Revit Project Setup

Datum

A datum is a reference from which measurements are made. In surveying and geodesy, a datum is a set of reference points on the Earth's surface against which position measurements are made. In engineering and drafting, a datum is a reference point, surface, or axis on an object against which measurements are made.

Datums form the base of you project. Datums consists of levels, grids and references. They control the position and dimensions of your main building elements. For example: a wall is by default bound to two levels: one that determines the vertical position of the base and one for the top of the wall.

Datums play a major role behind the scenes. It emerges at various places, controlling all kinds of properties for building elements, views etc. Another great quality of using datum is to use it for parametric design. When building components are related to datums, whenever you decide to make major changes in you design, for example changing the height of the ground level, all you need to do is move the corresponding level or levels, and the entire design changes accordingly, without having to move individual elements. The fact that elements have a relation to other elements or datums and values can be specified for these relations (such as a distance) is what parametric means.

Levels and Grids are also useful as a visual reference for the designer during the design process.

There are two Panels in the Home Tab on the Ribbon: Datum and Work Plane.

Levels

Example of the use of Levels in the Villa Savoye Project

Levels are always parallel to the ground plane. They can only be created in Elevation views or Section views.

When you create a new level by sketching it, by default a corresponding Plan View is created. When you copy and existing Level, Revit won't duplicate the corresponding view. So for the first stage of setting up Levels, it's recommended to use sketching mode.

In most cases using (pick lines) and the Offset in the Option Bar is a convenient way of setting up your levels.

The main properties of levels are their name and their elevation. These properties are shown next to the Level Tag (symbol) as shown in the example above, but can also be found in the Properties Palette when a level is selected. You may change these values by clicking them or in the Properties Palette.

Use the checkboxes to display or hide the bubble at either side of the level. Use the open circles to change the length of the level line.

The 3D/2D toggle determines the effect of changes you make to the graphic extent of the level, being the length of the line and display of bubbles:

3D

changes have a project-wide effect (in all views)

2D

changes are only applied to the display of the gridline in the current view.

Any changes to the elevation of the level are always applied across the entire project.

Grids

Example of the use of Gridlines in the Villa Savoye Project

Grids are always perpendicular to levels and thus the ground plane, i.e: they are oriented vertically. Gridlines can be created in plan views as well in elevation or section views.

When in elevation or section, only grids that are perpendicular to the view direction are visible. So grids that are diagonally oriented in plan view, won't show up in elevation or section views, unless that specific view is exactly perpendicular to it.

Grids can either be straight lines (or planes actually), or arcs, as the example below shows:

The image below shows a typical Grid tag in Revit:

Use the checkboxes to display or hide the bubble at either side of the gridline. Use the open circles to change the length of the gridline.

The 3D/2D toggle determines the effect of changes you make to the graphic extent of the gridline, being the length of the line and display of bubbles:

3D

changes have a project-wide effect (in all views)

2D

changes are only applied to the display of the gridline in the current view.

Any changes to the position of the gridline (perpendicular to its direction) are always applied across the entire project.

References

Levels are always horizontal planes and Grids must always be perpendicular to the levels (vertical). In some cases you may want to use datum planes that do not have these restrictions. This is where Reference Planes come in. Reference planes can have any orientation. Don't forget to set a name for it when you create a reference plane. This makes working with reference planes a lot easier.

Reference planes can also be used to orient the work plane of a view. Use the Set icon in the Work Plane Panel of the Ribbon to change the Work Plane.