A Pitch Circle Dimension (PDIM) is a form of radial dimension, which may be used to draw radius, and diameter dimensions between two independently definable points. A PDIM is defined by two Dimension Point elements that are owned by the PDIM. These in turn are defined by p-points/p-lines (Radial Dimension P-Point, RPPT element) or 3D positions (Radial Dimension Position Point, RPOI element). As with Linear Dimension Points, it is possible to use a RULE to parameterise 3D positions. It is not possible to create more than two Radial Dimension Points. A PDIM will be drawn when two significant dimension points are defined. It is not normally necessary to navigate to the two individual Dimension Points.

The first dimension point will be at the centre of the dimension, the second will define the circumference of the dimension. A PDIM contains the same style attributes as an RDIM (refer to Appearance of Radial Dimensions - Specific Attributes for further information), but does not have DDNM/DDNX and AKEY attributes. As with RDIMs, the meaning of the ’#DIM’ dimension text is defined by the DFLAG attribute. The dimension points contain no style attributes. Figure 11:30.: Pitch Circle Dimension - example shows a simple example PDIM (bold line - other dimensions are RDIMs).

The dimension radius will be the distance between the two dimension points as projected into the VIEW, not the true 3D distance between these points. This projected distance defines the value reported in the dimension text. This is consistent with the functionality for Linear Dimensions (LDIMs) with Direction TRUE (refer to Principal Attributes of Linear Dimensions for further information).