Working with elevation data
Esri Roads and Highways supports 3D elevation data on source geometry and centerline vertices.
If you choose to use a redline as your source geometry, then the redline can support z-enablement.
Being able to edit in 3D helps provide context to your geographic data. You can visualize more realistically your creation and placement of features, as well as easily fix errors or change values in the 3D space. Setting the height, or z-value, of the GIS features being edited is a critical part of the 3D editing experience.
Many features—such as benches or roads that lie on an elevation surface—do not need a z-value at all, but rather, can be 2D features that get their displayed heights assigned on the fly from an underlying surface layer. Other features—such as viewpoints on top of structures or 3D flight paths—need z-values to define their position in 3D space that is distinct from a surface.
M- and Z-enabled vertices
Vertices can store additional information besides x, y locations. The attributes include m-values and z-values, which are often used to store information about route measures and elevation.
To add m- or z-values to a vertex, you must have specified that the feature class be able to store them when you created the feature class. If you did not set this property, you need to create a new feature class and import the existing features into it.