# RTN Transformations

Rotation matrices between ECI (Earth-Centered Inertial) and RTN (Radial-Tangential-Normal) orbital frames.

**note**
For conceptual explanations of the RTN frame, see [Relative Motion](../../learn/relative_motion/index.md).

::: brahe.rotation_rtn_to_eci

::: brahe.rotation_eci_to_rtn

::: brahe.state_rtn_to_eci

::: brahe.state_eci_to_rtn