Gene, Was there a link or attachment? I don't appear to have it. Completely guessing at the content, I am assuming you may have essentially a standing wave in a (nearly) lossless transmission. The laser EDM may be a bit different. The beam has moderate divergence to assist in aiming. Not all the energy hits the reflecort (at large distances) nor does the reflected energy all make it back. Further the detector would detect the travelling wave not the composite electric (or magnetic field). I would expect the transmitted and reflected beams to have little interaction. Since the beam is modulated, there may be some dispersion based on variation of index of refraction with wavelength. However, the bandwidth of the modulation is very small. However, I am not up to refreshing my waves and transmission line knowledge. I got the limiting specs of some EDMs and they made my point. Unlike interferometry in vacuum, it is not reasonable to expect errors on the order of wavelength.
--- On Mon, 1/31/11, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: [USMA:49723] Re: [SI] A mole hill into Himalayas To: "U.S. Metric Association" <[email protected]> Date: Monday, January 31, 2011, 4:37 PM John, Here is another comment on the errors of optical devices; There is a teaching film showing wave crests moving to the right while the envelopes of group pulses simultaneously move to the left; demonstrating the potential for errors in laser surveying devices. The configuration for this demonstration is a chain of discrete capacitors and inductors. I leave it to our readers to discover which of these are connected in series and which, are connected in parallel. I showed this film to my students of "Transmission Lines, Fields, and Waves" in a routine undergraduate course at the University of Illinois (in Urbana, IL). Gene. ... >---- Original message ---- >>Date: Sun, 30 Jan 2011 14:00:50 -0800 (PST) >>From: "John M. Steele" <[email protected]> >>Subject: [USMA:49700] Re: [SI] A mole hill into Himalayas >>To: "U.S. Metric Association" <[email protected]> >> >> I did further checking, including looking at Leica >> specs. Those numbers like 1.5 mm + 2 mm/km are not >> worst case specs, they are standard deviations. >> Statistically, we know there is reasonable chance of >> individual measurements having errors out to 2 or 3 >> standard deviations, rarely even more. >> ...
