A special mode of mapping is sparse mapping. This is a sequence of irregularly spaced positions within an area of 3 degrees in diameter, i. e. the maximum separation between any two pointings must not exceed 3 degrees. Contrary to the normal mapping modes, multi-filter observations are carried out such that the complete set of requested filters is measured at each position before moving to the next position. This mode facilitates observations of a cluster of sources in a small area. As the detector remains switched-on all the time the signal stability is increased and the times for overheads are reduced (cf. Sect. 6.3). Additionally, the dynamic range of the detector can be adjusted to the brightness at each individual position.