cedalion.geometry.ellipsoid

Ellipsoid head model for estimating landmark positions from head measurements.

Functions

get_landmarks_for_headsize(circumference, ...)

Estimate 10-20 landmark positions for a given head size on an ellipsoidal model.
cedalion.geometry.ellipsoid.get_landmarks_for_headsize(
circumference: Annotated[Quantity, '[length]'],
nz_cz_iz: Annotated[Quantity, '[length]'],
lpa_cz_rpa: Annotated[Quantity, '[length]'],
) → Annotated[DataArray, DataArraySchema(dims='label', coords='label', 'label', 'type')][source]

Estimate 10-20 landmark positions for a given head size on an ellipsoidal model.

Fits a tri-axial ellipsoid whose arc lengths match the provided head circumference and two arc measurements, then returns the positions of Cz, LPA, RPA, Nz, and Iz in the fitted ellipsoid coordinate system.

Parameters:

  • circumference – Head circumference (e.g. 560 mm).

  • nz_cz_iz – Arc length from Nz to Iz passing through Cz (anterior–posterior arc, scaled by 1.2/2 internally to match the 10-20 convention).

  • lpa_cz_rpa – Arc length from LPA to RPA passing through Cz (lateral arc, scaled by 1.2/2 internally).

Returns:

LabeledPoints with five landmarks (Cz, LPA, RPA, Nz, Iz) in the "ellipsoid" CRS, with units of mm.