Array orientation is an important input to any PV performance model calculation.  Array orientation is usually described as either fixed tilt or tracked.

A fixed tilt orientation is one that does not move.

A tracked array’s orientation changes with time as the tracker moves the array in an attempt to reduce the angle of incidence between the sun and the array.  There are a number of different types of trackers, which are defined by how they move.

Array orientation is described by vectors of the array tilt angle ($\theta_{T}$ ) and the array azimuth angle ($\theta_{A,array}$) for each time interval in the calculation.