Preparing a DGN V8 seed file

This workflow demonstrates how to prepare a DGN V8 seed file for use with the Export To CAD tool. Exporting data to the DGN V8 format requires a seed file with the following:

Calculate the global origin

The global origin is the coordinate location x,y = 0,0 in a DGN file. To avoid the possibility of generating empty output, shift the global origin to accommodate the extents of the features to be exported. You calculate the global origin using the MIN/MAX coordinates that are viewable in the Feature Class Properties dialog box. When exporting multiple feature classes, use the smallest minimum values and the largest maximum values for your calculations, and roundoff the result.

  1. Open a Catalog window.
  2. Right click the feature class and click Properties.
  3. Click the Domain tab.
  4. Calculate the approximate center of the extents from the values in the XY Domain box, using the formula:
    Global Origin X = (MaxX + MinX) / 2
    Global Origin Y = (MaxY + MinY) / 2

Determine if the data is 2D or 3D

  1. Click the General tab in the Feature Class Properties dialog box.
  2. Confirm in the Geometry Properties box if the coordinates include z-values. A checked box indicates the feature class contains 3D data.

Using MicroStation V8 to prepare the seed file

Start an editing session

  1. Start MicroStation.
  2. Click File > New.
  3. Enter a name for the seed file in the Filename textbox.
  4. In the Seed textbox, browse to the Bentley system folder and choose an empty 2D or 3D seed file as determined by the z-values of your input feature class.
  5. Click Save to begin editing the new DGN file.

A typical Windows installation will locate the folder at C:\Documents and Settings\All Users\Application Data\Bentley\Workspace\system\seed.

Set the map units

  1. Click Settings > Design File.
  2. Click Working Units from the Category menu.
  3. Click Edit in the Advanced Settings box to open the Advanced Unit Settings dialog box.

    Click OK to dismiss any warning you receive about modifying existing entities.

  4. In the Resolution box, enter a nominal value that defines the precision required for your data, choose a unit of measure from the drop-down arrow, and click OK.
  5. A larger resolution setting creates a smaller design cube/plane with greater precision. Conversely, a smaller number provides less precision but a larger design cube/plane.
  6. Click OK to close the DGN File Settings dialog box.

Define the global origin

  1. Click Utilities > Key-in.
  2. Type GO=<Global Origin X>,<Global Origin Y> in the text box, using the x,y coordinates you calculated as the center of the input feature class.

    For example: GO=1000,1000

  3. Press ENTER and close the dialog box.

Once entered, the GO= parameter cannot be undone. One method to recover from an incorrect key-in is to close the file without saving the settings, and reopen it.

Save and close the DGN file

  1. From the menu toolbar, click File > Save Settings or press CTRL+F to save the settings.
  2. From the menu toolbar, click File > Save or press CTRL+S to save the file.

Related Topics

Published 6/8/2010