Here's a simple maths problem. Take a circle of radius 10. This radius could be any unit of measurement; millimetres,inches,light years,baby steps. To find the area of this circle, you apply the formula:
Therefore the area of our circle is 3.14159 x (10²) = 314.159
Seems simple enough?
Not according to Revit
Draw a filled region using a circle of radius 10.
Firstly, do this using metric units (mm & mm²) and you get:
Now do this in imperial units (decimal in & in²) and you get:
The metric figure is 99.98% accurate, the imperial a little closer. Big deal you may say, and in most cases you'd be correct, certainly in a small example like this. But what if I take this circle and make it bigger, then I extrude it to make some 3D geometry, then I copy this around many times, then I want to know the volume of these elements? Small errors start to compound into more significant overall errors
pi is a constant. Revit knows this is a circle. So why the discrepancy?