Internal reference system

The internal cartesian reference system is a right-handed system with the particularity that the axes labels are unorthodox. Usually, X points to the fundamental direction, Z points up and XY is the fundamental plane, with Y pointing to the direction that makes it a right-handed system. In our case, it is Z which points to the fundamental direction, Y points up and XZ is the fundamental plane.

In order to convert from common equatorial cartesian coordinates (XYZ) to Gaia Sky coordinates (X'Y'Z'), you just need to switch the axes:

  • X' = Y
  • Y' = Z
  • Z' = X


So, in Gaia Sky XZ is the equatorial plane. Z points towards the vernal equinox point, Aries (♈) where ra=0^\circ. Y points towards the north celestial pole (dec=90^\circ). X is perpendicular to both Z and Y and points to ra=90^\circ.

Gaia Sky reference system

Gaia Sky reference system

All the positions and orientations of the entities in the scene are at some point converted to this reference system for representation. The same happens with the orientation sensor data in mobile devices.