Markwg

We would like to locate our site model at the correct height in real world terms Our ground floor RL is 78.1 But our preference is to have have our ground floor located at elevation 0 so that our window schedule shows the sill heights at, say 900mm above floor level rather than RL 79000 So my question is, is there a way to link the ground floor layer with its real world elevation (RL 72.1) but keep it at Elevation 0 at the same time?