As mentioned before - these are not standard terms
what you have is
-altitude @ ISA 1013 hpa - same as FL
-altitude @ current QNH (and ISA temp)
-temp corrected altitude at QNH
in addition, a lot of people use now:
- GPS altitude: GPS calculated altitude against the WGS84 model
mathematically more precise and no issues from changes in temp and pressure, but carries the issues of Mother Earth not fully conforming to the WGS84 ellipsoid
whatever you use, make sure there are at least 3feet between you and the nearest thing beneath you
