How do I convert a 2D section drawn in CAD into 3D polyline in ArcGIS. By 3D polyline I mean PolylineM(Z).
I have 300 sections. Drafting it manually seems a bit laborious.
Convert your CAD polylines to a shapefile or feature class then:
Using ArcGIS 9.3.1 the 3D Analyst toolbar in ArcScene you could use the Convert Feature to 3D tool.
Using ArcGIS 10 you could use the Feature To 3D By Attribute tool.
You can also use the Shape to ShapeZ tool from ET Geowizards.
If I had FME (or the Data Interoperability Extension) then I would use the CoordinateSwapper transformer to switch the Y and Z axes. The NeighborFinder transformer could be used to pick the nearest text label in order to determine the elevation.