I don't see any point in using both of this tags. In most cases they are used simultaneously when the topic involves coordinates in lat/lon. Not only latitude AND longitude are always involved simultaneously (I haven't seen any question where only one of this tags could be applied and not both of them) - so it would be more appropriate to use tag named 'lat/lon' or something like that; but the common sense tells us that these questions are about coordinates and actually there is nothing special in latitude or longitude and we already have the 'coordinates' tag.
I believe that these two tags should be deleted because they provide no help at all and 'coordinates' tag is already there.