API Reference¶

`geodesy.datum` Module¶

Geodetic datum definitions.

A datum defines the position and orientation of a reference ellipsoid relative to the Earth.

class geodesy.datum.HelmertParameters(tx, ty, tz, rx, ry, rz, s)¶

Bases: object

7-parameter Helmert transformation (Bursa-Wolf) to WGS84.

tx¶

Translation along X-axis in metres.

Type:: float

ty¶

Translation along Y-axis in metres.

Type:: float

tz¶

Translation along Z-axis in metres.

Type:: float

rx¶

Rotation around X-axis in arc-seconds.

Type:: float

ry¶

Rotation around Y-axis in arc-seconds.

Type:: float

rz¶

Rotation around Z-axis in arc-seconds.

Type:: float

s¶

Scale factor in parts per million (ppm).

Type:: float

Example

>>> OSGB36.to_wgs84.tx
446.448

class geodesy.datum.Datum(name, code, ellipsoid, to_wgs84=None, remarks=None)¶

Bases: object

A geodetic datum for coordinate reference systems.

name¶

Human-readable name.

Type:: str

code¶

EPSG code.

Type:: int

ellipsoid¶

Reference ellipsoid.

Type:: geodesy.ellipsoid.Ellipsoid

to_wgs84¶

Helmert transformation parameters to WGS84, if applicable.

Type:: geodesy.datum.HelmertParameters | None

remarks¶

Remarks, if any.

Type:: str | None

Example

>>> WGS84.ellipsoid.a
6378137.0
>>> WGS84.urn
'urn:ogc:def:datum:EPSG::6326'

property urn: str¶: Uniform Resource Name (URN).

geodesy.datum.ED50 = Datum(name='European Datum 1950', code=6230, ellipsoid=Ellipsoid(name='International 1924', code=7022, a=6378388.0, f=0.003367003367003367, remarks='Adopted by IUGG 1924 in Madrid. Based on Hayford 1909/1910 figures.'), to_wgs84=HelmertParameters(tx=-87.0, ty=-98.0, tz=-121.0, rx=0.0, ry=0.0, rz=0.0, s=0.0), remarks=None)¶: European Datum 1950 (EPSG:6230). Uses International 1924 ellipsoid.

geodesy.datum.ETRS89 = Datum(name='European Terrestrial Reference System 1989 ensemble', code=6258, ellipsoid=Ellipsoid(name='GRS 1980', code=7019, a=6378137.0, f=0.003352810681182319, remarks="Adopted by IUGG 1979 Canberra. Inverse flattening is derived from geocentric gravitational constant GM = 3986005e8 m*m*m/s/s; dynamic form factor J2 = 108263e-8 and Earth's angular velocity = 7292115e-11 rad/s."), to_wgs84=HelmertParameters(tx=0.0, ty=0.0, tz=0.0, rx=0.0, ry=0.0, rz=0.0, s=0.0), remarks="Has been realized through ETRF89, ETRF90, ETRF91, ETRF92, ETRF93, ETRF94, ETRF96, ETRF97, ETRF2000, ETRF2005, ETRF2014 and ETRF2020. This 'ensemble' covers any or all of these realizations without distinction.")¶: European Terrestrial Reference System 1989 (EPSG:6258), coincident with WGS84 at epoch 1989.0. Uses GRS 1980 ellipsoid.

geodesy.datum.NAD27 = Datum(name='North American Datum 1927', code=6267, ellipsoid=Ellipsoid(name='Clarke 1866', code=7008, a=6378206.4, f=0.0033900753039287934, remarks="Original definition a=20926062 and b=20855121 (British) feet. Uses Clarke's 1865 inch-metre ratio of 39.370432 to obtain metres. (Metric value then converted to US survey feet for use in the US and international feet for use in Cayman Islands)."), to_wgs84=HelmertParameters(tx=-8.0, ty=160.0, tz=176.0, rx=0.0, ry=0.0, rz=0.0, s=0.0), remarks='In United States (USA) and Canada, replaced by North American Datum 1983 (NAD83) (code 6269) ; in Mexico, replaced by Mexican Datum of 1993 (code 1042).')¶: North American Datum 1927 (EPSG:6267). Uses Clarke 1866 ellipsoid.

geodesy.datum.NAD83 = Datum(name='North American Datum 1983', code=6269, ellipsoid=Ellipsoid(name='GRS 1980', code=7019, a=6378137.0, f=0.003352810681182319, remarks="Adopted by IUGG 1979 Canberra. Inverse flattening is derived from geocentric gravitational constant GM = 3986005e8 m*m*m/s/s; dynamic form factor J2 = 108263e-8 and Earth's angular velocity = 7292115e-11 rad/s."), to_wgs84=HelmertParameters(tx=0.0, ty=0.0, tz=0.0, rx=0.0, ry=0.0, rz=0.0, s=0.0), remarks='Although the 1986 adjustment included connections to Greenland and Mexico, it has not been adopted there. In Canada and US, replaced NAD27.')¶: North American Datum 1983 (EPSG:6269), coincident with WGS84 within original realization accuracy. Uses GRS 1980 ellipsoid.

