pycontrails.physics.units¶

Unit conversion support.

Functions

`degrees_to_radians`(degrees)	Convert from degrees to radians.
`dt_to_seconds`(dt[, dtype])	Convert a time delta to seconds as a float with specified `dtype` precision.
`ft_to_m`(ft)	Convert length from feet to meter.
`ft_to_pl`(h)	Convert from altitude (ft) to pressure level (hPa).
`kelvin_to_celsius`(kelvin)	Convert temperature from Kelvin to Celsius.
`knots_to_m_per_s`(knots)	Convert speed from knots to meters per second (m/s).
`latitude_distance_to_m`(distance_degrees)	Convert latitude degrees distance between two points to cartesian distances in meters.
`lbs_to_kg`(lbs)	Convert mass from pounds (lbs) to kilograms (kg).
`longitude_distance_to_m`(distance_degrees, ...)	Convert longitude degrees distance between two points to cartesian distances in meters.
`m_per_s_to_knots`(m_per_s)	Convert speed from meters per second (m/s) to knots.
`m_to_T_isa`(h)	Calculate the ambient temperature (K) for a given altitude (m).
`m_to_ft`(m)	Convert length from meters to feet.
`m_to_latitude_distance`(distance_m)	Convert cartesian distance (meters) to differences in latitude degrees.
`m_to_longitude_distance`(distance_m, ...)	Convert cartesian distance (meters) to differences in longitude degrees.
`m_to_pl`(h)	Convert from altitude (m) to pressure level (hPa).
`mach_number_to_tas`(mach_number, T)	Calculate true airspeed from the Mach number at a specified ambient temperature.
`pl_to_ft`(pl)	Convert from pressure level (hPa) to altitude (ft).
`pl_to_m`(pl)	Convert from pressure level (hPa) to altitude (m).
`radians_to_degrees`(radians)	Convert from radians to degrees.
`tas_to_mach_number`(true_airspeed, T)	Calculate Mach number from true airspeed at a specified ambient temperature.

pycontrails.physics.units.degrees_to_radians(degrees)¶

Convert from degrees to radians.

Parameters:: degrees (ArrayScalarLike) – Degrees values, [\(\deg\)]
Returns:: ArrayScalarLike – Radians values

pycontrails.physics.units.dt_to_seconds(dt, dtype=<class 'numpy.float64'>)¶

Convert a time delta to seconds as a float with specified dtype precision.

Parameters:

dt (numpy.ndarray) – Time delta for each waypoint
dtype (np.dtype) – Data type of the output array

Returns:

numpy.ndarray – Time delta in seconds as a float

pycontrails.physics.units.ft_to_m(ft)¶

Convert length from feet to meter.

Parameters:: ft (ArrayScalarLike) – length, [\(ft\)]
Returns:: ArrayScalarLike – length, [\(m\)]

pycontrails.physics.units.ft_to_pl(h)¶

Convert from altitude (ft) to pressure level (hPa).

Assumes the ICAO standard atmosphere.

Parameters:: h (ArrayScalarLike) – altitude, [\(ft\)]
Returns:: ArrayScalarLike – pressure level, [\(hPa\)], [\(mbar\)]

See also

m_to_pl, pl_to_ft, m_to_T_isa

pycontrails.physics.units.kelvin_to_celsius(kelvin)¶

Convert temperature from Kelvin to Celsius.

Parameters:: kelvin (ArrayScalarLike) – temperature [\(K\)]
Returns:: ArrayScalarLike – temperature [\(C\)]

pycontrails.physics.units.knots_to_m_per_s(knots)¶

Convert speed from knots to meters per second (m/s).

Parameters:: knots (ArrayScalarLike) – Speed, [\(knots\)]
Returns:: ArrayScalarLike – Speed, [\(m \ s^{-1}\)]

pycontrails.physics.units.latitude_distance_to_m(distance_degrees)¶

Convert latitude degrees distance between two points to cartesian distances in meters.

Parameters:: distance_degrees (ArrayScalarLike) – latitude distance, [\(\deg\)]
Returns:: ArrayScalarLike – Cartesian distance along the latitude axis, [\(m\)]

pycontrails.physics.units.lbs_to_kg(lbs)¶

Convert mass from pounds (lbs) to kilograms (kg).

Parameters:: lbs (ArrayScalarLike) – mass, pounds [\(lbs\)]
Returns:: ArrayScalarLike – mass, kilograms [\(kg\)]

pycontrails.physics.units.longitude_distance_to_m(distance_degrees, latitude_mean)¶

Convert longitude degrees distance between two points to cartesian distances in meters.

Parameters:

distance_degrees (ArrayScalarLike) – longitude distance, [\(\deg\)]
latitude_mean (ArrayScalarLike, optional) – mean latitude between longitude_1 and longitude_2, [\(\deg\)]

Returns:

ArrayScalarLike – cartesian distance along the longitude axis, [\(m\)]

pycontrails.physics.units.m_per_s_to_knots(m_per_s)¶

Convert speed from meters per second (m/s) to knots.

