As an example of a problem that can occur: Client wants to survey the elevations of a parcel of land for building a house. The surveyor goes out and collects data with gps survey equipment, which produces a .csv file of northing,easting,and elevation values relative to some National Geodetic Survey benchmark. The engineer imports this .csv into his cad software, produces a grading plan .csv file. The earthmoving contractor imports the grading plan into his software and grades the site.<p>Client gets house built, moves in and discovers that the front yard turns into a swamp after every rain.<p>Somewhere in the chain of importing and exporting .csv files, software A was using survey feet and software B was using international feet.<p>This can also cause problems like structures built in the wrong spot, fences built on neighbors land, etc.