Garmin 405 not measuring correctly?

My God, you are insufferable. I took it to the track just to mess with it as I was running on the track anyway. I wasn't USING it for anything - just let it run whilerunning on the track. I do quite a few of my 10-11 mile easy runs on the track to get off the roads. Jesus!

Hey guys,

I just bought a Forerunner 205 refurbed cuz its cheaper. What are the best settings to make it the most accurate?

Ive read that the only thing you can change is to make it record data every second. Anything else?

Also, is there a way for it to tell me the pace of each mile I run? I thought it had to do with the Auto Lap feature, but when i turn it on, it only beeps telling me that one mile has passed, without the time of that mile.

Thanks!

Logic wrote:

The truth is: What kind of COMPLETE IDIOT uses a Garmin on a track and then has enough spare time on his hands to analyze why a mile doesn't come out quite right on a metric track?

Probably the same type of TOTAL MORON who would wear a Garmin or a HRM to a race or would record and report every split in a road race as if there would be any genuine utility in bothering. These are usually the same MAJOR DUNCES who make a practice of sweating details well before they ever master the basics.

So I ran 44 laps on the track yesterday (99m shy of 11 miles since it was a meter track) and let my Garmin run and just hit the lap timer every 1600m. 1.04 for the first 1600m, 1.05 for the next several, 1.06 for a few and then it read as much as 1.08 late in the run. .01 is 16m so you are looking at errors in the 80m+ range. The entire 44 laps was measured at 11.66. Looking at the Google Earth mapped result, it is patentluy obvious why it makes so much error on the track and not other places. It isn't just a matter of drawing a series of straight lines to define a curve, it is that a left to right error in pinpointing your spot on the earth at each reasing makes a huge difference when you are running a curve and very little difference when running a long straight road. A front to back error makes no difference on a straight line so long as you are ahead of the previous reading each time. The Garmin tended to place me several meters onto the infield during the turn on most laps. I am not sure why the pinpointing error almost always tended to be to the inside and not the outside of the turn.

The other day I was returning from a run and thought about this thread. I decided to try my own experiment based off what someone suggested here.

I picked out a long straight stretch of parking lot about 250 feet long. I walked it 3 times with my normal stride, my ForeRunner on my left wrist. The distances came out to 252, 249, and 250 feet.

Then I walked it while holding left wrist against my chest. The distances were 249, 250, and 250 feet.

You may take that for whatever it is worth. I doubt it will change the mind of anyone here. However I did notice one thing about my stride that I had never thought about before: When walking, each wrist stays almost perfectly level with the opposite foot. Each arm stays parallel to the opposite leg. Walk yourself and see what I mean. When your leg moves forward, your arm moves forward. When your leg "moves backward", so does your arm and wrist. Yes, I know it's obvious but consider what else that means:

I put "moves backward" in quotes becuase the fact is, your legs do NOT ever really "move backward". Not relative to the ground.. So wouldn't that mean the your wrists are doing the same?

In other words, it should be impossible to get any reading behind a previous one when walking forward, regardless of speed. Your wrists, like your legs, never move backwards relative to the ground.

do the math wrote:

Probably the same type of TOTAL MORON who would wear a Garmin or a HRM to a race or would record and report every split in a road race as if there would be any genuine utility in bothering. These are usually the same MAJOR DUNCES who make a practice of sweating details well before they ever master the basics.

There actually is utility in wearing a Garmin in a race. I've run more than one race/marathon that either had no mile splits or - even worse - incorrectly marked ones. This is a particular problem in longer races in which it can be difficult to settle into the proper pace early on. Just a couple of seconds per mile adds up to a couple of minutes ahead/behind where you want to be in a marathon. When you are so fresh, so early in the race, running completely rested and tapered for the first time in months, it can be difficult to reconcile how your body feels with what the watch says.

Last year I ran the Pocono marathon and was settling into the right pace when suddenly mile 3 came out as over 20 seconds faster than goal pace. I was all set to back off a little bit when I took a look at the Garmin and realized they'd marked it dramatically wrong. So I didn't make any adjustments and it turned out to be the right decision.

I beleive if the track has a curb or not can effect the distance of one lap.and where you run in the lane will obviously effect distance. also it looks like as you got more tired from your run you drifted slightly to the outside lane. not surprisingly when doing so many laps. you get sick of the roads so decided to run on the track eh. mmm. do you have one leg shorter than the other? thats like being sick of snow and moving to the north pole!

This so quite ridiculous.

Track = flat and soft rubber. Roads = hilly, crowned, and concrete (the roads are concrete, not asphault, in this town).

Where you run in a lane on the track doesn't cause a 100m+ discrepency per mile (you'd have some crazy lane staggers if that was true). All you have to do is look at the map generated by the track marks and see what happens. The GPS makes a several meter left to right error in pinpointing your spot on the globe. On a turn these are crucial. the GPs sees you as running the turn several meters into the infield. Someone posted a link to a photo of the GPS tracks on a track.

