RE: glass scales and tempeature

In terms of high accuarcy CAM, I'm WAY OUT OF MY EXPERTISE, but I had an interesting thought, which is likely well known by real experts.... I was wondering if digital indicators which provide data output port connections (such as SPC), might be used in small "CNC like manners". The thought is that because the indicators read down to 0.00005", if these indicators were correctly placed in the setup and provided the necessary feedback, it seems that high accuarcy and minimal temperature effect (based on their placement) might be something that could be acheived. Obviously their range is limitied.

Has anyone heard of closing the loop from indicators such as these to the motion components? What sort of data, and what speed is the data provided from these indicators? I've had the idea that it might be interesting if the feedback for CNC could be switched from one source to another and back as a part of the program.... Is this done?

David Howland