Orientation convention

Convention for Angle Origins

In-Plane Orientation ($\rho$)

The orientation angle $\rho$ (used for sticks and histograms) is calculated counter-clockwise within the field of view. The following image defines the origin and the direction of increase. Note the specific pixel numbering convention used for the horizontal ($x$) and vertical ($y$) axes.

Out-of-Plane Orientation ($\eta$)

For 4POLAR methods, the orientation angle $\eta$ is defined relative to the imaging depth:

• $0^\circ$: The transition dipole is perpendicular to the image plane.
• $90^\circ$: The transition dipole is parallel to the image plane.