In this first article on ship lenghts, I will begin by referring to the plans and reference lines of the ship. I will also distinguish the total length (LOA) and the length between perpendiculars (LPP).

Ship views

Base view:

It’s the view that looks like it’s seen from above.

Longitudinal view:

it’s the ship’s side view



Transverse view:

It’s the plane of the ship in which we see a slice of the ship, as if cut off from the front.



Reference lines


Construction Line or Keel:

It’s the line formed by the intersection of the longitudinal plane with the keel.

Base line:

It’s the line formed by the intersection of the base plane with the longitudinal plane of the ship. This is the reference line of the ship’s geometric plane.

Floating line or water line:

It’s the line defined by the intersection of the flotation plane and the hull of the ship.

Design waterline (DWL):

It’s the waterline when the ship is at it’s maximum level of load (calculated when the ship is designed).

Perpendicular forward:

It’s the line perpendicular to the baseline, which passes at the end of the intersection of the water line when the ship is loaded at the maximum of its load

Perpendicular aft:

It’s the straight line perpendicular to the base line, which passes through the rudder axis.

Perpendicular midship:

The straight line perpendicular to the baseline, which is equidistant from both forward and aft perpendiculars.

Ship lenghts

Length between perpendiculars (LPP):

It’s the distance measured parallel to the waterline (DWL) between the forward and aft perpendiculars. This length is important as it is used for ship stability calculations.

Lenght Overall (LOA):

It’s the lenght between the beginning of the bow to the end of the stern.


Hope you liked it! 😉

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