Measuring dirt roads

Measuring on Dirt Roads

I don’t see a lot of options here. There have been few studies done, and results differ. As Scott says, there’s no clear consensus on dirt road measurement.

One way to look at it is this:

1) Consider that a standard measuring tool is a standard bicycle calibrated on a standard road. Where I live a standard road is a road paved with asphalt or concrete. In other areas this may not be so.
2) Courses measured with standard tools will agree within varying tolerances. If the course is on ordinary roads we think the tolerance is about 1/1000. This approach and tolerance limit has served to support record-keeping.
3) On a dirt road the tolerance is likely to be different. How much? We don’t have a good idea yet, but it’s probably more than 1/1000. What should be done? Something? Nothing?

I lean toward doing nothing. Road running records on dirt roads are likely to be few, and if the few resulting record courses are checked by the standard method – as they were measured – they should have a similar “pass” rate as the paved ones.

It’s possible to require people who measure on dirt to set down a calibration course on dirt, but what kind of dirt? How does one find a representative stretch of dirt? Pavement surfaces will vary, but not nearly as much as dirt surfaces.

There was a time when all USA dirt surfaces had be measured by steel taping. This produced a few accurate courses, but it’s not known how many measurements were canceled because it was just too difficult to do.

My view is a relaxed one – use whatever paved calibration course you have and go out and measure whatever you want, wherever you want. Accuracy will not be as good as on pavement, but it is still way ahead of any other alternative. It will yield a course that is reasonably accurate, and provide the runners with an honest course.

What about records? What about the courses being found short on validation? To begin with, if I was assigned a validation ride, and the course had originally been measured using a steel tape, I’d plan on doing a bike measurement. I think this is generally understood to be the method of choice.

There’s a balance that needs to be struck. Dirt measurements may be less accurate than pavement, but not measuring at all is a bad choice. It’s a bad idea to make the measurement process more complicated and time-consuming than it already is.

This is a post I made to MNF a few years ago. It is the only time I have measured a substantial distance on a non-paved surface.

MNF#0653 7Aug2000

Steel Tape Measuring

It is Sunday morning and I am looking at my calculations of last
weekend's measuring for the Sound and Silence 10K. I am mystified at the
results. I used the Jones Counter to double check the sections of this route
that we had to measure by hand. There were three sections: 1247.0 meters,
543.7 meters and 1117.2 meters for a total of 4154.9 meters that would be
used on race day. The 1247.0 m. section is run twice. These three sections
each have different types of gravel surfaces so I was not going to spend the
time to lay out three more calibration courses since I knew we could measure
them more accurately by hand. My checks are as follows:

steel tape: ride 1: ride2:

1247.0 1245.3

543.7 543.1 543.0

1117.2 1116.7 1114.0

I did not included the SCPF for the rides as I wanted a direct
comparison. I would have expected the rides all to be longer but as you can
see they are all just the opposite. I am on my way back out there right now
to remeasure the 543.7 m. leg to satisfy myself that I'm not certifiably
crazy. If this route were completely paved I would have been done two weeks
ago.

Later:
I have to stop second guessing myself. We remeasured the 543.7 meter
leg and got........543.7 meters. So that is what it is. I am going to treat
the steel taped distances as %100 accurate and only apply the SCPF to the
bicycle measured parts.


I wouldn't steel tape that sort of distance again. I would do as Pete has suggested and simply meaure it by bike. It is WAY too much work to hand measure much over a few hundred meters.

Hmmmmm...that didn't format very well. I hope its clear that the Jones counter distances were always shorter but not by very much if I had included the SPF.

As well, the responses, if I remember correctly, suggested that the front wheel may be slipping in the gravel and therefore not turning fully as it would on a smooth paved surface. Sounded reasonable to me.

I measured a course (out and back) today that had a half mile stretch on dirt/gravel bike path, and for me, the biggest pain was that the one mile point was on the trail. How do you landmark such points: "Third big oak tree on the left past the two granite boulders"?

The 30 km I cite is the only measurement job I've turned down because of any uncertainty I had about a surface. I know, as Pete said, that our method produces the best measurements available but the thought of measuring 11 miles of dirt roads of various shades made me come unhinged a bit.

I'd be curious to see studies that compare different kinds of dirt surfaces to pavement/concrete. Do dirt surfaces make miles longer? Does it depend on the condition of the dirt surface?

Trying to describe where marks are on dirt roads is maddening Jim. Unless it's to a certified point, I'll step off marks to things that appear permanent and let it go at that.

Jim Gerweck raised the question of how to mark splits on a dirt road or trail. I recently encountered this problem and came up with the "whisker" or "stake chaser." They can be obtained from surveyor suppliers and come in many colors. They are essentially a 9" long grouping of plastic strands with a metal slot at the bottom for a 60d nail. It's driven into the ground about an inch with the nail providing solid anchoring deeper and the whiskers showing eight inches of vertical prominence. I do document them as best as I can, but at least they are a specific point to look for in relation to the documentation.

