My first post here. I'm designing a map at 500.000 for Italy and with EPSG 3035 or 3034 (Lambert Conical Conformal) I'm still deciding... anyway... In my map I've several points whose symbol is a sort of "rose of winds" and I need they will remain aligned with the Grid North. How could I do that? I think I'd have to calculate the angle between the Grid North and True North so I could put its value in a column that Qgis can read as an angle of rotation.
I tried with the formula
γ = arctan [tan (λ - λ0) × sin φ]
but I think there's something wrong coause the symbol doesn't align with the grid.