Constants

This module contains constants commonly used in geodetic calculations, including ellipsoids, projections and transformations.

Classes

GeodePy provides four classes for handling commonly used geodetic constants. These include a class for ellipsoids, projections, tranformations and tranformations sigmas. These classes can be used to create objects that store the relevant parameters for each type of constant, and provide methods for accessing and manipulating these parameters.

class geodepy.constants.Ellipsoid(semimaj, inversef)

Ellipsoid Parameters

Parameters:

• semimaj – Semi-major axis (m)

• inversef – Inverse flattening

class geodepy.constants.Projection(falseeast, falsenorth, cmscale, zonewidth, initialcm)

Transverse Mercator Projection Parameters

Parameters:

• falseeast – Easting (m) assigned to Central Meridian

• falsenorth – Northing (m) assigned to Equator

• cmscale – Central Meridian Scale Factor (unitless, 1 is no scale)

• zonewidth – Width (decimal degrees) of each TM Zone

• initialcm – Longitude (decimal degrees) of TM Zone 1

class geodepy.constants.Transformation(from_datum, to_datum, ref_epoch, tx, ty, tz, sc, rx, ry, rz, d_tx=0.0, d_ty=0.0, d_tz=0.0, d_sc=0.0, d_rx=0.0, d_ry=0.0, d_rz=0.0, tf_sd=None)

Transformation Parameters

Parameters:

• from_datum – Datum transforming from

• to_datum – Datum transforming to

• ref_epoch (datetime.date) – Ref. epoch

• tx – Translation in X (m)

• ty – Translation in Y (m)

• tz – Translation in Z (m)

• sc – Scale factor (ppm)

• rx – Rotation about X (arcsec)

• ry – Rotation about Y (arcsec)

• rz – Rotation about Z (arcsec)

• d_tx – Translation rate of change in X (m/yr)

• d_ty – Translation rate of change in Y (m/yr)

• d_tz – Translation rate of change in Z (m/yr)

• d_sc – Scale factor rate of change (ppm/yr)

• d_rx – Rotate rate of change about X (arcsec/yr)

• d_ry – Rotate rate of change about Y (arcsec/yr)

• d_rz – Rotate rate of change about Z (arcsec/yr)

• tf_sd (TransformationSD) – TransformationSD object

__neg__()

Reverses the direction of the transformation object, i.e., the ITRF2014 to ITRF2000 transformation becomes the ITRF2000 to ITRF2014 transformation.

Returns:

reversed direction transformation object

__add__(other)

Change the transformation epoch to a specified date. Advances all transformation parameters by their respective rates of change.

Parameters:

other – datetime.date object

Returns:

transformation object with parameters and ref epoch moved to the specified date

class geodepy.constants.TransformationSD(sd_tx=None, sd_ty=None, sd_tz=None, sd_sc=None, sd_rx=None, sd_ry=None, sd_rz=None, sd_d_tx=None, sd_d_ty=None, sd_d_tz=None, sd_d_sc=None, sd_d_rx=None, sd_d_ry=None, sd_d_rz=None)

Transformation Standard Deviation Parameters

Parameters:

• sd_tx – one-sigma uncertainty of tx (m)

• sd_ty – one-sigma uncertainty of ty (m)

• sd_tz – one-sigma uncertainty of tz (m)

• sd_sc – one-sigma uncertainty of sc (ppm)

• sd_rx – one-sigma uncertainty of rx (arcsec/yr)

• sd_ry – one-sigma uncertainty of ry (arcsec/yr)

• sd_rz – one-sigma uncertainty of rz (arcsec/yr)

• sd_d_tx – one-sigma uncertainty of d_tx (m/yr)

• sd_d_ty – one-sigma uncertainty of d_ty (m/yr)

• sd_d_tz – one-sigma uncertainty of d_tz (m/yr)

• sd_d_sc – one-sigma uncertainty of d_sc (ppm/yr)

• sd_d_rx – one-sigma uncertainty of d_rx (arcsec/yr)

• sd_d_ry – one-sigma uncertainty of d_ry (arcsec/yr)

• sd_d_rz – one-sigma uncertainty of d_rz (arcsec/yr)

Predefined Constants

GeodePy also includes a set of predefined constants for commonly used ellipsoids, projections and transformations. These can be seen below.

Ellipsoid

For Ellipsoid:

Name	Type	Description
grs80	Ellipsoid	Geodetic Reference System 1980
wgs84	Ellipsoid	World Geodetic System 1984
ans	Ellipsoid	Australian National Spheroid
intl24	Ellipsoid	International (Hayford) 1924

Projection

For Projection:

Name	Type	Description
utm	Projection	Universal Transverse Mercator projection
isg	Projection	Integrated Survey Grid (NSW, AGD66)

Transformation

For Transformation:

