How To: Create a Microstation seed file for use with the Export to CAD geoprocessing tool
Instructions provided describe how to create a Microstation seed file for use with the Export to CAD geoprocessing tool. The Export to CAD geoprocessing tool creates Microstation design files from ArcGIS feature layers and a required Microstation seed file. A seed file is essentially a blank Microstation design file with the appropriate settings. Microstation seed files define the design plane, including appropriate dimensions, units, and origin.
A seed file must contain any line's style definitions and shared cell definitions referenced by the Export to CAD tool, unless appended to an existing Microstation file that already contains these definitions and settings.
If the design plane of the seed file does not fit well with the selected feature classes, many problems may occur, including objects that are created but are not visible.
All Microstation files must be designated as either 2D or 3D files. By default, the Export to CAD tool provides a sample Microstation 3D seed file. A sample 2D seed file is also available for selection for 2D files. It is unlikely that these default seed files are optimal for the design file to be created. Using a Microstation seed file that fits the data is strongly suggested.
The fastest and easiest way to create a seed file is from an existing Microstation design file with the appropriate settings. In Microstation, copy the file to a new name and delete all the elements out of it.
If a valid Microstation seed file that fits the data is currently present, use that file repeatedly. There is no need to create a new one.
Create a new seed file from scratch by following the steps below.
The following procedures require use of version 8 or higher of Bentley’s Microstation CAD software. ArcGIS 9.0 or higher is also required.
- Determine if the data is 3D or 2D using ArcCatalog. Right-click on a feature class to export to a Microstation file. Navigate to the Properties > Fields Tab and click on the [Shape] field in the field name column of the dialog box. If the feature class contains Z Values, create a 3D Microstation seed file. Otherwise, use a 2D seed file.
- Calculate an acceptable value for the Microstation Global Origin by recording values from the Properties > Fields Tab > Shape field of each feature class.
Click on the ellipses button at the bottom of the dialog box, next to the 'Spatial Reference' field property, and click on the 'X/Y Domain' tab.
Calculate an approximate center point using the following formula, and using the MIN/MAX coordinates of each feature class:
Global Origin X = (MaxX + MinX) / 2
Global Origin Y = (MaxY + MinY) / 2
If multiple feature classes are present, record the smallest Min values and the largest Max values for calculating the Microstation Global Origin point. Round off the result to nominal values.
- Open Microstation V8 to create the 2D or 3D Microstation seed file.
- Select File > New from the Microstation main file menu.
- Enter or navigate to a base seed file on the bottom of the dialog box. Use either of the Bentley-provided default seed files, seed2d.dgn or seed3d.dgn, found in the ..Bentley\Workspace\System\seed\ directory. The file selected depends on if a 2D or a 3D design file is required.
- Type in a name for the new seed file and click OK to open the Microstation editing environment.
- Set the working units of the new seed file by selecting the Settings > Design File option from the drop-down menu.
- Select the appropriate unit names. Click the 'Advanced' button.
- Click OK, when the warning about modifying existing entities appears.
- Fill in the 'Resolution' value with a nominal value that defines essentially the precision of the data. The larger the number, the smaller the design cube/plane can be. The smaller the number, the less precision but the larger the design cube/plane. The size of the design plane changes as different values are entered here.
- Click OK to close the Advanced dialog box.
- Click OK to close the Settings dialog box.
- Set the global origin. In Microstation, the global origin is the center of the 2D design plane (3D design cube).
Select the Utilities > Key-In option from the drop-down menu. In the Key-in dialog box that appears, type:
GO=<Global Origin X>,<Global Origin Y>
Where <Global Origin X> and <Global Origin Y> are from the calculation above.
- Select the Save Setting option from the file menu.
Failing to save causes the changes to be ignored.
- Save the new file. A seed file is now ready for use with the Export to CAD tool that matches the feature classes.