I run on trails at altitude so I am debating getting a Garmin - do they work OK? Good idea or bad? Thx

they work great, at altitude and at sea level. I bet you'll discover that your trail distances are shorter than you think. My "8 mile" trail run turned out to be 6.7 miles.

Long story short, GPS signals won't penetrate a tree canopy that well, so the unit won't be able to track distance that well, so your distance/pace won't be too accurate. If anything, distance measured will be short.

So, if you're buying it to nail down your distance thru the forest, save your $.

Now, on open road/trail, works great.

Oops, missed a sublety: if you're running on non-forested trails with a clear view of the sky, works great!

I spent the last weekend in the high mountains of Northern California. One of the days i decided to break out my Garmin, despite knowing that they seem to struggle in the mtns, and especially on single track trails that are on rolling terrain. Running on a section of the Pacific Crest Trail that had a fair # of climbs but was often open and not covered by trees... the watch seemed to be well off the mark. Miles that i felt were at least in the 8 minute range were timed/measured at 10:00 pace. Given that I'm probably in 33-something shape for 10k and run most of my aerobic runs at 7:00 pace or quicker at home, I'm pretty certain that the watch was well off the actual distances up there. It's too bad that they can't make a watch that actually measures accurately in the areas where you need them the most.

handheld GPS units can be very inaccurate when it comes to calculating altitude, so if you are wondering about vertical delta on your runs, you might be disappointed. I use GPS on my bike every ride, and unless I do an 'altitude correction' off known altitude data, it's a mess. I have hill repeats that should be identical obviously, and the vertical data is all over the place. But for distance it's very good.

I've only run on open roads in altitude and never had problems with reception or losing signal. When I look at the data afterwards at the training center site, it has been fairly accurate with the elevation change.

if you know about what pace you're going why do you need a garmin?

I'll never understand some people's obsession with recording their runs to the tenth or even the hundredth of a mile.

colorado runner wrote:

if you know about what pace you're going why do you need a garmin?

I'll never understand some people's obsession with recording their runs to the tenth or even the hundredth of a mile.

I agree with what you're saying. I only bought the watch to measure loops and courses for workouts in my hometown. I'm a coach, so it'll be handy for some of these types of purposes. As for measuring exact distances, it's never been a big deal for me.. but I was curious how well the watch would work in this environment. The O.P. was asking about purchasing the watch for trail runs, so i gave him my feedback.

gps is great when used with mapping software to see where you ran. i have discovered great trails by looking at runs and finding that i could take a left and get to whole new area.

obviously you can do this with a trail map if you know what you are doing, but it is a lot easier when you see your exact path mapped on top of the trails.

note that much of the software that does this mapping is crap and you need something that uses maps from openstreetmap. for the mac, rubiTrack is the best one I have found.

The Garmin doesn't work very well on trails because of switchbacks. It draws a striaght line every 5 or so seconds so if you do alot of back and forth furing that time, it just cuts the tangent. This can add up on some trails.

Who cares how far a trail is anyway. Time + effort = training stimulus. Miles are not as good a measure of volume as minutes. Not all miles are created equal.

the garmin doesnt work that way. it always takes a reading every second, and then decides which ones to keep. so if you have 5 points all in a straight line, at similar pace it doesnt need all 5, so dumps some of the middle ones.

on the 305 you had the option of storing all of them, or having it do this "smart" storage. on the 310xt i didnt see that option (but didnt look hard).

it can still cut corners, but it's not just a simple 5 second sampling.

i looked a trail run i did this morning on the 310xt and it did a pretty decent job on the switchbacks - on the sharpest turns it was keeping points every second, but on straighter parts only a point every 5 seconds or so.

They don't measure up and down distances.

Love the Garmin for trail running. Hey there is no right or wrong answer here...but I like the tracking of altitude and distances. It's not an obsession...but for the numbers oriented folks out there, Garmins are fun.

Set one of the custom fields to to show you GPS accuracy. If it consistently stays below, say, 70 and it tells you that you ran a ten minute mile, then you ran a ten minute mile, no matter what it feels like. If not, it is blocked by the terrain. Frankly as long as it's below 100, that ten minute mile is going to be a lot closer to ten than it is to seven regardless.

in reality, the up/down is pretty negligable to the overall distance

if you climb 100 meters in a mile, you are only covering an extra 3 meters (1612 vs 1609) - so it's a .2% error for a 6.2% grade.

if you climb 400 meters in a mile (which really is a pretty ugly run with a grade of 24.85%) you covered an extra 49 meters (1658 vs 1609) - so a 2.95% error.

if this is critical there is desktop software that will handle the true distance, including elevation changes.

garmin s on most areas are 100 % right. We use the 405 for our 1/4s if you mark it out everyweek and the same spot is 1/4 and same is 1/2 its right.I run over 5k races and it goes to 3.1 at the mark.If you are on a new course you might want to go over it 2xs .Long short of it like a wheel bumps are rough areas can make it off (with gps its other things).Run over the same course 3-4 xs and you keep get the same distance its right.

If you want better accuracy and are willing to carry an extra couple ounces there are the Garmin handhelds. My Vista HCx (which I use for hiking, not running) holds its signal very well even in thick forest, and it has a barometric altimeter that gives accurate elevation data. It's fun to keep track of how many thousands of feet you gain and lose in a day, or if you're charging up a hill you can go back an see your peak rate of ascent. Trivial information, but fun.

I have used mine several times in the mountains around Colorado, at Leadville, Pikes Peak, etc. It seems to be both accurate (based on distance marks using actual measurements) as well as consistent. I am not a freak about being exact, but it has been a useful tool.

Yeah my 405 is awesome even when running in the trees. I'm not sure where the negativity is coming from for these devices. The better signal you get the more accurate it will be. If you're running in and out of areas heavily covered with trees it will still get your distance right but your pace may vary 5-10 seconds as your running as it adjusts. One thing to remember is the pace that you see on the watch when you're running is what it estimates your mile or whatever you have your lap set to be. It is NOT your current pace. That messed me up at first. There is not a thing negative to say about the Garmin 405 especially at the cost of approx $225 dollars. If you run everyday and calculate it's use over 2 years you spend more money buying a can of soda from the machine. For me it was a no brainer.