AutoCAD Architecture 700,000,000 millimetres from home

Take a look at the image right/below (click the thumbnails if you want a closer view). This is an old file (from the 90’s) and displaying it in 3D with a conceptual shader revealed geometry falling apart. Posts that should be square had degraded to triangles, shelves were sloping and outlines were displaced from the shaded geometry.

At first I was perplexed but then found the problem. We draw in metric with one millimetre = one AutoCAD unit. The site, rather than building, plan was being used as an underlay and it used a datum which placed the store just over 700km from 0,0,0!

When you’re measuring in millimetres adding 700km results in some huge numbers and I suspect the system was just running out of numbers. Moving everything closer to home (0,0,0) sorted out the graphics.