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Corrections

Corrections to a gravity signal

Sign of corrections

All corrections have to be subtracted from the measured gravity value.

EOP_PATH = Path.home() / '.config' / 'gravitools' / 'finals2000A.all.csv' module-attribute

Default path where EOP data is saved

EOP_URL = 'https://datacenter.iers.org/data/csv/finals2000A.all.csv' module-attribute

Default URL to EOP data

STANDARD_ADMITTANCE = -3 module-attribute

Standard pressure admittance factor, in nm/s² per hPa

eop_data = None module-attribute

Earth orientation parameter data

This is set automatically by read_eop_data().

dg_polar(timeindex, lat, lon, eop=None)

Polar motion correction for a time series.

Parameters:

Name Type Description Default
timeindex DatetimeIndex

Time index (UTC) for which to calculate the correction.

 required
lat float

Latitude, in degree.

 required
lon float

Longitude, in degree.

 required
eop DataFrame

Time series of polar motion coordinates.

 None

Returns:

Type Description
Series

Time series of polar motion correction, in nm/s².

effective_tilt(tilt_x, tilt_y)

Effective tilt angle, from X and Y angles

getEOPdata_postInstall()

Download EOP data for first usage, directly after package installation

get_eop_data()

Read the EOP data from file, if it is not yet available

nominal_pressure(altitude)

Nominal pressure at given altitude.

Parameters:

Name Type Description Default
altitude float

Location altitude, in meters.

 required

Returns:

Type Description
float

Nominal pressure, in hPa.

polar_motion_correction(pol_x, pol_y, lat, lon)

Gravity correction due to polar motion.

Reference: IAGBN Absolute Gravity Observations Documentation for BGI-Files (1992).

Parameters:

Name Type Description Default
pol_x float

Polar motion X angle coorinate, in arcsec.

 required
pol_y float

Polar motion Y angle coorinate, in arcsec.

 required
lat float

Latitude of measurement site, in degree.

 required
lon float

Longitude of measurement site, in degree.

 required

Returns:

Type Description
float

Gravity correction, in nm/s².

pressure_correction(p_atm, altitude, admittance=STANDARD_ADMITTANCE)

Gravity correction due to atmospheric pressure.

Parameters:

Name Type Description Default
p_atm float | Series | ndarray

Atmospheric pressure values, in hPa.

 required
altitude float

Location altitude, in meters.

 required
admittance float

Pressure admittance factor, in nm/s^2 per hPa.

 STANDARD_ADMITTANCE

Returns:

Type Description
float | Series | ndarray

Gravity correction, in nm/s².

read_eop_data(path=None)

Read EOP data from file

tilt_correction(g_raw, tilt_x, tilt_y)

Instrument tilt gravity correction.

Note that tilt_x and tilt_y are cast to float64, because float32 is insufficient precision.

Parameters:

Name Type Description Default
g_raw float

Measured gravity value, in nm/s².

 required
tilt_x float

Instrument tilt angle in X direction, in rad.

 required
tilt_y float

Instrument tilt angle in Y direction, in rad.

 required

Returns:

Type Description
float

Gravity correction, in nm/s².

update_eop_data(expire='12h')

Request the EOP data file, if necessary