Georeferencing

Hi, when I compare my map to ground control I shoot with cm-level Trimble GNSS (all datums are WGS84, I am not doing any datum transformation and I am using a WGS84 defined base station reference point), my map data appears to be off by about 6ft to the north of where the GPS (and other local data sources) say it should be...Any suggestions?  If I provide actual ground control points would that work better?