Spotting enemy in a limited terrain hex from an elevated spotting hex

[brad_newcomer]

Had a discussion come up in a game this afternoon about spotting units in limited terrain (i.e. a FIELD to be exact).  Usually, they can only be spotted if the spotting unit is within 3 hexes from it.   However, what happens if the spotting unit is at an elevation of 20-feet (i.e. on top of a hill)?   Normally, spotting units get a +6-hex increase in their spotting range (unless there are weather and/or night issues).   However, do they also get an increased range to spot units in limited terrain.   My gaming buddy and I came to a consensus that limited terrain is limited terrain even if being spotted from elevation (i.e., both cases would have to follow under the 3 hex limit to being able to spot).    

What does everyone else think about this situation?    Would you handle all limited terrain spotting situations equivalent (i.e., regardless of spotting unit elevation)?