I would like to have an additional reference level that allows for site surveys where a Temporary Benchmark (TBM) was used by the surveyor instead of the specific height above sea level.
Please see the attached 'photoshopped' screen-capture to show what I'd like to see. In this example, the surveyor used an arbitrary TBM set at 50.00, but the actual altitude is over 100m
Altitude has increasing relevance to other aspects of the design process than mere height above sea level (eg. shadow calculations, optimising solar panel orientation). So, when a surveyor uses a TBM, it's useful to have that as a reference level IN ADDITION TO the actual altitude of the site, rather than changing the altitude to suit an arbitrary TBM and thereby screwing things up elsewhere.