Startup Location, Project Base Point and Survey Point

Every project has a startup location (true origin), project base point and a survey point, although they might not be visible in all views, because of visibility settings and view clippings. They cannot be deleted.
The startup location is the internal project origin and fixed on the plate having 1 mile (10 miles for 2011) radius. It is equivalent to the WCS Origin in a CAD (.dwg). Based on that origin and coordinate system, you can then have multiple locations in the form of shared coordinate systems with their own origin and orientations. So if you want to move your linked files around, you have to link them by Shared Coordinates and not by Origin to Origin as that will always land them at the same spot.
The project base point defines the origin (0,0,0) of the project coordinate system. It also can be used to position the building on the site and for locating the design elements of a building during construction. Spot coordinates and spot elevations that reference the project coordinate system are displayed relative to this point.

The survey point represents a known point in the physical world, such as a geodetic survey marker. The survey point is used to correctly orient the building geometry in another coordinate system, such as the coordinate system used in a civil engineering application.

Consider the following when working with project base points and survey points:

• To ensure accuracy of the model, be sure the model geometry is less than 1 mile (10  miles for 2011) from the startup location of the project base point. To check this measurement:
1. Use Move to Startup Location from the shortcut menu to move the project base point back to its startup location.
2. Use the Measure tool on the Modify tab to measure the distance from the project base point to the model geometry.
3. If the distance is more than 1 mile (10 miles for 2011), move the model geometry within 1 mile (10 miles for 2011) of the startup location of the project base point.
• Before you export a building site to a civil engineering application that accepts ADSK files, such as Civil 3D:
1. Move the unclipped survey point to the location agreed upon with the civil engineer.
2. Use the Specify Coordinates at a Point tool or enter the coordinates on the Site tab of the Building Site Export dialog, using the coordinates provided by the civil engineer.  
• To ensure that an imported DWG site is positioned correctly in the project: 
1. Using the coordinates you received from the civil engineer, specify the shared coordinates of the survey point.
2. Specify the correct angle for True North. Specify Positioning-Auto by Shared Coordinates to link the DWG file.