If you want to export to Google Earth objects that you have created in AutoCAD, but your drawing is not based on a specific coordinate system, here is the procedure you need to follow:
Step 1: Click on the "Publish to Google Earth" command.
Step 2: Select the objects you want to export.
When you are finised, press "Enter" to complete your selection.
Step 3: Choose "User-defined trasformation" as the coordinate transformation method
(if you have enabled the quick wizard mode, press on "Back" twice, to get to these dialog box options)
Then click on the top "+" button in the "Drawing location (X/Y)" section, to pick a point in your drawing which you are goint to assosiate with a specific position in Google Earth.
You can also specify an orientation by clicking on the second "+" button if your project is not aligned correctly.
Step 4: Select a reference point in your drawing
You will be returned to the dialog box. Press "Pick from Google Earth"
Step 5: Choose the corresponding location in Google Earth
A crosshair will appear in your Google Earth window. Use this to specify a posistion which corresponds to the point in your drawing and then return to AutoCAD and press "OK" in the pop-up dialog box that has appeared.
Then quickly go through the remaining publishing options. If you need more information on any of them, consult this tutorial.
Step 6: Your project is published into Google Earth
Note that Plex.Earth has created a structured model or your project inside Google Earth's Temporary Places with each folder representing a layer of your original drawing.
Step 7: View your project from any angle
You can now see and present your project in its actual location at any zoom level and from any angle!