodetic survey reference points.

Modern geodesy is generally based on the WGS84 datum (as used for instance by GPS systems), but previously various reference ellipsoids and datum references were used.

The UK Ordnance Survey National Grid References are still based on the otherwise historical OSGB36 datum, q.v. Ordnance Survey 'A guide to coordinate systems in Great Britain' Section 6 http://www.ordnancesurvey .co.uk/docs/support/guide-coordinate-systems-great-britain.pdf and also http://www.ordnancesurvey.co.uk/blog/2014/12/2.


Version: 17.06.21

Classes
  Ellipsoid
Ellipsoid with semi-major, semi-minor axis, inverse flattening and a number of other pre-computed, frequently used values.
  Transform
Helmert transformation.
  Datum
Ellipsoid and transform parameters for an earth model.
Variables
  R_M = 6371008.77141
Mean, spherical earth radius (meter).
  R_KM = 6371.00877142
Mean, spherical earth radius (kilo meter).
  R_NM = 3440.06953447
Mean, spherical earth radius (nautical miles).
  R_SM = 3958.75339537
Mean, spherical earth radius (statute miles).
  Datums = Datums.BD72: Datum(name='BD72', ellipsoid=Ellipsoids....
Registered datums (_Enum).
  Ellipsoids = Ellipsoids.Airy1830: Ellipsoid(name='Airy1830', a...
Registered ellipsoids (_Enum).
  Transforms = Transforms.BD72: Transform(name='BD72', tx=106.86...
Registered transforms (_Enum).
Variables Details

Datums

Registered datums (_Enum).

Value:
Datums.BD72: Datum(name='BD72', ellipsoid=Ellipsoids.Intl1924, transfo\
rm=Transforms.BD72)
Datums.DHDN: Datum(name='DHDN', ellipsoid=Ellipsoids.Bessel1841, trans\
form=Transforms.DHDN)
Datums.ED50: Datum(name='ED50', ellipsoid=Ellipsoids.Intl1924, transfo\
rm=Transforms.ED50)
Datums.GRS80: Datum(name='GRS80', ellipsoid=Ellipsoids.GRS80, transfor\
m=Transforms.WGS84)
...

Ellipsoids

Registered ellipsoids (_Enum).

Value:
Ellipsoids.Airy1830: Ellipsoid(name='Airy1830', a=6377563.396, b=63562\
56.909, f_=299.3249646, f=0.00334085, e2=0.00667054, e22=0.00671533, R\
=6370461.23366667, Rm=6366901.23988196, R2=6370459.65458944, R3=637045\
3.30986645, Rr=6366914.60880589)
Ellipsoids.AiryModified: Ellipsoid(name='AiryModified', a=6377340.189,\
 b=6356034.448, f_=299.3249646, f=0.00334085, e2=0.00667054, e22=0.006\
71533, R=6370238.27533333, Rm=6366678.40619415, R2=6370236.69636116, R\
3=6370230.35181066, Rr=6366691.7746498)
...

Transforms

Registered transforms (_Enum).

Value:
Transforms.BD72: Transform(name='BD72', tx=106.8686, ty=-52.2978, tz=1\
03.7239, rx=-0.0, ry=-0.0, rz=-0.0, s=1.2727, s1=1.0, sx=-0.3366, sy=-\
0.457, sz=-1.8422)
Transforms.Bessel1841: Transform(name='Bessel1841', tx=-582.0, ty=-105\
.0, tz=-414.0, rx=-0.0, ry=-0.0, rz=0.0, s=-8.3, s1=1.0, sx=-1.04, sy=\
-0.35, sz=3.08)
Transforms.Clarke1866: Transform(name='Clarke1866', tx=8.0, ty=-160.0,\
 tz=-176.0, rx=0, ry=0, rz=0, s=0, s1=1, sx=0, sy=0, sz=0)
...