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Measuring Wheel Use

matthewstudholmematthewstudholmeCertifier
I have recently received an inquiry from a professional land surveyor concerning the use of a measuring wheel (calibrated on a certified calibration course) instead of a calibrated bicycle. The proposed measuring wheel is of the type shown in this link:

http://www.keson.com/products/...easuring-Wheels.aspx

The surveyor said in an e-mail to me: "Measuring wheels are essentially the same or greater accuracy than the bicycle method since there is no air pressure involved. Consistency would be improved."

Are such measuring wheels acceptable for course measurement if used by a professional land surveyor? If the e-mail was from someone other than a surveyor, I would not be asking this question. If the question had come from a regular measurer my response would have been "no" as it's more difficult to keep a straight line when walking a wheel than riding a bicycle.
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alanjonesalanjonesMember
Everyone on this forum should be aware of the pioneering work that Ted Corbitt did over 40 years ago. In his monograph (http://www.usatf.org/about/committees/LongDistanceRunning/RoadRunningTechnicalCouncil/history/corbitt.pdf) Ted goes into great detail about different methods of measuring and proceeds to tell what is wrong with each on -- except the calibrated bicycle method. I suggest you point your surveyor contact to Ted's document. He makes too many points about the problem with the calibrated surveyor wheel to reproduce here.

Alan
AdminAdminMember
The primary concern with using a measuring wheel to measure race courses is the difficulty in following the SPR, right?
If someone can measure a road course with a calibrated measuring wheel twice and have the measurements come within 0.08% of each other, I would be fairly confident the measurement was accurate.
That 0.08% check is the also the only way we know a new measurer has done a good job of following the SPR on his calibrated bicycle.

That being said, you might recommend to him to measure a short course around his neighborhood to make sure he can actually do two measurements to within 0.08%.
Last edited by Admin
matthewstudholmematthewstudholmeCertifier
In Ted Corbitt's document that Alan directed us towards, the stated accuracy of a surveyor's measuring wheel is 5 yards per mile when pushed slowly ( 2 miles/ hour) and operated carefully, which translates to 0.28%. The accuracy of the bicycle method as we know is better than 0.08% or 4.2 feet per mile between measurements. I was surprised to see the 5 yards per mile number but it's in line with the Keson measuring wheel website that I cited earlier in this thread which states an accuracy of 99.7% (or 0.3% between measurements) on a flat, even track. Many road courses are not flat, even tracks, so presumably the 0.3% for measuring wheels is as good as it gets, particularly if Keson's statement on their website is true that their measuring wheels are "the best in the world".
AdminAdminMember
I'm sure Keson's accuracy number is for an uncalibrated measurement. That's the number most people buying a measuring wheel would want to know.

Both Pete and I have measured tracks with a calibrated measuring wheel and for both of us our two measurements were well within 0.08%, and the measurements were very close to what they should have been for a 400-meter track. When it is very easy to follow the SPR, like on a track, I think you can get very accurate measurements with a calibrated wheel.

We assume (for good reason I think) that it is much more difficult to follow the SPR on a road course with a measuring wheel than with a bike. But I don't think there is a lot of experimental evidence to confirm this.
D davidkatzMember
I have a great deal of experience in using a measuring wheel in my early days (mid 70's) before I hooked up with Ted and the AAU National Standards Committee and "saw the light".
My observations:
1. a measuring wheel tends to lose surface contact more the the bike method. The solid wheel tends to bounce more when it hits debris in the road.
2. greater difficulty measuring the SPR especially on roadways with vehicles.
3. Fatigue. Try hold that handle steady with one hand for several miles. I had always been told to go at 20 minutes/mile or slower. Try hold the wheel straight with one hand for at least an hour....not fun

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