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Why Use Datum

• Set Datum to express height and plan distance in a compact and local way, tailored to your project.
• Landshape commands will express position in relation to the model datum. For instance, Contour and Grid start at the Datum. Draw tools express height in relation to the Datum.
• The Datum makes it easy to control the point-of-departure for spatial View and Survey commands.
• The Datum makes it easy to avoid awkwardly long distance expressions.

How to Use Datum

• To show the current Datum, run :Set Datum:. This shows the current position of the datum.
• To resposition the Datum, run :Set Datum:. In the tool, then click anywhere in the model. If you wish, finetune height in VCB. To set the Datum, hit Enter or Doubleclick. To keep the previous datum, hit Escape.

An Example

Let's say that you are working on a house project in the mountains. The foundation level is positioned at 1924.12 meters above sea level.

By setting your project Datum to a corner of the groundplate, you can express heights relative to the local foundation, instead of relative to the distant sea level.

Datum Tips

• For heights, the datum works as a horizontal plane. In some projects, only Datum height matters.
• When setting your Datum, try picking a reference point which will remain fixed thoughout your project.
• The Datum is an abstract entity, which sits in a point in space in your model file. It is not fixed to any terrain plot or other pieces of geometry.
• There is always a datum in the model.
• If no datum has been set in your model, Landshape will use Sketchup's global model origin as the datum.
• There can be only one datum per model.

Read Statusbar and VCB for Details

• When Set Datum is active, Sketchup's statusbar will show the current state and options. Read the statusbar carefully.
• The VCB and its label shows any current parameters. Right after a Set Datum commit, try typing different values and hit Enter to control the Set Datum effect.
• To explore the tool, open a new sandbox model. Plot-quake a random terrain. Then try Set Datum on it. Don't be afraid to play around!