Use Garmin Training Center and then view your route in Google Earth and you can easily see what happens. Running on straight linear running paths, the GPS also makes left to right placement errors, but that usually generates a track that is more or less parallel to what you are actually running, so there is little distance difference. Not so on a curve.

What makes you think that Garmin calculates distance traveled simply by connecting the dots? I'm going to guess that the PhD's at Garmin are familiar with the concept of curve fitting.

dukerdog wrote:

What makes you think that Garmin calculates distance traveled simply by connecting the dots? I'm going to guess that the PhD's at Garmin are familiar with the concept of curve fitting.

Because that is exactly what it does. It doesn't matter how fmailiar they are with the concept, that is all the GPS can do with the data it receives. It isn't a problem of mathematical knowledge, it is a problem of the device capability. All a GPS can do is tell you where you are on the globe at a given time (with a bit less than pefect accuracy). Everything else has to be guessed at. It has no way of knowing you are running a curve. How could it receive data telling it that? Have you ever generated a track map of your run? You'll see quite clearly that this is what it does. All it can do is look for where the unit is every 4-5 seconds, plot it, then plot the next point, then measure the distance between the two points. How would it know if you are running a curve.

All of this has been talked about quite extensively on the Garmin boards with Garmin reps posting.

I BET IF YOU WORE IT ON THE LEFT WRIST IT WOULD MEASURE SHORTER THAN ON THE RIGHT WRIST.... TRY THAT ONE BRIAN.

While the outcome may be pleasing to you, you can't know any alternative outcome so there's no basis for saying that it was truly the "right decision." Your experiment of one lacks a control, I have no logical, factual basis to refute it as you have none to support it. There is no realistic basis for drawing a meaningful conclusion from such data. My finding is that analyzing such details to that degree is overstating their realistic importance. The fact that you were sweating a possible 20 second/mile discrepancy on a road course is telling. It shouldn't make or break your race unless you let it accrue to something like 2:00+ off per 10K.

A LOT of people stop trying new things because they become comfortable in a pedestrian routine and whatever small, regular gains it may yield. I look at a lot of mass-consumption training plans and it seems to me that too many of the people who follow them end up under-trained and over-tapered and, go figure, they end up not being able to run "longer races" successfully by feel. This may or may not be the case with you, since it is a multivariable study and 2:39 marathon PR is not conclusively either your absolute best or less than your absolute best. Plus a 1400'+ drop is ridiculous, certainly when starting below 2000' and with no significant climbing at all. What do splits even mean on such a circus course? It is great that you can plunk down a load of dough and get a gadget that will safeguard you from doing anything that would possibly be beyond the scope of what your training will allow. I can't begrudge anyone for doing that, it's very smart. On the other hand, and this is a general comment (like others made above) and not in any way personal, a lot of people end up unnecessarily limiting themselves too much in the name of "being smart."

[quote]PXC1990 wrote:

Hey guys,

Also, is there a way for it to tell me the pace of each mile I run? I thought it had to do with the Auto Lap feature, but when i turn it on, it only beeps telling me that one mile has passed, without the time of that mile.

quote]

There is an Auto Split feature that will record your time at every mile or whatever it is set for.

I was not happy with my 205 because of the inaccuracy wearing it on my wrist. It was constantly losing the signal.(probably my big head) I strapped it on the back of a hat and set the two auto features for every mile and I just got used to counting the beeps. Not very efficient as a watch but I run a lot of trails and different courses so it gave me a more accurate way to measure my runs.

It was a nice toy but the battery died about a year ago and I just let it go for about six months and gave it away.

Sure I can. I've encountered the alternative many, many times, in many, many marathons. I have years of going out too hard and blowing me telling me that it was the right decision.

It's a simple matter of information. Without the Garmin I would have been put to a decision: Do I slow down from what is obviously far too fast of a mile? Do I not trust the mile split? Would the wrong decision have destroyed my marathon? Unlikely. Would it have negatively affected it - quite likely. But either way, the tool eliminated the possibility of a decision based upon incorrect information.

Race day is not the day to try new things. Practice is. If you are unable to hold marathon goal pace for, long stretches in practice, it is not going to magically happen when the gun goes off. I've seen too many deluded people buy into that and pay the price.

5:43 / mile (which is what that particular split said) is not a pace I have ever come close to holding even racing a half-marathon, much less a marathon.

And a lot of people end up taking all the discipline and knowledge that they learned in training and throwing it out the window on race day, only to pay a heavy price in the last 10k of the marathon. I've done it myself.

There are no miracles on race day.

dukerdog wrote:

What makes you think that Garmin calculates distance traveled simply by connecting the dots? I'm going to guess that the PhD's at Garmin are familiar with the concept of curve fitting.

