Figure 6.

The effect of adding synthetic noise to the displacement data. The graph shows the values of the error function P_err plotted against the RMS noise level for each of the three virtual fields; this was repeated twice so that there are two sets of points. It is evident that there was no systematic bias in the error function $P_{\mathrm{err}}^{\mathrm{total}}$ as a result of adding noise and that the three virtual fields were affected independently and differently.