  We investigate the effects of observatory locations on the probability of
discovering optical/infrared counterparts of gravitational wave sources. We
show that for the LIGO--Virgo network, the odds of discovering optical/infrared
(OIR) counterparts show some latitude dependence, but weak or no longitudinal
dependence. A stronger effect is seen to arise from the timing of LIGO/Virgo
observing runs, with northern OIR observatories having better chances of
finding the counterparts in northern winters. Assuming identical technical
capabilities, the tentative mid-2017 three-detector network observing favors
southern OIR observatories for discovery of EM counterparts.