I paid $4.25 for 25 of them then obtained the nails at the hardware store for 6.5¢ each, pretty cost effective in my book.

I have not yet had the opportunity to check on their durability since the race against trail maintenance and traffic but they were fine for that race day.

Never heard of them, but sounds like a good tool. I have a turnaround point in a 15km that we run in January that's on a dirt road with nothing but horse farmland on either side. Might work for that, if the snow's not too deep.

Dirt trails brings up a second question, along with snaking paved roads in parks that have no curb. In theory they should be coned all the way down the inside of the curves. In practice we know the race directors just tell people to stay on the road.

Both conditions give a course that may be the correct lenth, but none of us would want it used for records.

We already have a system with two effective grades of certified course. Record eligible, or ineligible, because of altitude loss or Start, Finish separation, etc.

Its therefor strange that we only advertize one grade of certified. The certification number fails to tell the client or runner much about the quality of the course or record eligibility. Should there be two grades, A and B ?

The B should not be for bad measurements of length, but for quality of environmental conditions that affect the confidence in records set on the course. Grade A would be record eligible with curbed corners, run paved roads with all the other records eligibility requirements.

The second grade B, would be anything where the overall accuracy in length exceeds the standard for accuracy and repeatability, but the course it self, because of other environmental conditions, make the measurer or certifier less than confident that the course should be record eligible. For example poor surface conditions, off road trail, lack of defined curbs, ability for runners to short cut, or obvious inability to marshal or monitor course complacence.

I think measurer would be more comfortable being able to say to a RD that the overall measurement is on target but for this course I can only issue you a B level cert because .....

Most Race Directors understand that off road or dirt can be a problem and would be more happy to have a B level cert rather than nothing at all. They are often putting on a fun local event, or a training run. They want the course to be the right length with good splits but don’t expect any one to break any records.

I can think of several courses laid out in local parks that are exact in length, so long as the runner stays on tack. But the course winds around uncurbed corners or takes off on to foot paths.

Monitoring if a mid pack age group runner was really on the course, and not cutting corners is just about impossible. Maybe some of these should be considered as grade B courses because of the course environment.

The second problem is that Race Directors of local events are probably are not planning to have the timing systems in place that are required for a record to be validated. They would probably be relieved to know that no idiot is going to turn up and try to set a record at their event, when they have not planned for it. The B level course would warn people that it may contain off road or other issues.

I just did a cross country 5K. Put the counter on a mountin bike and callabrated on my 1/2 mile cert course. Did the course 3 times and all three counts were very close to dead on. The cross country runners were thrilled to run a 'real' 5K distance. I could never pull a cert on that course but the distance was right on, every turn defined by a natural barrier or obstical, and the results were repeatable.

Maybe this is a way for us to spread our measurement competence into other areas of the athlete universe. I have often done triathlons where the advertized distances were WAY off the mark. Where I am there are getting to be a lot of tri and du races. Should we get involved in measuring the bike and run segments of the events ?

How many people here have become involved in measuring un-certified events like off road races or triathlon courses, or doing certifcatons for just part of the event ?

Decades ago I contacted TriFed to see if they were interested in setting up a measurement/certification system for their sport. I was unable to find anyone who showed interest.

I just have to add this anecdote on measuring dirt.
It was my first solo attempt at measuring a race, the Danville Half Marathon, Danville VA. The RD was running along with me as I rode to show me the course, and as we hit the unpaved section I thought it looked VERY well maintained, freshly graded with roller compaction marks and signs new gravel had been recently added. At mile seven, I came around a bend on a steep (12%) downhill and could not avoid running over a rattlesnake crossing the path. I did not stop to take data as he was still moving, and would not be a relatively permanent feature.
Saturday morning, I rode it again to verify the distance. As I hit the gravel section, I noticed that construction equipment had been there that morning, and new gravel had been placed, but not rolled. I had to use the offset method to get around some of the equipment grading the road.
Needless to say, the measurements did not agree, so I had to try again. Saturday afternoon, the equipment had made it down to the start. All in all, I measured that stretch three times in 24 hours, and never rode the same surface twice.
I told this to the RD, and he then informed me that it was in the process of being paved, and would be complete in a week or two. Hmmm.
I had to go back to remeasure that stretch.
The paved distance came out a bit longer than the unpaved, I'll have to get my notes to compare the two and post the results.

I agree with those like Scott who are skeptical of courses measured on varying surfaces such as dirt. It would be fun to design and carry out a good comparison of results according to surface-- but a lot of this work has already been done, and has been written up in Measurement News. A major idea that I have come away with is: rougher surfaces tend to read shorter than expected rather than longer. This is a comforting finding and allows me to side with Pete in saying, just go ahead and measure it using your regular methods.
Bob Thurston