I was surprised that my numbers came out smaller than 100m too. That's why I don't bother coming up with theories until I see actual data.
You obviously have never checked the accuracy of your wheeling on grass, so your advice on how to improve accuracy, and your statements of how accurate it is if you just do it right, aren't worth much.
XC WannaBe wrote:
Our local USATF guy hosted an 8K race recently. The Garmin runners were getting 4.80 miles which means the course was probably 4.69 miles. I went out with my XC wheel the next day and got 4.68. I can see some margin of error, but we are talking over 6%. He is usually within 3% on the roads, but is blaming the error on this course on the lack of standardization of XC measurements. There is a local 3:0x:xx marathon that run this race in 27:0x and was calling it 5ish. Shame.
Yet again, it's cross country! You want exact "go to your local track."
dukerdog wrote:
I was surprised that my numbers came out smaller than 100m too. That's why I don't bother coming up with theories until I see actual data.
You obviously have never checked the accuracy of your wheeling on grass, so your advice on how to improve accuracy, and your statements of how accurate it is if you just do it right, aren't worth much.
Seems like I struck a nerve. How do you gather that I haven't varified the accuracy of our wheels on grass surfaces?
Is a Jones counter accurate on a course that is difficult to ride on a bike, such as a steep, rocky, single-track trail? I'm RD for a trail race, and we strive to provide accurate splits and overall distance. We've measured it numerous times with a survey wheel and GPS, and most people agree that the distances are "good enough" for an xc race. I'm curious if we would get a better reading with a Jones counter, especially since the route a bike would take is more sinuous than the route a runner could take because of roots, rocks, and tight switchbacks.
Surveyor Steve wrote:
Seems like I struck a nerve. How do you gather that I haven't varified the accuracy of our wheels on grass surfaces?
Because I asked you twice if you had, and twice you responded to me without answering that question.
If you have, great. I would genuinely be interested in seeing the data from those tests.
SowemT wrote:
Is a Jones counter accurate on a course that is difficult to ride on a bike, such as a steep, rocky, single-track trail?
It would be difficult to use a Jones Counter on such courses.
You could use a Jones Counter on the bicycle relevant parts, and your usual methods for the rest.
But I think what you are doing is probably the best way for that type of a course.
Sorry dukerdog-
I must have missed the first time you asked. Fool around/practice your technique and you will be able to dial it in much closer than you have so far. There is a science to measuring which you seem well aware of, but with some tools there is also an art.
Our data is simple. We test every tool before and after every project. When and if something doesn't comply we send it back if new, or dispose of it if used or beyond the warranty period. We do not use certain equipment in certain situations/conditions. For example with a wheel- if anything sticks to the wheel(usually high humidity or high moisture count in the ground material) or if the ground is actually wet we don't even attempt to measure.
How do you test a wheel before a project?
J.R. wrote:
It would be difficult to use a Jones Counter on such courses.
You could use a Jones Counter on the bicycle relevant parts, and your usual methods for the rest.
But I think what you are doing is probably the best way for that type of a course.
Thanks for the response. I've had a few people say it should be measured with a Jones Counter (including a USATF guy), but it never made sense to me given that you can't ride the same way you would run. We've contemplated using a bike for the downhill portions where you can roll the shortest route, but on switchbacks the bike would be taking a wide corner where runners could turn sharply. I think our method works, but I'd like to convince to others who swear by the Jones Counter.
Switchback - if you mean a "hair-pin" turn, I would suggest that you measure the turn with the widest possible radius to allow runners to minimize that amount that they need to slow down. Then it wouldn't make difference if you used a surveyor's wheel or calibrated JR Counter/bike (which I don't suggest either -as already mentioned).
:)
SowemT wrote:
I've had a few people say it should be measured with a Jones Counter (including a USATF guy)
Maybe he'll be glad to measure the course for you. :)
David Katz wrote:
I would suggest that you measure the turn with the widest possible radius
Do you usually measure in that manner?
I always measure, and run, the shortest possible route.
