12

Garmin dead zones (Read 204 times)


delicate flower

    Does anyone have any spots on your running routes where your Garmin (or whatever GPS watch) just seems to go haywire with your paces?  I have two spots in particular where the Garmin consistently goes into "WTF mode" when I run through there.  I look down at my watch while keeping a steady effort, and the pace goes from 8:30, to 8:40, to 8:55, all the way up over 10:00.  This goes on for about a half mile, then the pace gets back to normal.  There is a fair bit of tree cover in these spots, but I run through places with just as much tree cover and no issues.  I don't worry too much about it since I'm sure I get very fast readings from time to time as well (pretty sure I'm not actually hitting a 4:15 pace) and it all evens itself out in the end.  Still, I'm just wondering if this happens to anyone else.

     

    I use "current lap pace" and use one mile laps.  I have a 610 but this also happened with the 410 that I recently replaced.  Seems like a satellite issue more than a watch issue.

    roboknee.

      There is a fair bit of tree cover in these spots, but I run through places with just as much tree cover and no issues.  ....

       

      I use "current lap pace" and use one mile laps.  I have a 610 but this also happened with the 410 that I recently replaced.  Seems like a satellite issue more than a watch issue.

       

      Yes, this is unfortunately common and related to increased signal attenuation and increased multipath in these higher clutter areas.  The Forerunner 10, IMHO, does a much better job of filtering these false pace changes in heavy tree cover than does the 610 or any other of the earlier watches (when using "current pace").

       

      That being said, if you are using "lap pace" (which is what I think you mean, not "current pace") these effects should be GREATLY diminished unless you just happen to be in the first 200 meters or so of the new lap when you hit the tree cover.  Lap pace is just the average pace taken from the point where the last lap event occurred so after a quarter of a mile or so it is effectively a very heavy low pass filter and its output doesn't move around very much at all after that point even if you make real and significant pace changes.

      - Joe

      all running goals are under review by the executive committee.

        No coverage issues with my Garmin 110, as I live in the sticks with wide-open spaces, but somewhere on my long run the other day I apparently hit a top speed of 35 mph . . .


        day after day sameness

          The pace being all over the place is really a symptom.  The cause is the GPS track not accurately following your path due to signal loss or distortion from multipath issues caused by the layout of the area.  You actually covered, say 1/2 mile in 4:15, but the device thinks you've covered 1/3 mile due to it getting a bad track point -- so the calculated pace jumps up, or down if the device thinks your went longer due to its tracking errors.

           

          This is really common around tall buildings and downtown canyons or any constrained area with flat surfaces.  Less so due to tree cover...

          I've done my best to live the right way; I get up every morning and go to work each day...

            This is really common around tall buildings and downtown canyons or any constrained area with flat surfaces.  Less so due to tree cover...

             

            Yes, definitely much worse in urban canyon type environments.  But also exceedingly common in heavy tree cover.  You won't necessarily see the 2+ minute pace jumps in the tree cover, but if you are running a tempo run and trying to hit, say, 6:00's, when that watch jumps up to 6:45's it's just close enough and far enough to/from the truth that it makes you wonder if you are really slacking off even though you feel like you are working your tail off.  If you are using current pace, you will unfortunately see this a LOT in tree cover if you are paying attention, especially on products 610 and older.

             

            Yes, of course it is a "symptom" of the positional uncertainty, but this is not so obvious as it might seem.  The truth is that doppler based speed is available from the GPS chipset and it could be used.

            - Joe

            all running goals are under review by the executive committee.


            delicate flower

              Thanks for the responses.  One place in particular where this happens on every run is on the flat bike path in the middle of the suburbs.  Lots of tree cover, with a gully on one side of the bike path and houses on the other.  There are powerlines overhead as well...not sure if that makes a difference.  I can't understand why Garmin doesn't like this stretch.

               

              The last time I ran through there was from mile 3.5 to 4.5 of my run (out and back route and I turned around right at mile 4).  Garmin said my pace was around 11:45 from about mile 4.0 to 4.25.  Weird.  I picked up the effort this mile because I didn't want to see that ugly pace in my mile splits.  Big grin  My pace for the entire run was 9:06.

               

              ETA:  I use "current lap pace."  I've found "current pace" to be way too inconsistent.

              roboknee.

                ETA:  I use "current lap pace."  I've found "current pace" to be way too inconsistent.

                 

                Ok.  Smile   We just call it "lap pace".  To me "current lap pace" left me wondering whether you meant "current pace" or "lap pace".

