This plot shows the largest gap (in pixels) between identified lines
in FMTCHK (1-pinhole arc) and 2DMAP (9-pinhole arc) data. We also show
the number of the order in which the gap appears.
More information can be found in the
<a href="http://www.eso.org/observing/dfo/quality/XSHOOTER/qc/distortion_qc1.html">plot tutorial page</a>.