Spatial distribution of error rate variation. For each error type and sequence length, the x-axis represents the spatial location of 454 reads and the y-axis represents the y-coordinates on the PT plate. The results presented in this figure correspond to plate #1. Data for the other two runs is presented in additional file 4. The 15 strips represent the 15 regions. We display separately the four types of error (insertions, deletions, mismatches and ambiguous base calls) and the length of the sequences generated. Colors indicate the ranges of error rates, from 0 to 1 (or the length of the sequences, from 0 to 500), using a sliding window (see materials and methods).