Lets say I have a object on level 3 and it has the ability to show its elevation. This elevation is 900cm where 3 x 250 is the elevation of story 3 + its placed 150cm above its home elevation...
I can count this elevation by using :
Obect_elevation = GLOB_HSTORY_ELEV + GLOB_ELEVATION
And now I would like to know, what is this objects elevation relative to the the 1st and 2nd Refence Level.
I found it 
ref_elev_2, ref_elev_3 are 1-st and 2-nd level and
ref_elev_4 is the sea level...
Found here:
http://gdl.graphisoft.com/gdl-docs/gdl-guide/chapter-12-miscellaneous/request-options/
m = REQUEST ("REFERENCE_LEVEL_DATA", "", ref_name_1, ref_elev_1, ref_name_2, ref_elev_2, ref_name_3, ref_elev_3, ref_name_4, ref_elev_4)
where ref_elev_1 is the project zero, ref_elev_2, ref_elev_3 are 1-st and 2-nd level and
ref_elev_4 is the sea level...
Found here:
