Base Slope

In the sheds option, you can define a slope for the basis of the sheds (useful, for example when positioning PV modules in shed arrangement perpendicularly on a tilted roof).

Then, when tilting the Base of a PV plane (or shed), both orientation parameters change. It is astonishing and not intuitive, but quite normal.

For understanding that: Please take a cardboard as PV Plane. First incline it toward south (in front of you by imagination), and then tilt the basis (according to your roof).

Now imagine a horizontal line passing through your collector plane (will be oblique with respect to your field-rectangle). The new plane orientation (azimuth) is the perpendicular to this line. It can be very far from south even with little tilt angles. And the new tilt will be the slope of the perpendicular to this line in the plane.

For a rigorous calculation you should define the normal to the plane, and apply rotation matrices. This is not straightforward.

PVsyst performs this calculation in the Near shadings part, and asks for updating the "orientation" parameters accordingly.