The Standard Instrument Local Environmental Plan is the form that control on development height usually takes, and it states that ‘The height of a building on any land is not to exceed the maximum height shown for the land0000000 on the Height of Buildings Map. ‘Building height’ for that purpose, is taken to mean either the vertical distance from ground level (existing) to the highest point of the building, or the vertical distance from the Australian Height Datum to the highest point of the building (excluding communication devices, antennae, satellite dishes, masts, flagpoles, chimneys, or flues). The precise ‘ground level (existing)’ can be difficult to calculate, particularly where there is no soil or garden on the suite area around the building, or where excavation below ground has occurred. These sorts of issues are particularly relevant in development applications where view loss might occur.
The leading case on determining ‘ground-level (existing)’ on sloping land or land that has been completely excavated is Better v Council of the City of Sydney  NSWLEC 1070. In that case the plaintiff sought consent for a residential building on a site where an existing building already occupied the entire site, and there was no longer any ‘ground’ for determining the existing ground level, and there was an existing part-basement excavated into one part of the site. The Commissioner found that once the existing building is demolished, the ground levels of that prior building would no longer be discernible or relevant as a starting point for measuring the height of any new building, and that it would be conceivable that surrounding properties could have starkly different height limits arising from the same development standard. The Court preferred the approach that the existing ground level could be determined by extrapolating the ground levels on the footpath across the site to measure the vertical distance to the highest point of the building, as it resembled the overall topography of the site, and would remain relevant once the existing building was demolished.