I find it useful to use ARCGIS at very large scales. I use it to map features at the micrometer scale. So - at measuring unit of 1 centimeter this might be a scale of , 1:0.001
However at these scales its not possible to generate smooth curves - as vertices are deleted upon finishing the sketch. Seems that the vertices are "legal" but that they cannot be processed due to proximity! There appears to be a limit to how close vertices can be to each other at these scales. See example. The width of the image is 0.3mm or 300 microns and the line was a smooth curve of vertices - until it was finished - end result missing vertices.
I have tried setting up a map without coordinates and will custom coordinates with an origin of 0,0 etc. But get the same result at very large scales. Any thoughts appreciated.
That is pretty far outside of what ArcMap was designed for.
You may want to consider switching to AutoCAD. What is the benefit of mapping something that small
Agreed. It is really useful to be able to create layers of different data and interpretations - just like smaller scale maps. There are other ways of doing this but ARCGIS brings a lot of utility.