Comparison of distance error distributions between test binaries within a GC and the overlapping MW disc DWDs, for each of the 20 GCs in our sample. The blue lines are the weighted sums of the distance distributions of the overlapping MW DWDs for each GC. The other coloured lines add to this distribution a test binary at the distance of the GC with a certain S/N. The dashed black lines mark the distance of each GC.