FAQ: How does ArcGIS read elevations from 3D AutoCAD polylines?
How does ArcGIS read elevations from 3D AutoCAD polylines?
ArcGIS will read and display the elevation values for all supported entities, which includes 3D polylines. In situations where all of the vertices of a polyline feature do not share the same Z coordinate values, ArcGIS will take the first vertex it encounters and use that Z value for all vertices that form the polyline. The order of vertices is determined by the to-from direction of the line.