10K was short, OK to conservatively convert?

Misleading Or No wrote:

Had a 10K this morning that was one of my big goal races for the year. The race director had to change the course and it ended up being approximately 9K (0.6 miles short).

Most short courses are actually only short on the GPS. If there are lots of tall buildings or trees, it will register short on the GPS due to multipath error. It has to be wheeled.

Did you wheel the course to verify the distance? Maybe you are actually in 33 shape?

ekw wrote:

Misleading Or No wrote:

Well, my post got cut off somehow.

LOL. I bet you're using wireless internet to post? need I say more? Oh, the irony.

BTW, to respond to the comment about Honda's +/- 2.5%:

2.5% of a 10k (6.2 miles) is 0.155 of a mile. The GPS from the OP measured it to be 0.55 miles short which is a difference of .395 of a mile. So go out and drive the course and see what happens because as I said, driving the route in the car would be MORE accurate than your GPS watch... It is not the most accurate, but it certainly is more accurate than GPS.

Wow, impressive how many times you can miserably fail in one post.

First, your "bet" was so wrong it's comical. It's obvious from his cutoff posts that he was trying to use a symbol like "less than" or "greater than"... which causes the post to truncate here at LetsRun. Do you always bet on things you are completely wrong about?

Secondly, do you not comprehend that the course was ACTUALLY way short? Your car vs GPS explanation makes it sound like you think the course was close to accurate. The OP explained it wasn't, and even the race director had said it would be short. Your reading comprehension is struggling, dude.

You make me laugh wrote:

Secondly, do you not comprehend that the course was ACTUALLY way short? .

Not that dude you are responding to, but I've run 10ks through the trees where the GPS read 5.1miles at the end. I rode my MTB on the same course later and it measured 6.2 exactly with calibrated cat-eye device.

Also in his defense, Seb's dad would measure routes by car and drive behind him. Car's are pretty accurate.

You make me laugh wrote:

Wow, impressive how many times you can miserably fail in one post.

First, your "bet" was so wrong it's comical. It's obvious from his cutoff posts that he was trying to use a symbol like "less than" or "greater than"... which causes the post to truncate here at LetsRun. Do you always bet on things you are completely wrong about?

Secondly, do you not comprehend that the course was ACTUALLY way short? Your car vs GPS explanation makes it sound like you think the course was close to accurate. The OP explained it wasn't, and even the race director had said it would be short. Your reading comprehension is struggling, dude.

The post cut-off thing was a joke, chill out.

I do not instantly comprehend that the course was ACTUALLY way short due to a lack of credible information. I am giving the benefit of the doubt to the entire organization that put the event together vs one person who used one gps watch. Pretty reasonable, yes? For a race director to be off in his 6.2mile distance by over 12% is absurd. Also, I do not believe the OP when he said the race director said the course would be short. Because if a race director was going to say that to his runners, either he was offer up the information as to HOW short it would be, or one of the runners would ASK him. I read just fine however I do not take everything at face value. Use a bit a common sense to figure out of a story makes sense.

you are still not getting it wrote:

You are still assuming that it is easy to drive the shortest possible route in your car. Unless you go out there at 4 AM, that is probably not going to be remotely possible. And if you do it then, you will likely be pulled over on suspicion of DUI if a cop sees you.

I do agree that driving all of the tangents would be the most accurate but not practically reasonable in the real world on open roads. That being said, driving tangents vs no do so would be negligible (I'd garner to guess under 1/10th of a mile) over the distance of 6.2 miles through a "normal" course. Obviously, the more turns there are the more inaccurate that the driving-non-tangent test would be.

My conclusion, in the point of all of my posts to this thread are:

DRIVE THE COURSE. It is amazingly fast and easy to do and it nets you an additional set of results to compare your one and only other test: a gps! If the driving test is also anywhere near half a mile short, than maybe we can re-discuss the OP's original conversion questions. However, if he does the driving test and the course only comes out 1/10th of a mile short, what say you now? I'd say to so the driving test 1 or two more times and if he REALLY wants to get an accurate PR conversion, go by a wheel and walk the course!

ekw wrote:

I do not instantly comprehend that the course was ACTUALLY way short due to a lack of credible information. I am giving the benefit of the doubt to the entire organization that put the event together vs one person who used one gps watch. Pretty reasonable, yes? For a race director to be off in his 6.2mile distance by over 12% is absurd. Also, I do not believe the OP when he said the race director said the course would be short. Because if a race director was going to say that to his runners, either he was offer up the information as to HOW short it would be, or one of the runners would ASK him. I read just fine however I do not take everything at face value. Use a bit a common sense to figure out of a story makes sense.

