Hey, the beach is 200km horizontally but only 34m vertically away for me, so this wouldn't solve the issue. [;)]

To explain the motivation better:

My project has (currently) about 40 levels. I imagined it would be easier to calculate offsets between several coordinate systems:

• the bounder's plan uses normal height null as reference;
• the architect's plan uses FFL as reference which is 34.8m above NHN;
• the brick mason's notes use the lower edge of the base plate as reference which is 42cm below FFL;
• I use the moisture barrier as reference of height which is 16.5mm below FFL since it is visible from the outside when I plan the modeling of the garden's surface;
• when controlling the surface elevation, I use moisture barrier plus 50cm since my surveyor's level device is approx 10cm high and needs a tripod;
• upper floor uses FFL plus 2,91m, attic adds some more height.

I know, it's just addition and subtraction in the range of -100 to +800. Not that difficult, especially for a computer engineer, isn't it?

However, oversight or miscalculation is difficult to correct when using armoured concrete. A good rule to avoid oversight is to keep it as simple as possible which means to translate all systems to _one_ coordinate system. I would prefer FFL.

Which leads to the world simply being 1m too high. [:)]