A compaction control system for and methods of accurately determining properties of compacted and/or existing ground materials. The compaction control system includes a compaction machine that further includes a vibratory drum (or roller). The compaction machine is equipped with sensors to determine position and heading, vibration amplitudes at selected frequencies, and material type and moisture content information. Further, the compaction control system includes a controller and certain algorithms for processing the sensor information. Namely, a method is provided of using the sensor information to assess the improvement in compaction and then determine whether and/or when further ground improvement solutions are needed.