References to Frame and Longitudinal Positions

References to principal planes in the ship can be done using the following options:

• define the position along the x-axis relative to frame locations ("frame terms").

• define positions along the y- and z-axes, respectively, by reference to theoretical longitudinal positions in the midship section (LP-terms from Longitudinal Position).

  The positions referred to are those defined in input to the GENTAB program (SF406D) , see the documentation for further information.

  <plane_ref>:= <FR-term> | <LP-term>

  <FR-term> and <LP-term> have the same syntactical construct, below described for the <FR-term>.

  <FR-term>::= FR<start> [([<step>]) <end> ][ +|- <dist> ]
  

  <start>::= <step>::= <end>::= <dist>::= <number>

If step is given, it is calculated in the same way as in <rep_term>.

If the number is not an integer in an FR/LP-term, the position will be interpolated between the two closest frame/longitudinal positions.

A negative longitudinal number means that the negative longitudinal coordinate will be evaluated (only for positions along the y-axis).

<dist> is the offset, relative to the frame/longitudinal positions.

FR-terms can be used only to define positions along the x-axis. LP-terms define positions along the y-axis for numbers of bottom longitudinals, positions along the z-axis for numbers of side longitudinals.

Additionally, FR-terms may be used for u-coordinates if the u-axis coincides with the x-axis. LP-terms may be used for u- and v-coordinates if the corresponding axis coincides with the axis for which LP-terms is relevant.

Violation of these rules will produce incorrect results without any error signals.