The effect of tamping space and pattern in dynamic compaction has been investigated on loose dry sand using particle image velocimetry technique. A small-scale physical model of dynamic compaction was prepared. Tamping was executed by rising and dropping semi-cylindrical steel tampers on sand deposit at two points with different distances. In all the tests, the weight of the tampers and drop height were kept constant. Digital photographs were taken after each drop. Using image processing on sequences of digital images, soil deformation and the effect of each drop on the soil improvement were obtained. The diagram of relative density increase against normalised depth has been plotted for different tamping spaces, and it can be used for achieving the optimum tamping distance in order to obtain efficient density at a given depth. The results also show that the tamping space about four times of tamper diameter (4D) is the most efficient in dry sand improvement. Tamping pattern can also influence the compaction results. Further soil improvement occurs with tamping alternatively at the adjacent tamping points.