Have to admit I hadn't noticed you could get that info from the city screen, but as a mapmaker I'm used to dealing with the coordinates. They are measured from the bottom left (SW) corner of the map, so I think you'd be correct that on a 52-tile-tall map, Y=29 would be near the equator - just North of it. I think even on a cylindrical map, you might deduce some useful information from the X coordinate: It tells you how far you are from the longitude where the map wraps around, and you can relate that to your knowledge of the map script - for example, some of the continent-based scripts will generally have nothing but ocean at the wrap-around point. If it's a map-script that is normally flat (such as great plains), but the map-maker has changed it to cylindrical (I've done that a few times) then knowing your longitude might be very helpful.
