Example heat map showing several commonly observed quality defects. Nucleotide positions 1-75 are plotted from left-to-right along the x-axis; tiles 1-100 are ranked from top-to-bottom along the y-axis. (These numbers may vary for other datasets). The scale depicts the mean probability of observing a base call error for each tile at each nucleotide position. The defects evident in this dataset (see text for details) are atypical of Illumina sequencing; this dataset was chosen specifically to illustrate the capabilities of SolexaQA.