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tokens: for pairs of one-dimensional posteriors on the HL time of flight (Fig. 3 ). We see that with the HL network (solid lines), for 50percent of the skymaps the fidelity is above 0.8 for CBC-burst skymaps, and above 0.9 for LIB - cWB skymaps. The CBC-burst fidelity is a bit lower for the HLV network, while the LIB - cWB median fidelity stays close to 0.9. The two burst algorithms thus select the same sky ring very often. Strong correlation exists between the fidelity of the full skymap and that of the time of flight, implying that when slightly different rings are selected (low t HL fidelity) the overall fidelity is strongly reduced. Thus, the disagreement we found while comparing the full skymaps, Fig. 1 , is determined by both the placement of probability around the ring and the position of the ring itself, with the latter happening less frequently but having a large impact when present. Figure 3. The cumulative distribution of time-of-flight fidelity for pairs of algorithms in the HL (solid lines) and HLV (dashed lines) analyses. Fig. 4 shows the clear correlation between angular offsets and decreased fidelity using data from the HL network, as well as the corresponding values from GW150914 (stars), which fall within the scatter observed in simulations. We note that while there is quite a bit of scatter, the general trends seem to be independent of which algorithms are actually compared. This further suggests that low fidelity is driven by differences in the selected triangulation rings, because all algorithms produce triangulation rings. Figure 4. A scatter plot of the fidelity using the full skymap and the angular separation between triangulation rings. GW150914s values are shown as stars. We mentioned above that the GW150914 fidelity for LIB cWB was much lower than average. We can now understand why the LIB and cWB skymaps for GW150914 have support on different sky rings (see Abbott etal. 2016f ). They thus belong to this rarer class of reconstructed skymaps for which there is a significant drop of fidelity. Furthermore, one can compute the distribution of the angular distance between rings. We find that the distributions look unimodal, with mean smaller than 0.2 for all pairs of algorithms, and standard deviations in the range 2.54 (2.57) for the HL (HLV) network. 3.2 Searched area So far we have focused on the degree of similarity of skymaps, which was naturally prompted by the fact that burst and CBC skymaps were so different for GW150914. However, that is probably not the most relevant figure of merit to assess the chances of a successful EM follow-up. The fact that a skymap is larger or different might not lead to wasted telescope observation time as long as most of the probability is at the true position. In this section, we report the searched area found by the burst and CBC algorithms. We define the searched area as the amount of sky one needs to image, starting from the most likely skymap pixel and going down, until the true