If the course was measured multiple times with a GPS, the persons doing those measurements were careful to follow the SPR, and the max difference among all those measurements was no more than say, 0.6%, then an average of those measurements is very likely to be within 0.3% of the true distance of the course, and probably a bit closer. I would doubt you could do any better on that type of course with a calibrated wheel or bicycle.
I'm not sure if there's any difference between a switchback and a hair-pin turn, but it's a Forest Service trail, so the sharp turns on steep hills are referred to as switchbacks. On a bike, you would have to take a very wide turn in order to make the corner. Some cyclists can't even make the turn without getting off their bike. A fast runner would probably round the corner wide to help maintain speed, but a slow runner could take the shortest route possible.
We maybe talking about two different things:
1. I refer to a "hairpin" turn as one that is on an open road or field where you create the turn. This is often done in road races as the method to be able to "nail" the distance desired. When a "hairpin" turn is created, cones delineate the inside parameter of the course. But, the actual measured line is 30 cm from the outer edge of the cones. Often with racewalking courses, the measurer will measure the shortest path to the cones creating an inaccurate course.
2. If you are mean a very tigh u-turn created by the terrain (trees, shrubs, etc.) either method will still work (but as mentioned - I still don't support the use of the wheel(s) as being very accurate.
The notion of the distance going up a steep hairpin is not so 'clear'. Yes, you can measure the shortest distance, but it is often pretty bad to run the shortest distance if it is very steep because the gradient is so steep on the inside. The road surface can also be rather slanted. In bike racing you usually go a bit more into the middle on the steepest turns.
One time trial up Mt Baldy I was passing a guy who starts several minutes ahead of me. As I caught him he tried to maintain my pace, which he did for a while. Then we got to the hairpin turn and it was so steep that I heard a 'thunk' behind; I think he went to the inside line a bit and was going so slowly that he could not maintain balance (the upper end of the switchbacks, where the road averages 10% gradient and on the insides of the turns is probably almost twice that.
By the way, they are using that road for an Alpe du Huez -type of finish at the Tour of California in May.
dukerdog wrote:
How do you test a wheel before a project?
Track Surface we follow the steel tape that is stretched on the straights. Just like we do on site plans for malls, factories, Field Turf, Golf Courses, etc.
That's what I did too of course. I'll try again with different pressures to see how much the readings change. But even if it works, I have to worry about a measuring method that relies on something so subjective as the measurer applying the correct amount of extra pressure. You'd be better off just using the weight of the wheel, getting 99m per 100, and then just applying that cal constant to the final measurement. As long as you're getting a consistent reading during calibration it doesn't matter what that reading is.
dukerdog wrote:
That's what I did too of course. I'll try again with different pressures to see how much the readings change. But even if it works, I have to worry about a measuring method that relies on something so subjective as the measurer applying the correct amount of extra pressure. You'd be better off just using the weight of the wheel, getting 99m per 100, and then just applying that cal constant to the final measurement. As long as you're getting a consistent reading during calibration it doesn't matter what that reading is.
Such is the life of a measurer that relies on a learned skill to hold, steer, and guide an instrument. I have the same feeling about a bike with a measuring device. You have NO control on the amount of pressure applied to the surface so you will surely have issues on soft surfaces that change in density. It also takes a skill to keep the front wheel steady and ride the best line. I'm sure I would entertain the idea of the bike if I had longer projects to deal with, but luckily I don't.
This is one aspect where the bike has an advantage; it applies a very steady pressure to the ground and is less affected by the unevenness of grass, which does not withstand the pressure of a 'loaded' bike.
dukerdog wrote:
That's what I did too of course. I'll try again with different pressures to see how much the readings change. But even if it works, I have to worry about a measuring method that relies on something so subjective as the measurer applying the correct amount of extra pressure. You'd be better off just using the weight of the wheel, getting 99m per 100, and then just applying that cal constant to the final measurement. As long as you're getting a consistent reading during calibration it doesn't matter what that reading is.
I think that the bike does have the advantage of applying a consistent pressure that is not controlled by the person doing the measurement. I'm not convinced though, that the large pressure the bike applies to the ground is an advantage.
But a practical consideration is that the people who manage the golf course are not going to be too happy to see somebody riding down their fairways on a bicycle. In many cases using a bike is not going to be an option.