Each NGS technology generates a consistent pattern of non-uniform sequence coverage. (a) Sequence coverage depth is displayed as a gray-scale (0-100× for Roche 454; 0-500× for Illumina GA and ABI SOLiD) along an approximately 25-kb region of chromosome 11 amplified by three long-range PCR products (red rectangles). (b) A heat-map colored matrix displays the coefficient of correlation of coverage across the entire 260 kb of analyzed sequence between each of the 72 possible pair-wise comparisons (four samples by three technologies). The apparent lower correlation of the Roche-454 sequence coverage is more reflective of the smaller amplitude in the coverage variability (lower average coefficient of variance) than a lack of coverage correlation from sample to sample. The correlation of NA17460 with the other three samples on the ABI SOLiD platform is slightly lower due to technological issues (Additional data file 2) and was therefore excluded from the coefficient of correlation calculation reported in the text.