Hello,

It turns out, if we consider this local coordinate system strictly, then for any point of standing (except for P0) - there must be vertical deflections?

Yes, the vertical of P0 is orthogonal to the local plane (the vertical axis is the normal axis) and the vertical is orthogonal to the surface of the ellipsoid. Each point is transformed to local plane. The tilt of the vertical of such points must be taken into account during the adjustment.

Kind reagrds
Micha