garmin gps inaccuracy

Don't know about the 110, but I've read that with the release of the 220 and beyond, they went to a new and less robust chip. My 220 is a mess. I wish my old 305 hadn't died. It was duct taped and super glued to keep it working, but it remained accurate as Hell 'till the end.

The track is long. Not unusual.

disagree. the watch must be faulty. look for the 100% accuracy guarantee in the little booklet that came with the watch. i think you even may be entitled to punitive damages when it's off by that much.

pacingblows wrote:

Does anyone else have a garmin that fluctuates a little? Today I ran 20 times around the high school track and it said .54?? WTF?? I mean shouldn't it say .50? Unless I really ran .04 extra? I tried to hug the line as much as possible hmmm don't get it...

Running a marathon in a couple months.. Will be close to a BQ.. Scared to death my watch will screw me... Any help?

P.S It's a forerunner 110

GPS isn't very accurate when you are running around a track. They are much more accurate when you run in a straight line, like on roads.

I ran a 10.000m on a track and the garmin measured 10.6k. And yes, I didn't run an extra lap. Similar for 5.000m.

I ran a 10k on a 2.5 loop course and the garmin measured 10.12k.

So, I would guess that the pace can be off by a couple of seconds even when you run fairly straight lines in the countryside.

With buildings or hills it might be off constantly because of reflection of the signal. Don't get stressed out, just run.

If available put on the 1 second mode.

gps wrote:

pacingblows wrote:

Does anyone else have a garmin that fluctuates a little? Today I ran 20 times around the high school track and it said .54?? WTF?? I mean shouldn't it say .50? Unless I really ran .04 extra? I tried to hug the line as much as possible hmmm don't get it...

Running a marathon in a couple months.. Will be close to a BQ.. Scared to death my watch will screw me... Any help?

P.S It's a forerunner 110

GPS isn't very accurate when you are running around a track. They are much more accurate when you run in a straight line, like on roads.

Not true.

How is the OP determining the length of the run?

Two problems:

1. the radio in the device isn't accurate

2. These workout apps are nothing like wayz. They don't "know" your location like wayz. They just log GPS points. That's not the same thing.

Is there a Garmin that might be a little more accurate? What I don't like bout the forerunner 110 is, is that it doesn't tell u your current pace, it averages the mile. When the miles are off during the marathon your screwed.

garmin 610 wrote:

I ran a 10.000m on a track and the garmin measured 10.6k. And yes, I didn't run an extra lap. Similar for 5.000m.

I ran a 10k on a 2.5 loop course and the garmin measured 10.12k.

So, I would guess that the pace can be off by a couple of seconds even when you run fairly straight lines in the countryside.

With buildings or hills it might be off constantly because of reflection of the signal. Don't get stressed out, just run.

If available put on the 1 second mode.

Were you sure the loop was exactly 2.5? And did you run the tangents?

Even if it isn't entirely accurate, 0.12 is only 1% off.

If you're betting everything on a watch's accuracy you're in a heap of trouble. You're really going to have to practice the pace on a known distance to get the feel.

The long and short of it is while most Garmin (and other GPS) watches are reasonably accurate, there's a wealth of things that can through them off. They may be dead-on on one course, off by a few percentage points on another.

Small GPS antenna's like in any watch are prone to interference. Say your track goes around a football field and there's big lights, a stadium, etc, on one or more sides. That can interfere with the triangulation necessary to make GPS work.

Is your marathon in a big city? Through a wooded area? Going through a wind farm? Going through a neighborhood with a bunch of those invisible fences? You get the picture.

My 410 claims that I stop dead for a few minutes, then run over 60MPH for 1/4 mile when I go by a local country club's tennis courts. Similar situation when on a bike ride I do, same course varies between 32.5 and 34.1 miles. Some days I apparently fly ET style over some houses according to the tracks.

In any case why the hell are you using a GPS on a tracK? You lost? Don't know how long the track is? Geez. Practice your damn pace by checking your splits like normal people.

pacingsucks wrote:

Is there a Garmin that might be a little more accurate? What I don't like bout the forerunner 110 is, is that it doesn't tell u your current pace, it averages the mile. When the miles are off during the marathon your screwed.

Current pace is very unstable on all watches.

I think for a marathon your average pace and pace/mile is more important?

Drive a few miles of open road (no buildings/tall trees around) and check it with your odometer. Then compare it with your watch after running the exact same distance.

My 620 sometimes screws up when I run near tall buildings/trees I think it has to do with the satellite signals bouncing around.

My feeling is moreso that the track length is bunk. To check that, you'd need to get one of those wheely dealios. But if your open road test works, you've proved your watch is accurate.

It's really not that hard to make an accurate GPS watch (coming from a background in electrical engineering here). You would have some basic calculations regarding time of flight, triangulation. It's like saying your home calculator can't do square roots properly, and it's because texas instruments made a faulty calculator. It just doesn't seem likely. These calculations to determine position, and by using a timer, speed, have been replicated in millions of GPS devices. I bet the calculation is even standardized, and the Garmin engineers just copy and paste the same code between devices. Inaccurate GPS results would be the #1 thing they'd test.

Piano_Man87 wrote:

Drive a few miles of open road (no buildings/tall trees around) and check it with your odometer. Then compare it with your watch after running the exact same distance.

My feeling is moreso that the track length is bunk. To check that, you'd need to get one of those wheely dealios. But if your open road test works, you've proved your watch is accurate.

This is not necessary. You can measure it from behind your computer:

(use the satellite mode and straight line).

I measured my local track this way: exactly 400m.

You people need to understand that gps watches are not accurate on tracks because they draw tangents every few seconds around the corners.

Thanks.

I like seeing you post. Wish I took time to know you when I was in W-S.

Jckckf wrote:

You people need to understand that gps watches are not accurate on tracks because they draw tangents every few seconds around the corners.

Wrong on so many levels. GPS watches are never accurate. Doesn't matter the location. It's the way the technology is, not a brand/device issue.

OP: there are many situations where using a GPS watch is beneficial. Yours is not the case.

I think sometimes it's dead on. Went on a run and it was exactly the distance I mapped out.

There is no GPS watch that can measure precise distance when running around the track. Even the latest Garmin's which have built-in accelometer is off by few meters after several laps.

This is not a watch problem but a GPS technology specifics. Firstly GPS accuracy in ideal conditions (i.e. clear sky, sunny day, no tall buildings that reflect satellite signal) is around +/- 3 meters for civil use.

Military has access to accuracy of +/-0.5 meters

pacingblows wrote:

Does anyone else have a garmin that fluctuates a little? Today I ran 20 times around the high school track and it said .54?? WTF?? I mean shouldn't it say .50? Unless I really ran .04 extra? I tried to hug the line as much as possible hmmm don't get it...

Why should it say .5 after 20 laps? Shouldn't is say 8,000 meters, or the equivalent in whatever unit of measure you're using (4.97 miles, 8 Kilometers, 26,246.7 feet, etc.)? In what unit of measure would .5 be the correct reading after 20 laps?

qw wrote:

This is not a watch problem but a GPS technology specifics. Firstly GPS accuracy in ideal conditions (i.e. clear sky, sunny day, no tall buildings that reflect satellite signal) is around +/- 3 meters for civil use.

Military has access to accuracy of +/-0.5 meters

There are plenty of available GPS units that are extremely accurate, they just don't fit in a watch.

Think about what you're comparing. Even a basic car or trek GPS has about 10 times the antenna surface of a GPS watch.The military signalling units are even larger. Not "big" by any standard, but much, much bigger than a watch. When you consider that it's antenna + algorithm = accuracy the watches do pretty good under the circumstances.