Question about Garmin forerunner 405

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louiskie

2008-08-12 3:26 PM

Extreme Veteran

1942

In front of computer when typing this.

Subject: Question about Garmin forerunner 405

Hi all. OK, so I just a cool new toy (forerunner 405) and have been playing with it non-stop (including on the bike downhill, which is a bad idea). Anyway, the question I have is this. If I am in the woods, Garmin keeps the satellite signal and seems to map the distance correctly (its a trail of known distance and at the end the distance makes sense), but the immediate "speed" readout is all outa whack. For instance, I will be "running" 4mph one second and then a few second later, while not changing anything in my pace, will be running 7mph because now I am out of the woods. In the open it is very accurate (almost identical to my cateye bike computer) but in the woods the speed seems off but distance seems accurate. I don't really understand how that would work. Does it have some background software to correct? Am I just confused and it really isn't tracking correctly? I suppose I could call Garmin as well but would rather get opinions from you guys, plus I wanted to share the news of my new toy. :-)

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LazyMarathoner

2008-08-12 3:29 PM

in reply to: #1598243

Pro

4608

Brooklyn, NY

Subject: RE: Question about Garmin forerunner 405

I have the same issue in NYC. When I run along the river, especially out on a pier, the pacing will be very off - sometimes it says I'm running a 13-min pace when I'm really doing about 8-min - but the distance I ran is always accurate. I've reconfirmed with Google Earth and gmap pedometer. I'm not sure why it does this or how it manages to keep accurate distance but not pace, so I too am curious!

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louiskie

2008-08-12 3:32 PM

in reply to: #1598265

Extreme Veteran

1942

In front of computer when typing this.

Subject: RE: Question about Garmin forerunner 405

LazyMarathoner - 2008-08-12 4:29 PM I have the same issue in NYC. When I run along the river, especially out on a pier, the pacing will be very off - sometimes it says I'm running a 13-min pace when I'm really doing about 8-min - but the distance I ran is always accurate. I've reconfirmed with Google Earth and gmap pedometer. I'm not sure why it does this or how it manages to keep accurate distance but not pace, so I too am curious!

Yeah, it is odd. As long as the distance is accurate I am cool with it. It just seems really odd though. Anywya, hopefully someone smart will tell us what the deal is :-)

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Winston63

2008-08-12 4:26 PM

in reply to: #1598243

Regular

134

SF Bay Area, CA

Subject: RE: Question about Garmin forerunner 405

I have a 305, and the instantaneous pacing is always off a bit. The average is right on. Also, on my 305 you can set the "smoothing" of pacing, Less, more, most. Something like that. Can you do that on the 405?

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WaterDog66

2008-08-12 5:03 PM

in reply to: #1598243

Champion

5345

Carlsbad, California

Subject: RE: Question about Garmin forerunner 405

The "Spot Pace" given out by GPS devices in general is not always going to be the most accurate mostly because the distance between each poll is small enough that the % Error of GPS becomes signficant.

What complicates things is that Garmin uses it's frame of reference to calculate not only distance change, but elevation change.

What I do is what most of my marathoner friends do: Ignore the "Spot Pace" and use the "Average Pace" over the last "Lap" with Auto-Lap enabled and set to 1 mile. (So you get your average pace over the portion of the current mile/lap you happen to be running)

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Gritty

2008-08-12 10:25 PM

in reply to: #1598243

Expert

721

Chenequa WI

Subject: RE: Question about Garmin forerunner 405

As mentioned, all GPS watches will have a problem with instantaneous pacing. The Garmin 405 is very good, but the only way to get instant pacing is with the footpod. I use the pod with the GPS on. When used like this, I get the instant pace, run cadence and the route is recorded with the GPS.

Edited by Gritty 2008-08-12 10:26 PM

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ballyard7

2008-08-13 12:51 PM

in reply to: #1598243

Expert

939

Tulsa

Subject: RE: Question about Garmin forerunner 405

Come on people, it's just simple math lol. The GPS works by taking data points every so many seconds or milliseconds. It takes the last point and the current point and determines the distance between them. It knows how much time elasped because it takes a data point every so often. Anyway time/distance = pace. Thats the instant pace.

If you are in the woods or a place where it can't get the optimal gps signal it sometimes doesn't know how far you went. So in essence it misses that data point. So it calculates your pace based on the previous distance with more time = slower pace. Something like that. And so on for the faster pace. Thats why overall it works out to be correct.

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goran007

2008-09-15 10:56 AM

in reply to: #1598243