How to Display Elevation Values Relative to Sea Level (ArchiCAD Insights Tutorial)

29 Feb, 2008 By: Laszlo Nagy

ArchiCAD's Reference Levels feature can create level dimensions and elevation dimensions that show values relative to sea level.

You may want to show elevations relative to sea level in certain projects. For example, you might want to show heights relative to sea level in the terrain surrounding a building, or you might want to show the elevation of certain building elements relative to sea level. ArchiCAD has the Reference Levels feature to create level dimensions (in floor plan views) and elevation dimensions (in sections/elevations) that show values relative to sea level.

Using the Gravity feature allows you to easily achieve these results. When you create dimensions on the surface of slabs, roofs, or meshes, the marker will display the actual level of those elements. More important, it will remain associated to these elements, so when their elevation values change, the level dimensions will continue to display the correct values.

For general information on these features, search the ArchiCAD Help menu or the ArchiCAD Wiki Web site for reference levels, elevation dimensions, and Gravity.

Displaying Level Dimensions Relative to Sea Level
Using the following mesh as an example, I want to display the elevations of points on its surface relative to sea level.

Imported site contours.

First I will rename one of the two additional available reference levels to sea level by selecting Options / Project Preferences / Working Units & Levels. In the Reference Levels field at the bottom of the dialog box, select 1st Reference Level by clicking on it. Modify its name to Sea Level. Select its elevation value and enter its level relative to the +/-0,0000 level of your project. For example, if the +/-0,0000 level of your project is at the height of +110,5000 meters above sea level, you would enter -110,5000 for value in this field.

Sea Level reference level.

The Sea Level reference level will move to the lowest position, since its elevation value is the lowest. Click OK.

On the floor plan, make sure that your Coordinate Box is visible, because the z height values are displayed there. If it is not displayed, you can turn it on with the Window / Palettes / Coordinates command.

Click the small right arrow in the lower right corner of the Coordinate Box to select your reference level, and select Sea Level from the list. Notice that the value has changed to Sea Level after you changed it in Project Preferences.

Coordinate Box reference level

Values in the z coordinate field will now be displayed relative to the value defined for the sea level field.

Suppose you want to show some terrain level values relative to sea level. Select the Wall tool and click the Gravitate to Mesh option of the Gravity button in the standard toolbar. Alternatively, you can turn on this option in the Coordinate Box.

Gravitate to Mesh command.

Note: The reason you need to use the Wall tool is because the Gravity option is enabled only when the active tool creates an element that can gravitate (e.g., a wall can gravitate, but a roof cannot).

Place the level dimensions over the mesh. They will display the values of the surface of the mesh. With the Level Dimension tool still active, select all level dimensions, or you can select only those level dimensions whose values you wish to show relative to sea level.

Now, with Shift-click, add one dimension text to the selection. Now you can change the settings of the dimension texts of all selected level dimension, not the settings of the level dimensions themselves.

Level dimensions on site.

Go to Dimension Text Settings. As you can see, 33 dimension texts are selected and editable. (See also Move or Edit Dimension Text in ArchiCAD Help.)

Click the AutoText radio button, and from the drop-down list to its right, select the To Sea Level option. (Do not select the Sea Level option.)

Dimension text settings.

The Text Editing field below the AutoText radio button will show the AutoText code for the option you selected. The noneditable text field below it shows a preview of what will be displayed. Click OK to accept changes. All your selected level dimensions now display values relative to your defined sea level.

Note: In the text editing field below the AutoText radio button, you can enter additional Text, which will be displayed as typed. For example, you can select the four corner Level Dimensions and type to Sea into the field.

Now you should see the following:

Dimensions relative to sea level.

Displaying Elevation Dimensions Relative to Sea Level
Like level dimensions, elevation dimensions can display values relative to sea level. You will find using the elevation dimensions even easier because the Settings dialog box contains a built-in option for sea level display. In a section/elevation view, select the elevation dimension chain you wish to modify, and go to the Elevation Dimension Settings dialog box. In the Dimension Origin drop-down list, select the Sea Level option.

Dimension selection settings.

Click the OK button to apply the change. Every Dimension Point of the Elevation Dimension Chain now displays the elevation relative to Sea Level.

Keep in mind that it is a good idea to assign a new pen to changed dimension texts so that you can distinguish custom values from default values later on. You can also select individual dimension text items of the dimension chain if you want only those items to display the sea level values. In that case, you need to use Auto Text in the Dimension Text Settings as with level dimensions.

As you explore your work process in the Virtual Building modeling tool, I expect you will find many uses for this functionality and discover you can communicate information faster and more effectively.

About the Author: Laszlo Nagy

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