Brian wrote:

Because that is exactly what it does. It doesn't matter how fmailiar they are with the concept, that is all the GPS can do with the data it receives. It isn't a problem of mathematical knowledge, it is a problem of the device capability. All a GPS can do is tell you where you are on the globe at a given time (with a bit less than pefect accuracy). Everything else has to be guessed at. It has no way of knowing you are running a curve. How could it receive data telling it that? Have you ever generated a track map of your run? You'll see quite clearly that this is what it does. All it can do is look for where the unit is every 4-5 seconds, plot it, then plot the next point, then measure the distance between the two points.

That would be all it could do if its processing power was as limited as yours. Fortunately, its microprocessor has a bit more ooomph, and is capable of retrieving the last 20 data points from memory, calculating a curve fit of that data, calculating the length of that curve fit, and reporting the results to you. It's an amazing world Brian, where devices you carry around every day are capable of performing mathematics beyond the 4th-grade level.

Well, I believe that you believe that you can know that. However, there is not only one alternative. Also, physiological variables actually change from one marathon build-up to the next. At least they should. Accumulated aerobic development, to name a big one, unless it's really not that significant in this case. That alone could certainly allow what previously had been "blowing me" (interesting phrasing, even for this site) pace to be perfectly reasonable in a subsequent race.

Or do you wait to see what the next mile and/or 5km marker indicates instead of getting in a panic over a single mile split? It's splitting hairs, mere rationalization. The subsequent mile or 5km marker would have probably yielded the same insight, as well. Unless it was a total crap race with really randomly misplaced markers all over the place in which case anyone who relies on mile markers for their racing didn't do their homework.

Strawman. I said nothing about changing routine on race day, specifically. In fact, the term "routine" should have indicated otherwise.

So, even with firm knowledge of that fact, you didn't trust your preparation?

Granted and I did note that the first maybe 5 miles of that course drop very little compared with the middle miles. I was talking about overall. Look at about any race report people post online, they routinely contain splits for every mile as if there's any subtle clue to be found within the hallowed data. If you fall apart, especially in a marathon, you usually know it without even needing to look at a watch. Same deal if you have too much left at the end.

Then they are wrong and need to address that fallacy and shortcoming in their training.

Wow, I hope this defeatist attitude doesn't rub off on too many others reading this. I hope people take cues from people like Bill Rodgers and Steve Jones rather than Joe Downer the cliff-diver.

It's a matter of knowing vs guessing. You would apparently choose to wait a mile and find out if you were right or not, assuming they didn't screw that one up too. I would choose to know know. I don't see any virtue in guessing when you can know. One of us is rationalizing, that's for sure.

You spoke of trying new things. Since we were speaking of race day, what else am I to infer? And if you are not speaking about race day, it's not the rather narrow topic of discussion I was responding to when I mentioned wearing the Garmin in a marathon..

My preparation? Completely. My sense of pace when I'm fresh and tapered for the first time in months? Not so much. Sometimes it's right, sometimes it's wrong. I can dial in a pace easily in training, watch or no watch. I can do that day after day for months. But when I am fresh and tapered, it's far too easy for mile times to feel 20 seconds slower than they are. I am far from alone in that regard.

What good does that do you? Sure you know, only by then its too late. The time to make the adjustments is not when you fall apart. It's when you feel like a million bucks. When your goal pace seems too easy. Knowing the pace you are holding helps that.

There were no miracles for Rodgers or Jones either. They achieved their times by incredible hard work and incredible talent. Neither of them was surprised by their PRs. Neither of them ran paces that they didn't expect to be able to hold based on training.

dukerdog wrote:

dukerdog wrote:

That would be all it could do if its processing power was as limited as yours. Fortunately, its microprocessor has a bit more ooomph, and is capable of retrieving the last 20 data points from memory, calculating a curve fit of that data, calculating the length of that curve fit, and reporting the results to you. It's an amazing world Brian, where devices you carry around every day are capable of performing mathematics beyond the 4th-grade level.

You presume there are PhD's level mathematicians and programmers at Garmin. Sure the processors are quite capable, but if the programmers have a 4th-grade level math capability, the processors will perform 4th-grade math. If you factor in fixed bit length registers, and poor error management, could even be a lot worse than 4th-grade math.

Mr. Ray wrote:

You presume there are PhD's level mathematicians and programmers at Garmin. Sure the processors are quite capable, but if the programmers have a 4th-grade level math capability, the processors will perform 4th-grade math. If you factor in fixed bit length registers, and poor error management, could even be a lot worse than 4th-grade math.

I feel certain there are some very smart people at Garmin. The level of complexity they have to deal with in processing the data they get from the satellites in order to determine absolute position is far beyond that needed to do a simple curve fit, or even more advanced signal processing, to determine distance traveled. People think the satellites just "tell" the device where it is. Of course there is a lot more to it than that.