External References (XREFs)

This tech tip explains the guidelines for using XREFS in your drawing.

XREF is short for 'external reference' - meaning a reference to an external drawing file. The XREF is similar to a block, except the contents of the XREF 'block' are in a drawing file on disk. For the purposes of this tech tip, the drawing which you are adding the XREFS to will be called the 'master' drawing.

Your master drawing can use multiple XREFs to display the contents of external drawings inside the master drawing. This is useful to:

• Minimize the file sizes of your drawings
• Allow many users to work on individual components of a project (other users can be editing the XREF drawings while you are working on the 'master' drawing)
• Ensure that the the most recent version of the drawing is displayed every time an XREF is loaded
• Allow for easy updating, adding or removal from the main drawing at any time
• Allow for project collaboration from anywhere in the world in real time.

Guidelines for using XREFS

Correctly preparing your XREF drawings will help you to get the most out of XREFS and avoid unecessary problems.

1. If possible, remove all layouts from the XREF drawing (only the 'drawing' layout (modelspace) will be displayed in the master drawing).
2. Remove all geometry lines and geometry circles from the XREF drawing.
3. If possible, make sure drawing settings (coordinate system, scale and units) are the same as those in the master drawing.
4. If the XREF drawing has other XREFs imbedded in it, then remove them or 'bind' them into the XREF drawing.
5. Try to avoid 'circular references' which is where an XREF drawing contains an XREF which (directly or indirectly) contains a reference back to your master drawing.
6. Make sure you purge all unused styles and entities in the XREF drawing (to speed up XREF loading).
7. Save the updated XREF drawing.

Drawings can use either the Surveyor or Cartesian Coordinate System. The following explains how XREFS work in both these coordinate systems.


Adding An XREF to a Survey Drawing

Open a survey drawing by going to File Menu > Open, then browse to the folder where your survey drawing is saved, and click on the drawing file to open it. A survey drawing will be positioned at a specific geographical location:

To add an XREF to your survey drawing, go to Tools Menu > XREF Manager. The External Drawing References dialog will appear.

Click on the Add button, and browse to the folder where your survey XREF drawing is saved to, select the survey drawing (.DR4), and click Open.

The XREF will load, and an XREF INSERT should be automatically inserted into the current drawing, and you should get a message as shown below:

Click on OK. You can add another XREF by repeating steps mentioned above. The External Drawing References dialog box should be updated and list the XREFS you added:

Click on Close when you are done.

Now that you have added an XREF, there are more options for you in External Drawing References dialog:

Working with XREFS is usually quite straightforward, but there are some things to keep in mind:

1. The insertion point is very important. Everyone on a project must be working on the same set of coordinates and insert points.
2. When you Add or Load an XREF, the layers, blocks and styles in the XREF drawing will be inserted into the current drawing:
   • AllyCAD will prefix the XREF layer/blocks/styles names in the current drawing with the filename of the XREF drawing.
   • The XREF layer/blocks/styles will not be editable in the current drawing. However you can temporarily set some XREF layer properties (which will be lost if you unload/reload the XREF).
   • You may not delete XREF layers/blocks/styles.
   • All XREF layers/blocks/styles will disappear when the XREF is removed.
3. If an XREF file is moved from the location where AllyCAD expects to find it, you can update the file path to an existing XREF without having to re-add the XREF.

Adding An XREF to a Cartesian Drawing

Open the cartesian drawing by going to File Menu > Open, then browse to the folder where drawing is saved, and double-click on the drawing file to open it.

To add an XREF, go to Tools Menu > XREF Manager. The External Drawing References dialog will appear.

Click on Add, and browse to the folder where cartesian XREF drawing is saved, click on it and Open.

The XREF is added to the drawing, but no XREF INSERT is automatically inserted into the drawing (XREFS in Cartesian drawings must be inserted manually).

Click the Close button to exit the External Drawing References dialog.

XREF layers will be visible in the Layer Settings dialog:

To manually insert an XREF INSERT into your drawing, go to Insert Menu > External References. This is similar to inserting a block insert in your drawing.

AllyCAD will prompt you to indicate XREF insertion point. If you have more than one XREF, select the one you want from the dropdown in the CAD bar. You also have options to change the angle and scaling of the XREF INSERT. Click on the Tick button then indicate the XREF insertion point on the drawing:

Multiple XREF INSERTS which use the same XREF can be inserted in the drawing (similar to the way block inserts work).