Parameters:: m_per_s (ArrayScalarLike) – Speed, [\(m \ s^{-1}\)]
Returns:: ArrayScalarLike – Speed, [\(knots\)]

pycontrails.physics.units.m_to_T_isa(h)¶

Calculate the ambient temperature (K) for a given altitude (m).

Assumes the ICAO standard atmosphere.

Parameters:: h (ArrayScalarLike) – altitude, [\(m\)]
Returns:: ArrayScalarLike – ICAO standard atmosphere ambient temperature, [\(K\)]

References

[Wikipedia contributors, 2023]

Notes

See https://en.wikipedia.org/wiki/International_Standard_Atmosphere

See also

m_to_pl, ft_to_pl

pycontrails.physics.units.m_to_ft(m)¶

Convert length from meters to feet.

Parameters:: m (ArrayScalarLike) – length, [\(m\)]
Returns:: ArrayScalarLike – length, [\(ft\)]

pycontrails.physics.units.m_to_latitude_distance(distance_m)¶

Convert cartesian distance (meters) to differences in latitude degrees.

Small angle approximation for distance_m << constants.radius_earth

Parameters:: distance_m (ArrayScalarLike) – cartesian distance along latitude axis, [\(m\)]
Returns:: ArrayScalarLike – latitude distance, [\(\deg\)]

pycontrails.physics.units.m_to_longitude_distance(distance_m, latitude_mean)¶

Convert cartesian distance (meters) to differences in longitude degrees.

Small angle approximation for distance_m << constants.radius_earth

Parameters:

distance_m (ArrayScalarLike) – cartesian distance along longitude axis, [\(m\)]
latitude_mean (ArrayScalarLike) – mean latitude between longitude_1 and longitude_2, [\(\deg\)]

Returns:

ArrayScalarLike – longitude distance, [\(\deg\)]

pycontrails.physics.units.m_to_pl(h)¶

Convert from altitude (m) to pressure level (hPa).

Parameters:: h (npt.NDArray[np.float64]) – altitude, [\(m\)]
Returns:: npt.NDArray[np.float64] – pressure level, [\(hPa\)], [\(mbar\)]

References

[Wikipedia contributors, 2023]

Notes

See https://en.wikipedia.org/wiki/Barometric_formula

See also

m_to_T_isa, ft_to_pl

pycontrails.physics.units.mach_number_to_tas(mach_number, T)¶

Calculate true airspeed from the Mach number at a specified ambient temperature.

Parameters:

mach_number (float | npt.NDArray[np.float64]) – Mach number, [:math: Ma]
T (npt.NDArray[np.float64]) – Ambient temperature, [\(K\)]

Returns:

npt.NDArray[np.float64] – True airspeed, [\(m \ s^{-1}\)]

References

[Cumpsty and Heyes, 2015]

pycontrails.physics.units.pl_to_ft(pl)¶

Convert from pressure level (hPa) to altitude (ft).

Assumes the ICAO standard atmosphere.

Parameters:: pl (ArrayScalarLike) – pressure level, [\(hPa\)], [\(mbar\)]
Returns:: ArrayScalarLike – altitude, [\(ft\)]

See also

pl_to_m, ft_to_pl, m_to_T_isa

pycontrails.physics.units.pl_to_m(pl)¶

Convert from pressure level (hPa) to altitude (m).

Function is slightly different from the classical formula: constants.T_msl / 0.0065) * (1 - (pl_pa / constants.p_surface) ** (1 / 5.255) in order to provide a mathematical inverse to m_to_pl().

For low altitudes (below the tropopause), this implementation closely agrees to classical formula.

Parameters:: pl (ArrayLike) – pressure level, [\(hPa\)], [\(mbar\)]
Returns:: ArrayLike – altitude, [\(m\)]

References

[Wikipedia contributors, 2023]

Notes

See https://en.wikipedia.org/wiki/Barometric_formula

See also

pl_to_ft, m_to_pl, m_to_T_isa

pycontrails.physics.units.radians_to_degrees(radians)¶

Convert from radians to degrees.

Parameters:: radians (ArrayScalarLike) – degrees values, [\(\rad\)]
Returns:: ArrayScalarLike – Radian values

pycontrails.physics.units.tas_to_mach_number(true_airspeed, T)¶

Calculate Mach number from true airspeed at a specified ambient temperature.

Parameters:

true_airspeed (ArrayScalarLike) – True airspeed, [\(m \ s^{-1}\)]
T (ArrayScalarLike) – Ambient temperature, [\(K\)]

Returns:

ArrayScalarLike – Mach number, [:math: Ma]

References

[Cumpsty and Heyes, 2015]