Before we can analyze or do any other fun things with a surface, we have to make one! To the land development company today, this can mean pulling information from a large number of sources, including Internet sources, old drawings, and fieldwork. Working with each requires some level of knowledge about the reliability of the information and how to handle it in Civil 3D. In this section, we'll look at obtaining data from a couple of free sources and into your drawing, creating new surfaces in both TIN and grid formats, and making a volume surface.

Before moving on to creating the surface, let's look at the components that can be used as part of the definition:

• LandXML files These typically come from an outside source or are exported from another project. LandXML has become the lingua franca of the land development industry. These files include information about points and triangulation, making replication of the original surface a snap.

• TIN files Typically, a TIN file will come from a land development project that you or a peer worked on. These files contain the baseline TIN information from the original surface and can be used to replicate it easily.

• DEM files Digital Elevation Model (DEM) files are the standard format files from governmental agencies and GIS systems. These files are typically very large in scale, but can be great for planning purposes.

• Point files Point files work well when you're working with large data sets...