About the ArcScene coordinate system
If all the data you want to display in ArcScene is stored in the same coordinate system—for example, if you're using your organization's database—you can just add it to a scene without considering whether the layers will overlay properly; they will. If, however, you've collected data from a variety of sources, you'll need to know what coordinate system each dataset uses to ensure ArcScene can display them together.
When you add a layer to an empty ArcScene document, that layer sets the coordinate system for the scene; you can change it later if necessary. As you add subsequent layers, they are automatically transformed to the scene's coordinate system as long as there's enough information associated with the layer's data source to determine its current coordinate system. If there isn't enough information, ArcScene will be unable to align the data and display it correctly. In this case, you'll have to supply the necessary coordinate system information yourself.
ArcScene expects coordinate system information to be stored with the data source. For a layer in a geodatabase, this information is part of the layer's metadata. For coverages, shapefiles, triangulated irregular networks (TINs), and rasters, it's stored on disk in a separate file named after the data source but with a .prj file extension (for example, streets.prj). These files are optional files; thus you may still need to define the coordinate system for one of these data sources. You can create a .prj file with ArcCatalog.
If no coordinate system information is associated with a data source, ArcScene will examine the coordinate values to see whether they fall within a range: from -180 through 180 for x-values and from -90 through 90 for y-values. If they do, ArcScene interprets them as geographic coordinates of latitude and longitude. If the values are not in this range, ArcScene simply treats the values as planar x,y coordinates.
ArcGlobe displays using one particular coordinate system—Cube Projection. All data added to an empty ArcGlobe document is projected onthefly to this coordinate system. Data that does not have projection information associated with it cannot be added into ArcGlobe.