AutoCAD Civil 3D uses conversion factors if the LandXML file you are importing has different units from the current drawing.
You can import LandXML files that use feet or meters.
When imported, the LandXML files are converted to the units of the current drawing. In AutoCAD Civil 3D, the default drawing units can be meters, International Feet, or U.S. Survey Feet.
Unit conversion is not applied to descriptive LandXML attributes that may contain numeric values. For example, if you are importing a point with the description “12 oak” into a metric project, it will not be changed to “305mm oak.”
LandXML does not transform coordinate systems automatically. No specific coordinate system transformation is applied other than what is specified by the translation and rotation settings.