Why are the height values different although the altitude values in the "straight-in approach" and "circling" minimums are the same? For Adana airport, the minimum altitudes of the 05 runway VOR Z approach are the same (1200) but the heights are different (1148-1137). What is the reason for this? Is it due to the elevation of the region where the minimums are located? So where is the "circling" minimum accepted? The name of the chart document in Turkey AIP for LTAF airport is "AD 2 LTAF IAC - 2".
Straight-in is referenced to a particular runway, while circling is referenced to the airport elevation. The same elevation MSL is thus a different height above the referenced elevation.
The "runway elevation" for a particular runway is generally defined either as the highest point in the touchdown zone for that runway, or the elevation of the threshold. Thus the runway elevation can differ at opposite ends of the same physical runway. And the airport elevation, being the highest of these (or perhaps the highest landable surface - if a runway slopes down from the center in both directions), will often differ from several of the runway elevations on that airfield.
The salient point, though, isn't in the specific definition of each concept, but in the fact that a straight-in approach is referenced to its runway, while a circling approach, being not-runway-specific, is referenced to the airport.