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Reply to "Laser distance meter for cal course layout?"

About 15 years ago I laid out a 1/2 mile cert course on the road outside my house.
The road is dead straight, level and just over 1/2 mile long. I decided to do a 1/2 mile cert course.

The idea being that any error in a cert course would be multiplied as one scaled up to the race distance. If a 1/2 mile cert course was as much as 6" out that would only end up with a three feet error at 5K.

Additionally riding that distance on the cert course would be very similar to riding on the race course. One rides differently when looking down than up into the distance.

And any fractional error from the discreet digits on a Jones counter would be negligible on that distance.

For years I have wanted to validate my 1/2 mile cert course. However redoing the two steel tape measurements by the same method would only confirm any error in method or any error in the length of my tape.

Over the years asked various survivors working on my street if they would help.

I have had various answers from my equipment cant shoot that distance, to hire us and book a job, to sod off.

However today two very nice gents were surveying for a house sale a few houses away. I can spot a shiny new high end survey rig, and knew this was good crew to ask. They were happy to help.

After confirming their equipment would have no problem with 1/2 a mile, I went out by bicycle and placed cones over the marks.
Then lent the bike to his man who biked out to hold the reflector pole. (Accurate pole with bubble level). This was shot from their high end TDR system. Not a GPS based system, so no GPS errors.

I was flabbergasted when they told me the result.

With no prompting or suggestion from me on what I expected, they reported 2,640.17 feet.

It took three people the best part of a day to do the orignal measurements. Took a good tape loaded with a spring gauge, sturdy nails at each point, and a table of corrections for the error or correction at each nail. 2 inches off in 1/2 mile.

Will spend the rest of the day feeling rather validated.
Last edited by jamesm
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