Common sense?!?!!

We're talking about a 37 minute 10k runner running a 33:xx. Use your common sense...

Cronje wrote:

Common sense?!?!!

We're talking about a 37 minute 10k runner running a 33:xx. Use your common sense...

According to the OP he is a 39:xx 10ker. So either way he is making HUGE jumps to a new PR. a 2 minute PR at that level seems just as outlandish as a 6 minute PR... his story has many many holes.

row row rowbury your boat wrote:

My first question is, "How the hell could Google Earth be more accurate than a wheel?" Seriously, I am not being a d*ck, how is that possible?

On damp grass, wheels slide. On gravel or poorly cut grass, wheels skip and jump. Even on a track, try to walk without wobbling.

Go into google earth and CAREFULLY measure a track. I just did. I got 399.32m, and that's with 200m of it being a turn (which are difficult to plot points on). Over a 10,000m, that's 15.5m off, or just less than 0.01 mile. If you can get that accurate with a wheel, I'd be absolutely amazed. Again, this is google earth with the user manually plotting the points, not some program like mapmyrun that simply "follows road"...that can be off by a ton.

way short is possible wrote:

You make me laugh wrote:

Secondly, do you not comprehend that the course was ACTUALLY way short? .

Not that dude you are responding to, but I've run 10ks through the trees where the GPS read 5.1miles at the end. I rode my MTB on the same course later and it measured 6.2 exactly with calibrated cat-eye device.

Also in his defense, Seb's dad would measure routes by car and drive behind him. Car's are pretty accurate.

Peter's car was definitely out as his son also ran 10 milers in 45 mins.

ekw wrote:

Cronje wrote:

Common sense?!?!!

We're talking about a 37 minute 10k runner running a 33:xx. Use your common sense...

According to the OP he is a 39:xx 10ker. So either way he is making HUGE jumps to a new PR. a 2 minute PR at that level seems just as outlandish as a 6 minute PR... his story has many many holes.

Geez just give up already. A 2 minute PR is not as outlandish as a 6 minute PR.

ekw wrote:

Personally, I use :

http://www.runningmap.com/beta/

It is easy to use and as accurate as I could tell. I've tested it by creating routes that match known high-profile races included the boston marathon, Beach to beacon 10k, NYC half marathon, etc. All the routes were incredibly accurate down to what I could tell where just a matter of 10 or less feet off.

You realize that's impossible right? The short course protection factor would add 10 meters to a 10k, 21 meters to a half marathon... so you should be at least 21 meters long. Even the best measurers don't come within 10 feet of the true distance for a 21 km course. If you got within 10 feet it was dumb luck. Maybe that's why "D.Katz," the dude who measured the Olympic marathon course, disagrees with everything you wrote.

ekw wrote:

Cronje wrote:

Common sense?!?!!

We're talking about a 37 minute 10k runner running a 33:xx. Use your common sense...

According to the OP he is a 39:xx 10ker. So either way he is making HUGE jumps to a new PR. a 2 minute PR at that level seems just as outlandish as a 6 minute PR... his story has many many holes.

Where are the holes in this story?

1. Race director says course is short

2. OP runs 4 minutes faster than expected

3. OP's watch says it's 0.55 miles short

And you still don't believe it's short! You are delusional!!

agc5k wrote:

Same thing happened to me in base phase last summer. Did a 10k in 34:50. Was like "no way bro," checked my watch and it said 5.83 miles. Converted it out to 37:00. Old pr was 38:24. So I put it down as a pr but an asterisk next to it.

Asterisk or no asterisk, you didn't run a 10k that day.