geodesy.datum.OSGB36 = Datum(name='Ordnance Survey of Great Britain 1936', code=6277, ellipsoid=Ellipsoid(name='Airy 1830', code=7001, a=6377563.396, f=0.0033408506414970775, remarks='Original definition is a=20923713, b=20853810 feet of 1796. 1/f is given to 7 decimal places. For the 1936 retriangulation OSGB defines the relationship of 10 feet of 1796 to the International metre through ([10^0.48401603]/10) exactly = 0.3048007491...'), to_wgs84=HelmertParameters(tx=446.448, ty=-125.157, tz=542.06, rx=0.1502, ry=0.247, rz=0.8421, s=-20.4894), remarks='The average accuracy of OSTN compared to the old triangulation network (down to 3rd order) is 0.1m. With the introduction of OSTN15, the area for OGSB36 has effectively been extended from Britain to cover the adjacent UK Continental Shelf.')¶: Ordnance Survey of Great Britain 1936 (EPSG:6277). Uses Airy 1830 ellipsoid.

geodesy.datum.WGS84 = Datum(name='World Geodetic System 1984 ensemble', code=6326, ellipsoid=Ellipsoid(name='WGS 84', code=7030, a=6378137.0, f=0.0033528106647474805, remarks="1/f derived from four defining parameters semi-major axis; C20 = -484.16685*10e-6; earth's angular velocity ω = 7292115e-11 rad/sec; gravitational constant GM = 3986005e8 m*m*m/s/s. In 1994 new GM = 3986004.418e8 m*m*m/s/s but a and 1/f retained."), to_wgs84=HelmertParameters(tx=0.0, ty=0.0, tz=0.0, rx=0.0, ry=0.0, rz=0.0, s=0.0), remarks='EPSG::6326 has been the then current realization. No distinction is made between the original and subsequent (G730, G873, G1150, G1674, G1762, G2139 and G2296) WGS 84 frames. Since 1997, WGS 84 has been maintained within 10cm of the then current ITRF.')¶: World Geodetic System 1984 (EPSG:6326), the global reference datum for GPS. Uses WGS 84 datum.

`geodesy.ellipsoid` Module¶

Reference ellipsoid definitions.

An ellipsoid is defined by its semi-major axis (a) and flattening (f). All other parameters are derived from these.

class geodesy.ellipsoid.Ellipsoid(name, code, a, f, remarks=None)¶

Bases: object

A reference ellipsoid for geodetic calculations.

name¶

Human-readable name

Type:: str

code¶

EPSG code

Type:: int

a¶

Semi-major axis in metres

Type:: float

f¶

Flattening (dimensionless)

Type:: float

remarks¶

Remarks, if any

Type:: str | None

Example

>>> WGS_84.a
6378137.0
>>> WGS_84.b  # semi-minor axis (derived)
6356752.314245179

property b: float¶: Semi-minor axis in metres.

property e2: float¶: First eccentricity squared.

property e: float¶: First eccentricity.

property ep2: float¶: Second eccentricity squared.

property urn: str¶: Uniform Resource Name (URN).

geodesy.ellipsoid.AIRY_1830 = Ellipsoid(name='Airy 1830', code=7001, a=6377563.396, f=0.0033408506414970775, remarks='Original definition is a=20923713, b=20853810 feet of 1796. 1/f is given to 7 decimal places. For the 1936 retriangulation OSGB defines the relationship of 10 feet of 1796 to the International metre through ([10^0.48401603]/10) exactly = 0.3048007491...')¶: Airy 1830 ellipsoid (EPSG:7001). Used by OSGB36 datum.

geodesy.ellipsoid.CLARKE_1866 = Ellipsoid(name='Clarke 1866', code=7008, a=6378206.4, f=0.0033900753039287934, remarks="Original definition a=20926062 and b=20855121 (British) feet. Uses Clarke's 1865 inch-metre ratio of 39.370432 to obtain metres. (Metric value then converted to US survey feet for use in the US and international feet for use in Cayman Islands).")¶: Clarke 1866 ellipsoid (EPSG:7008). Used by NAD27 datum.

geodesy.ellipsoid.GRS_1980 = Ellipsoid(name='GRS 1980', code=7019, a=6378137.0, f=0.003352810681182319, remarks="Adopted by IUGG 1979 Canberra. Inverse flattening is derived from geocentric gravitational constant GM = 3986005e8 m*m*m/s/s; dynamic form factor J2 = 108263e-8 and Earth's angular velocity = 7292115e-11 rad/s.")¶: GRS 1980 ellipsoid (EPSG:7019). Used by NAD83 and ETRS89 datums.

geodesy.ellipsoid.INTERNATIONAL_1924 = Ellipsoid(name='International 1924', code=7022, a=6378388.0, f=0.003367003367003367, remarks='Adopted by IUGG 1924 in Madrid. Based on Hayford 1909/1910 figures.')¶: International 1924 ellipsoid (EPSG:7022), also known as Hayford 1909. Used by ED50 datum.

geodesy.ellipsoid.WGS_84 = Ellipsoid(name='WGS 84', code=7030, a=6378137.0, f=0.0033528106647474805, remarks="1/f derived from four defining parameters semi-major axis; C20 = -484.16685*10e-6; earth's angular velocity ω = 7292115e-11 rad/sec; gravitational constant GM = 3986005e8 m*m*m/s/s. In 1994 new GM = 3986004.418e8 m*m*m/s/s but a and 1/f retained.")¶: WGS 84 ellipsoid (EPSG:7030). Used by WGS84 datum.

API Reference¶

geodesy.datum Module¶

geodesy.ellipsoid Module¶

`geodesy.datum` Module¶

`geodesy.ellipsoid` Module¶