                 

                It makes (more) sense now why you see the wonkiness -- it occurs from mile 4.0 - 4.25 -- in other words this is at the *beginning* of a new lap, so you are basically getting the *current* (noisy) pace for a while until it settles down into the average lap pace for the 5th mile.  I'll bet if you run that same stretch when it occurs late in a lap, say mile 4.75 - 5.0, if you can tack on an extra 3/4 mile somewhere, you will not see this problem at all because you basically have squished any variation by averaging over the preceding 3/4 mile.

                - Joe

                all running goals are under review by the executive committee.

                  p.s., 9:06.  Not bad for a guy with a bum knee!  Wink

                  - Joe

                  all running goals are under review by the executive committee.


                  delicate flower

                     

                    Ok.  Smile   We just call it "lap pace".  To me "current lap pace" left me wondering whether you meant "current pace" or "lap pace".

                     

                    It makes (more) sense now why you see the wonkiness -- it occurs from mile 4.0 - 4.25 -- in other words this is at the *beginning* of a new lap, so you are basically getting the *current* (noisy) pace for a while until it settles down into the average lap pace for the 5th mile.  I'll bet if you run that same stretch when it occurs late in a lap, say mile 4.75 - 5.0, if you can tack on an extra 3/4 mile somewhere, you will not see this problem at all because you basically have squished any variation by averaging over the preceding 3/4 mile.

                     

                    I run this section fairly often and the pace always gets knocked out of whack during this stretch no matter where in the mile it occurs.  The variation is definitely not as bad when it occurs later in the mile.

                     

                    FYI Joe, my doc gave me clearance to run as much as I want and just listen to my knee.  I set a new 10K PR in Boston two weeks ago, much to my surprise.  The knee couldn't be doing better.

                    roboknee.

                      I'm amazed at how well the GPS's work in the watches and phones actually considering how tiny they are.  I have a few spots with heavy tree cover where the splits get messed up, one area is right at the mile marker generally and typically the first mile logs as slow and the second mile logs as fast.  The trouble is when you start twisting and turning in heavy tree cover, then it really gets messed up and generally starts taking shortcuts over the tops of peoples houses.

                       

                      I've used handheld GPS's for many years for hunting and hiking and they have traditionally struggled with GPS signal in heavy tree cover.  I've recently upgraded to the Garmin 62S and it does much better in heavy tree cover, but I don't think I would want to carry it with me while I was running on a routine basis.

                       

                      Garmin GPSMAP 62S

                      I have thought about hauling it with me on some of my long runs when I wear my hydration backpack and comparing it with my GPS on my phone.

                       

                      Next time I'm in San Antonio and run along the riverwalk I'm going to not even bother using my GPS on my phone it struggled so bad last year when I was there, I'm just going to run based on time and log it that way.

                      Age: 45 Weight: 208 Height: 6'2" (Goal weight 195)

                      Current PR's:  Mara 3:48:09; HM 1:43:26; 10K 44:51; 5K 21:27


                      Miles to go

                        There's a spot where I usually run my tempos that doesn't have a great signal.  I like the spot for tempos because it's a nice flat two-mile paved path, so no traffic lights and good footing.  But I do know when I first head into the tree cover between two sets of soccer fields that my pace will be off.  No fun if I'm just starting a new interval, since I'm still a terrible judge of pace.

                        PRs: 5K: 25:35 / 10K: 53:03 / 10mi: 1:26:15 / HM: 1:55:02

                        Upcoming: HM 4/13


                        Will run for scenery.

                          Baboon, keep in mind that GPS is at heart a military technology intended to track fighter planes, rockets, missiles, etc.  You may have to slow down a bit if you expect it to keep up with you ! Joking

                          Stupid feet!

                          Stupid elbow!

                          NHLA


                            GPS does not work in the mts.  I lose signal three or four times every 5k.  XM radio does not work either.

                              FYI Joe, my doc gave me clearance to run as much as I want and just listen to my knee.  I set a new 10K PR in Boston two weeks ago, much to my surprise.  The knee couldn't be doing better.

                               

                              That is awesome!!!  Better yet to come because there must be something magical about ACL surgery.  In the two years after my ACL repair I PR'd just about every conceivable distance between 800 meters and marathon.  The layoff and rehab must have made me hungry!

                               

                              Go get 'em!

                              - Joe

                              all running goals are under review by the executive committee.

                              Gator eye


                                I did a out and back run in a heavily wooded trail last weekend, according to my Garmin I ran 7 miles out and 5 back. Roll eyes

                                12