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RFEM – Online Manual

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11.3.4 Coordinate Systems

Coordinate Systems

User-defined coordinate systems make entering inclined parts of a model easier. They have nothing to do with the axis systems of lines, surfaces, or members. Alternatively, you can define work planes graphically by means of points, line axes, member axes, or surface axes (see Chapter 11.3.1).

To open the Coordinate System dialog box, select the menu item

    • Tools → Coordinate System

or use the toolbar button shown on the left.

Figure 11.47 Coordinate System button

You can also use the button in the Work Plane and Grid/Snap dialog box (see Figure 11.34) to create a user-defined coordinate system.

Figure 11.48 Coordinate System dialog box

The Standard coordinate system related to the global axes XYZ and the origin is preset.

Creating a new coordinate system

Click the button shown in Figure 11.48 to open the following dialog box. You can find the same button in the Work Plane and Grid/Snap dialog box (see Figure 11.34).

Figure 11.49 Define New Coordinate System dialog box

Enter a Name for the new coordinate system. Then, define the axis system with the help of three parameters in the UVW Coordinate System Related to XYZ CS dialog section:

    • Origin (zero point of new coordinate system)
    • Point on positive U-axis (first axis)
    • Point in positive UW-plane (rotation of plane about axis U)

For this purpose, specify three points that you can enter directly or select graphically. The points must not lie on a straight line.

You can use the buttons shown on the left to select the three [Nodes] or [Points] one after the other in the work window (please observe the sequence when defining points 0 to 2). With the left button, you can only select Nodes; with the right button, you can select any Points. The difference becomes especially significant when a node that represents a definition point of the coordinate system is changed. The coordinate system is then adjusted automatically. In case of arbitrary points, the system of coordinates is fixed.

If a user-defined work plane is defined with the help of three points (see Chapter 11.3.1), RFEM automatically creates a new coordinate system with the name Generated.

Editing or deleting coordinate systems

Only user-defined coordinate systems can be edited or deleted. For this purpose, there are two available buttons in the Coordinate System dialog box.

Table 11.4 Buttons in the Coordinate System dialog box

Modifies selected coordinate system.

Deletes selected coordinate system.


In a frame joint, a new coordinate system is defined for the diagonal that lies in the plane of the roof. The Origin is set in corner node 6. End node 4 of the diagonal member is selected as a Point on positive U-Axis and base node 5 of the column as a Point in positive UW-Plane.

Figure 11.50 User-defined coordinate system UVW in a frame joint

The grid then refers to the work planes UV, VW, and UW where you can define new objects (see Chapter 11.3.1).