# GCRF ↔ ITRF Transformations

Transformations between Geocentric Celestial Reference Frame (GCRF, inertial) and International Terrestrial Reference Frame (ITRF, Earth-fixed). Uses IAU 2006/2000A CIO-based theory with classical angles.

**note**
For conceptual explanations and examples, see [GCRF ↔ ITRF Transformations](../../learn/frames/gcrf_itrf.md) in the Learn section.

## GCRF to ITRF

::: brahe.state_gcrf_to_itrf

::: brahe.rotation_gcrf_to_itrf

::: brahe.position_gcrf_to_itrf

## ITRF to GCRF

::: brahe.state_itrf_to_gcrf

::: brahe.rotation_itrf_to_gcrf

::: brahe.position_itrf_to_gcrf

## Intermediate Matrices

::: brahe.bias_precession_nutation

::: brahe.earth_rotation

::: brahe.polar_motion

## See Also

- [ECI ↔ ECEF Transformations](eci_ecef.md) - Generic naming convention API
- [Reference Frames Module](index.md) - Complete API reference for frames module