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EDM for second measurement of a calibration course
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Picture of Mark Neal
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Certification of a calibration course requires two measurements of the course, with the course length established as the average of the two measurements.
Should we allow one of these two measurements to be performed with an electronic distance meter, while the other is measured by steel tape? This would allow people to get familiar with these devices while still protecting against the dangers of relying on a new, unproven technology.
 
Posts: 939 | Location: Rochester, MI | Registered: 13 April 2006Reply With QuoteReport This Post
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I'm confused by your question. Isn't EDM measurement allowed already? I didn't think of EDM as a "new, unproven technology", but as a good way to put down an accurate cal course. At least when the terrain isn't too rolling. Measuring it twice (I think) with EDM would involve doing two independent setups of the device. Straighten me out if I'm wrong.
 
Posts: 515 | Location: Washington, DC | Registered: 16 November 2004Reply With QuoteReport This Post
Picture of Mark Neal
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Maybe I'm mistaken. I thought you needed to be licensed to use the equipment for use of an EDM to be OK.
 
Posts: 939 | Location: Rochester, MI | Registered: 13 April 2006Reply With QuoteReport This Post
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Maybe someone can help us out here. I wouldn't know how to use it personally without being shown, and I've usually thought of this as something to ask a surveyor to do as a favor or something. What restrictions, if any, are there on using an edm? I certified a cal course measured with edm, it was sent to me by Tom Riegel. But then he's a surveyor and I didn't think there was any question about his ability to use it accurately.
 
Posts: 515 | Location: Washington, DC | Registered: 16 November 2004Reply With QuoteReport This Post
Picture of Pete Riegel
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The problem with using electronic distance measuring equipment (EDM) lies not in the equipment but in ourselves. We certifiers are supposed to review the work of others. This requires us to have a decent understanding of the equipment used in the measurement. In the not-too-distant past the only EDM available was Total Station, a theodolite (surveyor’s transit) device which incorporated the electronics required to shoot a laser beam to a distant target reflector, receive back the reflected signal, and calculate the distance to the reflector. It incorporated an “optical plummet” in some cases, to eliminate the need for a plumb bob, used to center the instrument over the ground point.

I have little knowledge of the modern, cheap EDM rigs. I am not qualified to judge the quality of measurements produced by such instruments, thus cannot act as a certifier for those people who may choose to use them. I suspect I am not alone in this.

Steel tapes may not be high-tech, but they are understood by all of us certifiers. That’s why they are the standard we use.

Considering that I can lay out a calibration course in about a half hour with a steel tape, I can’t see that our adherence to steel-taping is causing anyone serious inconvenience.
 
Posts: 1747 | Location: Columbus, Ohio, USA | Registered: 23 October 2004Reply With QuoteReport This Post
Picture of Mark Neal
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I agree with what you say Pete, but that's why I suggested using the EDM only for the second measurement. The second measurement is required primarily to make sure something wasn't done incorrectly on the first measurement. If an EDM measurement was within an inch or so of the 1st taped measurement, then you can be pretty confident both were done correctly. If it's not, then you'd need to do a second taped measurement.
 
Posts: 939 | Location: Rochester, MI | Registered: 13 April 2006Reply With QuoteReport This Post
Picture of Justin Kuo
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Mark,

Measurers and Certifiers are innovative and will continue to seek new ideas as technology changes. For now, I would encourage you to use the Laser Measurement device along with the steel tape measurement. Continue to make the two steel tape measurements. As you suggested, using the Laser Measurement device would be great way to check that you did not miss counting a tape segment. That may replace using the a bicycle counter as check mechanism.

Continue the discussion on what you observe with the Laser Measurement device. As you refine the technique and methods, it will gain greater acceptance and may eventually be used as the primary measurement device.

Just an aside, the Leica Disto that I believe you are using, is used as part of the LASAM distance measurement device for measuring long throws in track & field events. Measurements are to made the nearer centimeter but the LASAM is much more accurate than that. Last summer, I tested the LASAM against a total station on a 100 meter straight section of track and found the measurements comparable. You won't find much info about the LASAM. The $6000 device was developed, built and sold by Dick Norman. I believe Gill is now selling the same device for a third of that price.

Thank you. -- Justin
 
Posts: 175 | Location: Brookline, MA | Registered: 24 October 2004Reply With QuoteReport This Post
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