Through the dihedral method of plane change.
It consists of modifying the position of one of the two projection planes, to transform an oblique plane into a vertical or horizontal projecting plane.
It is preferable to move the vertical projection plane or P V, until the horizontal traces of the oblique planes are perpendicular to this plane.
With this, we will have modified the oblique planes in vertical projectors, or perpendicular to the vertical projection plane.
In the vertical or elevation projection, the distance between the two parallel planes will be seen, directly, in true magnitude.
We are going to make a vertical plane change.
Wherever you want, you draw a line perpendicular to one of the horizontal traces, for example, to alpha one.
Double lateral segments are drawn, indicating that it is a new Land Line.
You write v, with subscript one, because the vertical projection plane has been modified once.
From the cut-off point of the two land lines, a vertical is drawn to cut to the two alpha trace, generating the projections of a point a, on this trace.
With the compass, the elevation of this point is moved, perpendicular, now, to the new land line.
The cut-off point of alpha one, with the new land line, joins the new vertical projection to, two, premium.
Creating the new vertical projection of the alpha plane. This becoming a vertical projecting plane or perpendicular to the vertical projection plane.
The beta plane is parallel to the alpha, therefore, its projections continue to be parallel.
Let's extend the horizontal projection of the beta plane.
and at the cut-off point with the new land line, its new beta vertical trace, two, premium, is drawn in parallel.
The distance between the two parallel planes, in true magnitude is direct, in the new vertical projection created.