I am using MAP 3D 2005...
here is a what the help files have to say about dgn's
Autodesk Map supports MicroStation version 8 and 7 files. Bentley Systems,
Inc. and MicroStation programs use the DGN format, which is similar to a DWG
file; there can be points, lines, areas, text, and other object types
present in the same file.
All geometry in MicroStation is stored using a 9 digit integer. Due to this
design, it is important to understand that it is possible to lose precision
if you export drawing data with large coordinate values. The MicroStation
seed file used for export will have a dramatic effect on the resulting DGN
data.
For specific information on MicroStation DGN format, read the sections
below. For general information on using the Import or Export commands, see
Overview of Importing and Overview of Exporting.
Importing
Data-element information is stored in an external database file and linked
to graphic objects. Autodesk Map imports database link information so you
can maintain the linkage during import.
By default, object colors are imported to their closest ACI (AutoCAD Color
Index) color. If you want to import object colors using RGB (True Color),
you must edit the mapimport.ini file. For more information, see Customizing
the .ini File.
Note If Autodesk Map detects that the DGN file being imported is empty
(i.e., contains no objects), an error message is displayed.
Driver Options
You can set the following options when importing DGN files:
Option Description
Group Elements By Choose how you want to group the incoming elements.
Select Geometry to group objects by entity type. All objects of the
same type will be imported to the same layer in the Autodesk Map drawing.
Select Level to group objects by the DGN level. All objects in the
same level will be imported to the same layer in the Autodesk Map drawing.
Select Schema to group objects by schema.
Tags Select the Display check box to display DGN tags (user-defined
attributes attached to elements in the DGN file).
Expand Cells This option is overwritten by the CELLS=BLOCKS setting in
the mapimport.ini file. Edit mapimport.ini to change the setting.
Linkage Extraction Allows you to extract MSLinks and FRAMME attribute
linkage values from the DGN file.
If you select MSLinks, Autodesk Map imports up to three links per
object. For each link, two fields are added to the object data table:
mslinks_n, which specifies the key value, and entity_num_n, which specifies
the table.
If you select FRAMME, the following fields are added to the object
data table: comp_count, comp_num, dgnfile, feat_num, state_num, and ufid.
Coordinate Units Each DGN file defines a UOR (unit of resolution); in
addition, it can have definitions for Sub units and Master units. Select
Master, Sub, or UOR to specify which of these units in the DGN file matches
the default unit in the Autodesk Map drawing. For example, if the default
unit in your Autodesk Map drawing is meters, and meters are the Sub unit in
the imported file, select Sub.
If you select Sub or Master, the UORs in the DGN file are converted to
Sub or Master units according to the conversion factor in the DGN file
header. If you select UOR, the UORs in the DGN file are imported directly
with no conversion. The default unit is Sub.
Complex Strings Select Drop if you want each component of a complex
chain to be returned as its own feature and no feature will be returned for
the complex chain as a whole. Otherwise all elements of the complex chain
will be merged into a single linear feature, any arcs in the complex chain
will be converted into linestrings and any linkages on the component
elements themselves will be lost.
Select Propagate Member Linkages if you want the linkages attached to
the first component of the complex chain to be returned on the feature,
supplementing any existing linkages. Otherwise any linkages on the component
elements themselves will be lost and only those linkages attached to the
complex chain itself will be returned.
Text Select the Split Multi Text check box or clear it.
Note If you do not want to change options in the dialog box, click Cancel
to close the dialog box. Clicking OK can change the settings.
Other Import Options
You can set a number of options in the MapForeignFileProperties.ini file.
Exporting
Every DGN file requires a seed file to give it default information (similar
to the acad.dwg prototype or template file). The seed file controls working
units, global origin, the version you want to export, etc. Several seed
files ship with Autodesk Map.
The default file, lrgseed.dgn, is a three-dimensional seed file for a
version 7 DGN file.
If you want to export to a two dimensional DGN file, you must change to a
two dimensional seed file. Likewise, if you want a specific global origin or
specific working units, reference the file name of the desired seed file.
The global origin and units of resolution should be set in a seed file that
is appropriate to your Autodesk Map drawing coordinates.
To export a version 8 DGN file, you must change to a version 8 seed file,
for example, C:\Program Files\Common Files\Autodesk
Shared\GIS\ImportExport\3.0\design\seed3d_ft_v8.dgn.
The seed file you use significantly affects the outcome of the export
process. If the design plane coordinate bounds in the seed file do not fully
contain the extents of the Autodesk Map drawing, Autodesk Map will not
export objects. In this case, use a seed file that works for your region and
coordinate system. As a last resort, select the driver option Compute
Optimal Seed File Parameters.
To change the seed file for a single file
1.. In the Export dialog box, click the Options tab.
2.. Click the Driver Options button.
3.. In the Design File Output Settings dialog box, under Seed File, click
the [...] button.
4.. In the Select Seed File dialog box, navigate to the location of the
seed file you want to use, select the file, and then click Open.
Note If you are a limited rights user, be sure that the seed file is in a
location where you have access to it.
To change the default seed file
1.. Open the mapexport.ini file using a text editor such as WordPad.
This file is in the C:\Documents and Settings\All Users\Application
Data\Autodesk\Autodesk Map 3D 2005\R16.1 folder.
2.. Find the [IGDS] section. This is where the default seed file is
specified.
3.. Change the default seed file to the seed file you want.
For example: Driver:RUNTIME_MACROS=_SEED,"C:\Program Files\Common
Files\Autodesk Shared\GIS\ImportExport\3.0\design\seed3d_ft.dgn".
4.. Save and close the .ini file.
Additional Notes
Closed objects are not filled, even if they were filled originally.
Hatch patterns are not exported. If you export polygon data that is hatched
in Autodesk Map, the resulting data will not be filled in MicroStation.
Driver Options
You can set the following options when exporting DGN files:
Option Description
Coordinate Units Select the coordinate units of the features: Master,
Sub, or UOR. Select the unit that matches the default unit in your Autodesk
Map drawing. For example, if the default unit in your Autodesk Map drawing
is meters, and you are using a seed file that defines meters as the Master
unit, then select Master. The default is the Sub unit.
Two Point Line Output Select Type 3 Elements or Type 4 Elements.
Allow Area Fills Controls whether or not fill linkages will be written
out for ellipses, shapes, and solids. Select Yes or No.
Seed File Select the seed file, which controls whether or not the
output DGN file is two-dimensional or three-dimensional, sets the coordinate
units, sets global origin, etc.
Compute Optimal Seed File Parameters Select this option to override
all seed file settings and have Autodesk Map calculate the settings for you.
Autodesk Map determines the largest dimension for the set of exported
objects and sets the appropriate range and precision. It sets the UOR per
Sub to 10, and sets the Global Origin to the center of the bounding
rectangle of the exported objects.
Override Global Origin Select this option to override the global
origin setting in the seed file. Then specify the global origin you want to
use.
Override Units Select this option to override the units setting in the
seed file. Then specify the units setting you want to use.
Cell Library File You can optionally select a file to use as the cell
library, which contains definitions of symbols that can be placed in the
output DGN file.
Note If you do not want to change options in the dialog box, click Cancel
to close the dialog box. Clicking OK can change the settings.
"Frazer Andrews" wrote in message
news:28539560.1109167596157.JavaMail.jive@jiveforum2.autodesk.com...
> Apologies for previous post - options are there after all. Do you know if
> this is limited to particular versions of DGNs?