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Geodetic and Geocentric Coordinates

Functions for converting between geodetic, geocentric, and ECEF coordinates.

Geodetic Conversions

position_geodetic_to_ecef builtin 

position_geodetic_to_ecef(x_geod: Union[ndarray, List], angle_format: AngleFormat) -> ndarray

Convert geodetic position to ECEF Cartesian coordinates.

Transforms a position from geodetic coordinates (longitude, latitude, altitude) using the WGS84 ellipsoid model to Earth-Centered Earth-Fixed (ECEF) Cartesian coordinates.

Parameters:

Name Type Description Default
x_geod ndarray or list

Geodetic position [longitude, latitude, altitude] where longitude is in radians or degrees, latitude is in radians or degrees, and altitude is in meters above the WGS84 ellipsoid.

 required
angle_format AngleFormat

Angle format for input angular coordinates (RADIANS or DEGREES).

 required

Returns:

Type Description
ndarray

numpy.ndarray: ECEF Cartesian position [x, y, z] in meters.
Example 
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import brahe as bh
import numpy as np

# Convert geodetic coordinates (GPS-like) to ECEF
lon, lat, alt = -105.0, 40.0, 1655.0  # Boulder, CO (degrees, meters)
x_geod = np.array([lon, lat, alt])
x_ecef = bh.position_geodetic_to_ecef(x_geod, bh.AngleFormat.DEGREES)
print(f"ECEF position: {x_ecef}")

position_ecef_to_geodetic builtin 

position_ecef_to_geodetic(x_ecef: Union[ndarray, List], angle_format: AngleFormat) -> ndarray

Convert ECEF Cartesian position to geodetic coordinates.

Transforms a position from Earth-Centered Earth-Fixed (ECEF) Cartesian coordinates to geodetic coordinates (longitude, latitude, altitude) using the WGS84 ellipsoid model.

Parameters:

Name Type Description Default
x_ecef ndarray or list

ECEF Cartesian position [x, y, z] in meters.

 required
angle_format AngleFormat

Angle format for output angular coordinates (RADIANS or DEGREES).

 required

Returns:

Type Description
ndarray

numpy.ndarray: Geodetic position [longitude, latitude, altitude] where longitude is in radians or degrees, latitude is in radians or degrees, and altitude is in meters above the WGS84 ellipsoid.
Example 
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import brahe as bh
import numpy as np

# Convert ECEF to geodetic coordinates (GPS-like)
x_ecef = np.array([-1275936.0, -4797210.0, 4020109.0])  # Example location
x_geod = bh.position_ecef_to_geodetic(x_ecef, bh.AngleFormat.DEGREES)
print(f"Geodetic: lon={x_geod[0]:.4f}°, lat={x_geod[1]:.4f}°, alt={x_geod[2]:.0f}m")

Geocentric Conversions

position_geocentric_to_ecef builtin 

position_geocentric_to_ecef(x_geoc: Union[ndarray, List], angle_format: AngleFormat) -> ndarray

Convert geocentric position to ECEF Cartesian coordinates.

Transforms a position from geocentric spherical coordinates (longitude, latitude, radius) to Earth-Centered Earth-Fixed (ECEF) Cartesian coordinates.

Parameters:

Name Type Description Default
x_geoc ndarray or list

Geocentric position [longitude, latitude, radius] where longitude is in radians or degrees, latitude is in radians or degrees, and radius is in meters.

 required
angle_format AngleFormat

Angle format for input angular coordinates (RADIANS or DEGREES).

 required

Returns:

Type Description
ndarray

numpy.ndarray: ECEF Cartesian position [x, y, z] in meters.
Example 
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import brahe as bh
import numpy as np

# Convert geocentric coordinates to ECEF
lon, lat, r = 0.0, 0.0, 6378137.0  # Equator, prime meridian, Earth's radius
x_geoc = np.array([lon, lat, r])
x_ecef = bh.position_geocentric_to_ecef(x_geoc, bh.AngleFormat.RADIANS)
print(f"ECEF position: {x_ecef}")

position_ecef_to_geocentric builtin 

position_ecef_to_geocentric(x_ecef: Union[ndarray, List], angle_format: AngleFormat) -> ndarray

Convert ECEF Cartesian position to geocentric coordinates.

Transforms a position from Earth-Centered Earth-Fixed (ECEF) Cartesian coordinates to geocentric spherical coordinates (longitude, latitude, radius).

Parameters:

Name Type Description Default
x_ecef ndarray or list

ECEF Cartesian position [x, y, z] in meters.

 required
angle_format AngleFormat

Angle format for output angular coordinates (RADIANS or DEGREES).

 required

Returns:

Type Description
ndarray

numpy.ndarray: Geocentric position [longitude, latitude, radius] where longitude is in radians or degrees, latitude is in radians or degrees, and radius is in meters.
Example 
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import brahe as bh
import numpy as np

# Convert ECEF to geocentric coordinates
x_ecef = np.array([6378137.0, 0.0, 0.0])  # Point on equator, prime meridian
x_geoc = bh.position_ecef_to_geocentric(x_ecef, bh.AngleFormat.DEGREES)
print(f"Geocentric: lon={x_geoc[0]:.2f}°, lat={x_geoc[1]:.2f}°, r={x_geoc[2]:.0f}m")