Setting up a Reference Datum

For an element to be used as a reference datum, it must have:

• An origin.

• An SKEY attribute, or a parent with an SKEY attribute.

The elements you can set up as reference datums are:

• Datums;

• Equipment;

• Equipment and structural primitives such as boxes;

• Sections;

• Piping components;

• Point elements, if they have a parent with an SKEY attribute.

SKEY Attributes

Elements used to define reference datums must have an SKEY attribute, or a parent with an SKEY attribute (but note that the parent element need not be the immediate owner of the element). If the element does not have an SKEY, and no parent has an SKEY, miscellaneous SKEY types (see below) will be used.

Elements with SKEY attributes are:

• Datums

• Equipment

• Pipes

• Structures

• Substructures

• Drawings

• Frameworks

• Subframeworks

Different SKEY types have different ATEXTs associated with them, as shown in the following table.

In SKEY Types above, the symbol * represents any character. In Default texts, $ is replaced by a new line and ? is replaced by the name of the element. If the element does not have a name, Isodraft looks up the hierarchy until it finds a parent with a name, and then uses that parent’s name.

If the reference element is a Datum element, it will have an STEXT attribute. You can set this attribute to any identification text you want. If you do this, the text you enter will be used instead of the name. If you leave STEXT unset, the Datum name will be used.

You should set the SKEY text to the SKEY type you require. Note that you can also redefine the text in the ATEXT element using the ATEXT command.

Example

Pipe PIPE7-1 has an SKEY type VSTC. Associated with the pipe is ATEXT 464, with default text CL PIPELINE $?. The following text will appear on the isometric (see the example image below):

CL PIPELINE

PIPE7-1

The following image also shows a reference to a Datum, which has its STEXT element set to Zero Elevation.

Origins and Centerlines

On the isometric, a centerline is drawn through the origin of the reference element. The reference dimension will be drawn from the centerline of the reference element.

The centerline will normally be the Z-direction of the element, as defined by its orientation.

• For Piping components the p-leave will be used.

• For Sections the p-line direction will be used.

• For Points, the direction of the centerline will be to the next Point in the list. For the last Point in the list, the direction from the previous Point will be used. If there are no other Points, the direction will be the Z-direction of the Point’s owner.