Surveyors often produce various file format for the terrain that they have surveyed. One common format is .XYZ
Luckily the Cadimage Sites + Massing tool has created a function where you can import an XYZ file directly to a mesh.
One thing to note is that often the surveyors will export the file in Unicode format.
Easy Solution: Open the file in Notepad & save it again in ANSI format