Name	Type	Description
gda94_to_gda2020	Transformation	GDA94 to GDA2020 (national)
itrf2014_to_gda2020	Transformation	ITRF2014 to GDA2020
atrf2014_to_gda2020	Transformation	ATRF2014 to GDA2020
itrf2008_to_gda94	Transformation	ITRF2008 to GDA94
itrf2005_to_gda94	Transformation	ITRF2005 to GDA94
itrf2000_to_gda94	Transformation	ITRF2000 to GDA94
itrf97_to_gda94	Transformation	ITRF97 to GDA94
itrf96_to_gda94	Transformation	ITRF96 to GDA94
agd84_to_gda94	Transformation	AGD84 to GDA94
agd66_to_gda94	Transformation	AGD66 to GDA94
agd66_to_gda94_act	Transformation	AGD66 to GDA94 (ACT region)
agd66_to_gda94_tas	Transformation	AGD66 to GDA94 (Tasmania region)
agd66_to_gda94_vicnsw	Transformation	AGD66 to GDA94 (Vic/NSW region)
agd66_to_gda94_nt	Transformation	AGD66 to GDA94 (NT region)
itrf2020_to_itrf2014	Transformation	ITRF2020 to ITRF2014
itrf2020_to_itrf2014_vel	Transformation	ITRF2020 to ITRF2014 (velocity only)
itrf2020_to_itrf2008	Transformation	ITRF2020 to ITRF2008
itrf2020_to_itrf2005	Transformation	ITRF2020 to ITRF2005
itrf2020_to_itrf2000	Transformation	ITRF2020 to ITRF2000
itrf2020_to_itrf97	Transformation	ITRF2020 to ITRF97
itrf2020_to_itrf96	Transformation	ITRF2020 to ITRF96
itrf2020_to_itrf94	Transformation	ITRF2020 to ITRF94
itrf2020_to_itrf93	Transformation	ITRF2020 to ITRF93
itrf2020_to_itrf92	Transformation	ITRF2020 to ITRF92
itrf2020_to_itrf91	Transformation	ITRF2020 to ITRF91
itrf2020_to_itrf90	Transformation	ITRF2020 to ITRF90
itrf2020_to_itrf89	Transformation	ITRF2020 to ITRF89
itrf2020_to_itrf88	Transformation	ITRF2020 to ITRF88
wgs84g2296_to_itrf2020	Transformation	WGS84(G2296) to ITRF2020
wgs84g2139_to_wgs84g2296	Transformation	WGS84(G2139) to WGS84(G2296)
wgs84g1762_to_wgs84g2296	Transformation	WGS84(G1762) to WGS84(G2296)
wgs84g2139_to_itrf2014	Transformation	WGS84(G2139) to ITRF2014
wgs84g1762_to_itrf2008	Transformation	WGS84(G1762) to ITRF2008
itrf2005_to_wgs84g1674	Transformation	ITRF2005 to WGS84(G1674)
wgs84g1674_to_wgs84g1762	Transformation	WGS84(G1674) to WGS84(G1762)
wgs84g1150_to_itrf2000	Transformation	WGS84(G1150) to ITRF2000
wgs84g873_to_itrf97	Transformation	WGS84(G873) to ITRF97
wgs84g873_to_itrf96	Transformation	WGS84(G873) to ITRF96
wgs84g873_to_itrf94	Transformation	WGS84(G873) to ITRF94
wgs84g730_to_itrf91	Transformation	WGS84(G730) to ITRF91
wgs84trans_to_itrf90	Transformation	WGS84 (Transit) to ITRF90
wgs84ensemble_to_itrf2014	Transformation	WGS84 Ensemble to ITRF2014

All other combinations of ITRF transformations are available.

IERS to GeodePy Transformation

GeeodePy also includes a function for converting from IERS transfomration parameters to a GeodePy Transformation object.

geodepy.constants.iers2trans(itrf_from, itrf_to, ref_epoch, tx, ty, tz, sc, rx, ry, rz, d_tx, d_ty, d_tz, d_sc, d_rx, d_ry, d_rz, tf_sd=None)

Used to convert IERS transformation parameters into GeodePy Transformation class parameters. Note: All rotation and delta rotation terms have the sign change applied.

Parameters:

• itrf_from – ITRF realization transforming from

• itrf_to – ITRF realization transforming to

• ref_epoch – Reference epoch (YYYY.DOY)

• tx – Translation in X (mm)

• ty – Translation in Y (mm)

• tz – Translation in Z (mm)

• sc – Scale factor (ppb)

• rx – Rotation about X (milliarcsec)

• ry – Rotation about Y (milliarcsec)

• rz – Rotation about Z (milliarcsec)

• d_tx – Translation rate of change in X (mm/yr)

• d_ty – Translation rate of change in Y (mm/yr)

• d_tz – Translation rate of change in Z (mm/yr)

• d_sc – Scale factor rate of change (ppb/yr)

• d_rx – Rate of change in Rotation about X (milliarcsec/yr)

• d_ry – Rate of change in Rotation about X (milliarcsec/yr)

• d_rz – Rate of change in Rotation about X (milliarcsec/yr)

• tf_sd – TransformationSD object

Returns:

Transformation object following the Australian convention

Height

The module also contains locations for files commonly used in height converstions that will be used in the height module.