Last week Jean-Francois Delasalle sent this to approximately thirty measurers. He is conducting a survey. The preliminary results are interesting.

With his permission I am posting it here.

Results will be posted here on March 14.

No names will be posted in the results. Your answer will be anonymous.

Here is the question:

During a recent meeting with several measurers we had a discussion about the following small theoretical problem :

"You measure the distance between two nails hammered in the road with a steel tape by two German measurers . You find 463,86 meters . The temperature is 4°Celsius.

What is the length of this calibration course?"
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Original Post

Results of Temperature Correction Survey

The following people responded to the survey.

Bob Baumel
Guido Bros
Bernie Conway
Woody Cornwell
John DeHaye
Michael Franke
Bill Glauz
David Harriman
Justin Kuo
Tom McBrayer
Mark Neal
Gene Newman
Pete Riegel
Duane Russell
Matthew Studholme
Bob Wemer
Jay Wight

All but one ultimately submitted the correct answer of 463.77 meters, based on a coefficient of linear expansion of 0.0000116/C. The one different answer was 463.79 meters. This was based on a coefficient of linear expansion of 0.0000093/C, which was the value printed on his personal tape. I counted this as correct. Two initially submitted incorrect answers but later checked their work and resubmitted correct answers.

During the survey nobody was informed whether their answer was right or wrong.
Which proves the Steel Tape Method instructions are very clear, and easy to understand.

Pete, thanks for managing this exercise!
It also makes a good case for "check and double check."
It seems as though our FS are on top of their game!
Practice makes perfect. Too bad we didn't have newbies in the survey.

I am looking forward to seeing whatever Jean-Francois Delasalle makes of this additional data. His group was less experienced and less successful.
COMBINED SUMMARY OF THE TEMPERATURE CORRECTION STUDY BY JEAN-FRANCOIS DELASALLE

Greetings to all,

AB = 463.86 m as measured at 4C. The corrected length is 463.77 m. (463.86 x Correction Factor). The correction factor is less than 1 when the temperature is less than 20C.

Correction factor = 1 + (.0000116 x (T° -20)) = 0.99814 for 4C.

Why? The tape contracts when temperature is less than 20C. When it is read at point B it indicates a figure greater than the true AB. (the reading at 20c will be less than the reading at 4C).

See the figure below to aid understanding.

This figure appeared in Measurement News, August 1986

46 responses were received from 14 countries. 40 were correct (463.77 m) and 6 incorrect (463.94 m). 8 people changed their answer after thinking about it. 7 gave a correct revised answer and one gave an incorrect revised answer.

Responses were received from the following countries: USA 17, France 15. One each from Australia, Brazil, Canada, Great Britain, italy, Morocco, Poland, South Africa, Switzerland and Turkey.

Among the 28 non-USA responses were AIMS/IAAF approved measurers. (18 grade A and 13 grade B, and 18 national level measurers).

Recorded errors included 2 from “A” measurers, 2 from “B” measurers and 2 from national level measurers

Thanks to all who participated in this study.

Jean Francois

Translated by Pete Riegel
This topic raises a question. When determining "the temperature" is it preferable to use the ambiant temperature or the road surface temperature?

I notice that some measurers utilize an infrared device that reads the road temperature. The road surface temp is often much hotter than the air.

The device is slick but I'm certain my tape is not as hot as the road surface. A steel fin conducts heat well, but also dissipates it rapidly. Therefore I've been using the ambiant temperature when adjusting the measured tape length. Is that OK to do? Any thoughts or advice on road surface vs ambiant temperature in course measurment work?