RunningAHEAD - Topic: Official race time vs. Garmin time (page 2)

Julia Sugarbaker

The Terminator

posted: 7/22/2008 at 4:49 PM

Consider also that you may have added some distance weaving around other runners or not taking the apex of turns.

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Chenille

posted: 7/22/2008 at 5:24 PM

Quote from jlynnbob on 7/21/2008 at 4:39 PM:

When they start asking for the Garmin time for my Boston Qualifier on the race application, I'll start using my Garmin over official race times/distances...

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Bonkin

posted: 7/22/2008 at 5:49 PM

Quote from backstretch on 7/22/2008 at 4:08 PM:

There are two ways the forerunner takes a reading once every second or once every 7 seconds.......I can't imagine that once every 7 seconds would be more accurate then once a second.

Really?

When it’s all said and done, will you have said more than you’ve done?

backstretch

posted: 7/22/2008 at 7:26 PM
modified: 7/22/2008 at 7:41 PM

Quote from Bonkin on 7/22/2008 at 5:49 PM:

Really?

http://www8.garmin.com/manuals/984_OwnersManual.pdf Your info from Wiki..mine from Garmin.....who to believe Big grin

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perfesserr

Imminent Catastrophe

posted: 7/22/2008 at 7:27 PM

You asked about TIME, not distance. So your watch should be accurate within a second so long as you press the buttons as you cross the start and finish lines. The accuracy of the race clock depends on whether you wear a chip and if the race puts timing mats at the start and finish (some only have mats at the finish) and the actual location of the mats (some mats are not exactly at the finish line). Here's my method: I always wear a watch and hack the time when I cross the start and finish lines. If the race is chip timed and has start and finish mats, I use the official (race) time. If it is not chip timed, or they don't use a start mat, I use my watch time. If the official time differs considerably from my watch time, and I know that I hacked the watch correctly, then I use my time. If you're really asking about distance, and it's a USATF certified course, then use their distance because the method that they use to measure a certified course is much more accurate than your GPS.

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Bonkin

posted: 7/23/2008 at 11:51 AM

Quote from backstretch on 7/22/2008 at 7:26 PM:

http://www8.garmin.com/manuals/984_OwnersManual.pdf Your info from Wiki..mine from Garmin.....who to believe

Did you happen to notice whose wiki it came from? Perhaps not. You said:

There are two ways the forerunner takes a reading once every second or once every 7 seconds

They said:

When the device is set to Smart Recording, course/track points are recorded whenever necessary. The device is constantly monitoring changes in direction, speed, and elevation, and captures a course/track point when it detects change. It could be every second if you're travelling fast on tight turns, or minutes if you're stopped or moving very, very slowly. Unless you're doing short short track activities or super fast downhill runs, Smart Recording is the most accurate and recommended recording setting.

I was just pointing out that your assumptions of how often it "takes a reading" were incorrect.

I can't imagine that once every 7 seconds would be more accurate then once a second.

I don't think it's more accurate either. But given how it works, at running speeds, it is not noticibly less accurate. If you were driving a car 60 miles per hour - perhaps we the discrepancy would be meaningful.

When it’s all said and done, will you have said more than you’ve done?

backstretch

posted: 7/23/2008 at 12:56 PM

Smart recording takes a reading once every seven seconds, It is why the battery will last 10hrs instead of the 3.5 hrs if it records every second. That is what I read and I'm not too concerned to go look it up and post it for you. If you are changing directions and whatnot, I guess it will register a reading but if you are continuing in the same direction at a steady pace, it's once evey 7 seconds.

"The drops of rain make a hole in the stone, not by violence, but by oft falling." - Lucretius

buck919

posted: 7/23/2008 at 1:21 PM

This whole discussion reminds me of another I was involved in on at a different forum. It had to do with a 1/2 marathon and a few runners (myself included) who had Garmin distances up to 0.5 miles longer than 13.1 and were arguing that the course was too long. The same counter agrguments were made (e.g. GPS isn't perfect, course is measured on the tangents, weaving, etc.) as those being made in this forum. Those with the Garmins, again, myself included, maintained that our units were never off by this much distance. Well, lo and behold, the Race Director happened upon the forum and concured that the course was long by 0.3 miles. http://www.runningroom.com/discussion/viewtopic.php?t=33108 I completely trusted my Garmin for time and distance before this race, and I trust it even more now! Lesson learned at this race? Be wary of a non-certified course!

kcam

posted: 7/23/2008 at 6:59 PM

Quote from backstretch on 7/23/2008 at 12:56 PM:

Smart recording takes a reading once every seven seconds, It is why the battery will last 10hrs instead of the 3.5 hrs if it records every second. That is what I read and I'm not too concerned to go look it up and post it for you. If you are changing directions and whatnot, I guess it will register a reading but if you are continuing in the same direction at a steady pace, it's once evey 7 seconds.

