Methods and apparatus for determining whether soil is satisfactorily compacted. An operator delivers impact energy to the soil, and the amount of impact energy transmitted through the soil is repeatedly sensed and stored. A modelling formula, which approximates the variation of the stored amounts of impact energy, is used to generate current and target values for the level of compaction; if the current value equals or exceeds the target value, the soil is considered to be satisfactorily compacted.
