The standard maximum likelihood technique is applied to a pre-selected list of source positions. This list may either be a source catalogue or the result of another detection technique (LDETECT, MDETECT). In order to get an unbiased input to the maximum likelihood technique an equidistant position grid can be used. Such a grid can be created with the command CREATE/GRID_TABLE in EXSAS. The position grid has to be passed to the COMPUTE/UPPER_LIMITS command as a user list with the positions kept fixed. The result list from the detection, UL_LIST_ALL has then to be converted into a likelihood image with the command CONVERT/SOURCE_TABLE. The spacing of the position grid should be adjusted to the size of the point spread function.