Smart recording or one-reading-a-second has little to no effect on battery life! It only affects how long an activity (or combination of activities) can be recorded before data begins to be overwritten. 1Sample/Second = 3.5 hrs, Smart Recording = unknown to me(but very, very long). You can run along in 1Sample/Sec mode and go for 7.0 hours but you'll only have the last 3.5 hours stored in memory. The first 3.5 would have been overwritten.

Doug B

posted: 7/25/2008 at 11:30 AM

Anyone who wants to understand this issue should strap on a Garmin, go for a run, come back home and connect it to their computer, upload the run to the Training Center software (free download from Garmin website), hit the export to Google Earth menu item (free download from Google), and view the run data overlayed on the satellite view. The satellite view is good enough to see the sidewalks and bikepaths. Now watch how many times the Garmin thinks you weaved into traffic. Or took a swim through the lake. Or did some other odd things. They are great tools. And probably only add 1% to your distance. Pretty damn close.

spaniel

Feeling the growl again

posted: 7/27/2008 at 12:52 AM

Quote from backstretch on 7/22/2008 at 4:08 PM:

There are two ways the forerunner takes a reading once every second or once every 7 seconds.......I can't imagine that once every 7 seconds would be more accurate then once a second.

Each time it takes a measurement, there is error. It may be in front of, behind, to the left, or right of your actual location. The more measurements, the more the chance for errors. The front/back ones may cancel each other out but the left/right ones will not....it will compute your course as if you were continuously weaving left and right. If you are running in a straight line, the more points it takes, the more weaving it thinks you are doing. If you run straight roads like I do, max out the "smoothing" function as most weaves it perceives are really errors. If you run a lot of curves, set it down some as more of them are likely to be real. I have seen the pictures of where people map the actual course they ran onto a satellite view....often it is very enlightening to see just how wrong the little unit can be from time to time, especially in cities.

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backstretch

posted: 7/27/2008 at 2:23 PM

Quote from backstretch on 7/20/2008 at 6:08 PM:

I've found the Garmin extremely accurate............if it doesn't lose satellite contact. I used google maps to chart a course, google showed it to be 33.17 km. When I ran the course and wore my Garmin it showed 33.16 km.

Amazing how the above workedout, with all that weaving. Big grin

"The drops of rain make a hole in the stone, not by violence, but by oft falling." - Lucretius

spaniel

Feeling the growl again

posted: 7/27/2008 at 6:53 PM

Of course that begs the question, how accurate is google maps? I've measured several relatively long property lines with google maps and again by hand -- both with a laser rangefinder and a wheel. It's decent, but not perfect.

"If you want to be a bad a$s, then do what a bad a$s does. There's your pep talk for today. Go Run." -- Slo_Hand

I am spaniel - Crusher of Treadmills

Quid

Running God

posted: 8/3/2008 at 3:10 AM

For those who have great curiosity, take a look at this site. It points out the many errors including the ionospheric interference that is one of the largest error factors, as well as multipath (seen in cities with the signal bouncing all over the walls of buildings. http://edu-observatory.org/gps/gps_accuracy.html I had my GPS ( nice Garmin ) taken from my car in a smash and grab - I have not found the need to replace it. It was lot's of fun to plot the path of travel whenever I traveled. But it is only so good. One other point - the 10 or 20 foot circle around yout GPS is actually a sphere - we are in 3 space. So not only does the unit think you are zigging and zagging it can appear to have you hopping up in the air and below the ground as part of the "path traveled" - something harder to see on Google Maps - unless you tilt the point of view. B Big grin

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Daddyo

Go Pre!

posted: 8/3/2008 at 12:43 PM

This question should never have been asked.

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Official race time vs. Garmin time (Read 1212 times)