A simple google search will tell you that:

a) gps is not accurate, even with clear sky on a perfect day

b) car odometer is not accurate

c) bike is the standardized way to measure a course. not your everyday commute bay, a special one, calibrated. even with rough terrain it is the standard.

justsomeoldcoach wrote:

A simple google search will tell you that:

a) gps is not accurate, even with clear sky on a perfect day

b) car odometer is not accurate

c) bike is the standardized way to measure a course. not your everyday commute bay, a special one, calibrated. even with rough terrain it is the standard.

That's not the argument.

Since not everyone has a Jones Counter, a bicycle, and a clear/open course at their disposal, we're debating other techniques of measurement. And for those who read "bike" and thought using a Cateye would suffice, it's not accurate enough either.

This thread is making my head spin.

My opinion- regardless of the reason(s) that the course was short, one should not try rationalize a PR from it. Stuff happens, move on.

In regards to the accuracy of the various methods of measurement mentioned, I would rate them in the following order based on my experience (most accurate to least accurate):

1. Calibrated Riegel-Jones Bicycle Method by an experience road course measurer cutting all the tangents within 30cm of turns and cones.That's the world standard - The only method accepted for Certification around the world. Also, steel taping an entire course cutting tangents. This has been done in the far east with a number of races in the past.

2. Google Earth Measurement. This works well as previously mentioned if you zoom in and CAREFULLY measure the tangents. I can come up withing 10-15 over a 10km course when compared to the bicycle method. Many top course measurers will use this method to map out the course prior to the actual bike measurement. It also helps eliminating gross areas as well as giving a good idea where the splits will be located.

3. CALIBRATED Measuring Wheel. This sounds like it should be rated #2 but most users wouldn't be able to walk the tangents without wobble. Plus you need to walk at a speed of less the 20 minutes per mile. The hard wheel increases bouncing and loss of ground contact. Also, most users never calibrate the wheel. OK for short training distances on a smooth surface.

4. GPS mounted on bicycle - cutting the tangents. This method has increased accuracy over a runner wearing one on their wrist due to the fact that you have a better chance following the tangents. But there still could be problems with blockage from buildings. I remember measuring one course in NYC with several other measurers where the gps gave us a reading over nearly 0.10 mile different from the jones counter over one mile! We were surrounding by tall buildings.

5. Other online mapping programs.- Not bad, but I have found it sometimes difficult to measure tangents.

6. GPS on the wrist. . A good training tool. - Let's stop right there....please!

7. Bike Cyclometers. Not bad but they usually only read within increments of 0.1 miles. Set it to km for better accuracy.

6. Auto. This shouldn't even be on the list. Vehicles are for transporting people and goods, not for measuring anything!

As previously mentioned, vehicles can't measure the tangents which could be very significant on some courses. Add this to tire pressure changes due to temperature + other stuff and there's enough reason to eliminate it.

During my early days of measuring I found that cars would come up short when compared to my bike measurements.

ooops, Auto should be #8! I was inserting some others and forgot to re-number. And to add to the last sentence on cars. I found that a course measured by a car at 5 miles only measured 4.75-4.8 miles when measured by the bike method.

The vast majority of the error in methods 2-6 in David's list is due to operator error. The person doing the measurement doesn't know what they are doing. Most people think that following the SPR (shortest possible route) means staying on the inside edges of turns, but there is more to it than that. It's not hard to learn how to follow the SPR, it's just that most people running a race wearing a GPS, and most people measuring with a wheel, don't do it.

A calibrated bicycle is a good bit more accurate than any of the devices used in methods 2-6, but that's only part of the reason measuring a course following the USATF procedure is much more accurate than methods 2-6.

Google Earth is officially more accurate than a wheel, my mind is blown!

To be fair, I never even thought about the zoom factor on the websites. When I use them, I am making a generalized route and start the first 2-3 miles zoomed in hitting the tangents, then get bored and use the "follow the road" method. Lol, lazy, but good enough for a daily run. These explanations make good sense.

For the sake of the GPS watch then, (I know we obviously shouldn't use it for accuracy) are we on correct assumption that it will always measure short? Is there an anomaly that could cause it to be long?