Civil 3D Tip: How to Convert DWG to KML
KML files are used to quickly display proposed drawing information overlaid on real-world conditions in Google Earth.
First, set or verify that the datum is properly set in your drawing. Similar to the process explored in a previous tip, you will go to the Settings tab in the Prospector. At the top, locate the name of your drawing, highlight by selecting the text, then right-click. Choose Edit Drawing Settings.
This will open the Drawing Settings dialog box. In the first tab, Units and Zone, verify that the units are set as desired. In this case, we will be using Feet. If no datum is shown, you will want to set the Category. Usually this will be Country or State. You will then want to click in the drop-down arrow under Available coordinate systems and select the datum you wish to project into. If you are unsure as to which datum you should be using or if the zone fails to project, verify with the surveyor. Once these are set, the remaining information under this tab should auto-populate for you. Once complete, click OK. The coordinates will be set for the drawing.
Note: This is not a project-wide setting. Datum settings are drawing-specific.
You can verify that the coordinate system is set when the Geolocation tab is available in the Ribbon at the top of your screen.
It is best practice to isolate the items you wish to add to the KMZ prior to initiating the command. Exportable items include:
- Alignments – Centerlines and station labels
- COGO Points – Survey points and markers
- Feature Lines
- Parcels – Boundaries and segment text
- Pipe Networks – Gravity and pressure pipes and associated structures
- Standard AutoCAD Geometry – Lines, polylines, hatches, blocks, and text
- Surfaces – Triangles, boundaries, or contours
- Survey Figures
To prepare a KML or KMZ file:
- In the Prospector, on the Toolbox tab, expand Miscellaneous Utilities > Export KML and double-click.
- On the General page of the Export KML wizard, specify a name and (optionally) a description and hyperlink for the file. Select Next to progress to Objects.
- On the Objects page, specify the objects to export. You can choose all objects or select items on the screen by clicking the plus sign. Click Next to progress to Geo-Reference.
- On the Geo-Reference page, if the drawing coordinates are properly set, you will find the Drawing Coordinate System Transform preselected. You can also specify a User-Defined Transform to transform the coordinates of the drawing data to geographic coordinates. This is done by identifying a specific point in the drawing (X/Y coordinates) and associating it with real-world coordinates (latitude and longitude). Note that X corresponds with longitude and Y corresponds to latitude. Sometimes a rotation is needed in the coordinate transformation. Then select Next to progress to Nudge.
- On the Nudge page, you may need to incorporate these factors in order to fine-tune the location of the created model. Click Next to progress to File.
- On the File page, specify the file name, location, and file extension (KML or KMZ). You can export the file to .kml (uncompressed) or .kmz (compressed) format. Click Export to export the file.
Note: This process may take a few minutes to execute.
The differences in the file types include:
KML – Plain text (XML), only stores geographic code and text, easy to read and edit in a text editor, larger (uncompressed)
KMZ – Compressed zip archive, stores the main KML plus images, icons, and 3D models, smaller and faster to download, must be unzipped to edit the code inside
- On the Export and View page, you can click View to view the exported file.
- Google Earth will open. The newly-created KML file will populate under Temporary Places. Click on the arrow next to Model to see and toggle the added items on and off.
You can select KML items in Google Earth to view their embedded properties.
Note: When the level of detail view is turned on, surfaces may not be exported correctly. If you notice that a surface is not exported, turn the level of detail view off and then re-export the drawing.
Note: For metric drawings, when the AutoCAD Insertion Scale units are set to Unitless, the Export KML command converts the metric units to equivalent inch values. When the units are set to Feet, the Export KML command converts the metric units to equivalent values in feet.
