Identifying an Unknown Source Projection for Spatial Data in Map 3D or Civil 3D

Have you ever tried to insert geolocated data or imagery into either AutoCAD Map 3D or Autodesk Civil 3D only to have it end up miles away from your project area?  Chances are that the software just does not know where to place the data relative to yours because either:

  • You do not have your coordinate system defined in your drawing
  • The files you are using do not have a readable coordinate system definition to use for a projection.

Below are a few steps that you can take in order to eliminate most projection issues.

Make sure that your drawing coordinate system is defined

This may sound obvious, but some templates do not define the coordinate system for the user.  Instead, the user is either supposed to know which projection to use, or in the case of smaller firms, they assume that every job will be in the same state plane system and therefore defining the coordinate system is unnecessary.

Checking the existing coordinate system in Map 3D

Knowing if you have a coordinate system defining in your drawing in Map 3D is simple because it is located right in the status bar.  At the bottom of the screen near the middle, you should see a globe icon with either the shorthand for the coordinate system just to the right of it or the word <none>.  If there is no projection defined, click the down arrow right next to <none> and define it.

01

Checking the existing coordinate system in Civil 3D

While the drawing is open, click on the Application menu (Civil 3D/Map 3D icon at the top left) and go to drawing utilities>drawing settings.  When the Drawing Settings dialog box appears, define the projection in the Units and Zones tab.

02

Attempting to connect to spatial data

Now that you have defined your coordinate system to give your spatial data a location on which to project, open the Map Task Pane (command: MAPWSPACE) add a connection to the data by the appropriate data type.  From the Display Manger tab, click on the stack icon called Data and select Connect to Data to open the data connection dialog.

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On the left-hand pane of the dialog, select the data source that you are using for a connection.  Give the connection a name that you can recognize and click the icon on the right-hand pane to select the file that you are trying to connect.  Note: you also have the option to connect to every file in a folder by selecting the folder icon.  In my example, I will use an aerial TIF file, which is a raster image. 

04

Click Connect.  With luck, the coordinate system will be identified as shown below and you can just select Add to Map.

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If, however, you do not see a coordinate system and instead see <unknown> in the Coordinate System column, you will need to do some digging.

Sources of Coordinate Systems for unknown/unidentified systems

Having “<unknown>” appear in your coordinate system could be a sign of a few different issues, but most likely it is because the data system that you are trying to use is not embedded in the file or collection of files that you are using.  If the data came from a free data repository (EG. USGS Earth Explorer), then you should be able to find the projection by searching the metadata.  Other times, data sources will include a text file that will also give you the projection definition.  These “unknown” systems can always be overridden in the connection dialog by selecting the line you wish to override, right-click, select Edit Coordinate System and place the correct projection into the Override column.

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About the Author

Randy McCollum

Civil Solutions Applications Expert<br><br>As a professionally licensed civil engineer Randy provides training, process optimization, and technical support in water resource and site designs. His involvements include a wide range of product types including AutoCAD, Civil 3D, Map 3D, Autodesk Storm and Sanitary Analysis, Raster Design, and Infraworks.

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