🚀 go-pugleaf

In article <HAGERMAN.92Oct5161957@rx7.ece.cmu.edu>, hagerman@ece.cmu.edu (John Hagerman) writes:
|> In article <1992Oct5.154211.21663@ecrc.de> micha@ecrc.de (Micha Meier) writes:
|> > 
|> > Although we can make a circle as precise as we want, I think we
|> > cannot make a really precise straight line - every straight line is
|> > made from another one or from a tool that has been made using some
|> > older straight lines ..............Although we have precise 
|> > instruments and tools, we can only make better and better lines 
|> > but IMHO there is no process to create a straight line directly. 
|> 
|> How about laser milling ? 

   Laser milling usually involves moving a laser head around on the 
   straight lines of a machine...which gets you back to square one. 
   As someone else recently posted you can use a laser to calibrate
   a machine or setup but generating a line is something different. 
   I've never used a laser over a long distance but it seems that it
   would be affected by mirage or 'seeing' the same way a long distance 
   shooter or telescope user is. 

   I seem to recall that the Mormans used long trays of water when
   laying out the pitch of their irrigation systems and that it was
   remarkably accurate over a long distance. Some early astronomers
   also used trays of water to test their flats. A chalk line works
   well as does a plumb line but like most (all?) generated figures,  
   circles included, some error is always present. With some types 
   of setups one can rotate the figure 180 degres in a plane or around
   an axis and regenerate or remeasure the line in an attempt to cancel
   out some error. Usually one is forced to say that this line is
   straight in this plane or space to within some value at some level  
   of confidence, as one has to account for 'four dimensional' error 
   where each time it is measured you get a different answer.   

   John Ongtooguk (johno@sdd.hp.com)