Changes

* '''How fast am I running?''' Knowing how fast you're running can be a nice to know, or it can be vital for your training or race performance. Because of the nature of GPS, watches that rely on GPS signal alone tend to have serious problems with current pace. Without the ability to display current [[Pace From A Footpod]] while getting all other data from GPS, the 620 can't answer this question. The mediocre GPS accuracy exacerbates this issue, and I've seen the pace estimate wildly wrong on the 620. The 620 would be my top pick for marathon runners, but I firmly believe that this is a killer feature, as accurate pacing is essential for a good marathon performance.* '''Where am I? '''The 620 has no navigation features. If you're lost, the 620 won't be much help. * '''What's my cadence? '''[[Cadence]]''' '''is one of the most critical and often overlooked aspects of running. If you get your Cadence right, many other things naturally fall into place. Not only does the 620 get [[Cadence]] from a [[Footpod]], it will also get it from the Garmin Run Heart Rate monitor. There is also support for Cadence from the internal accelerometer, though I find that's not as accurate. The Cadence alerts are especially useful for keeping you on track.

=GPS Accuracy Issues=The Garmin 620 had some well-known [[GPS Accuracy]] issues, but this has been resolved with a firmware update. * The 620 has remarkably good repeatability, which is a measure of how likely it is to give the same indicated distance on a particular part of the course. This can create an illusion of greater accuracy than is actually there, and it also suggests that the TomTom is smoothing out curves too much. * On the out-and-back turnaround the TomTom does a little worse than I'd expect for its overall rating, again suggesting too much smoothing. * Running in a straight line on the other hand, is a fairly easy task for most GPS watches, and the TomTom really excels, giving the most accurate reading of any device. * The TomTom does about how you'd expect going under the bridge. * I not had any issues with the TomTom acquiring or maintaining the GPS signal, unlike some other devices. {| class="wikitable" |- valign="top"|[[File:BridgeGarmin 620 (3.30).jpg|none|thumb|x300px| You can see the 620 does a reasonable job most of the time. There are a number of tracks where it gets a little lost, and there are some issues with the 620 reacquiring the signal after the bridge. It does poorly around the twisty section, cutting the corners too much due to smoothing. Interestingly, it does a better with the sharp turn seen on the right side of the diagram. The lap markers in blue are more widely dispersed than they would be with a better device. (This diagram has tracks color coded with green indicating good accuracy through to read indicating poor accuracy, and the lap markers as blue dots.)]]|[[File:BridgeGarmin 620 (pre-v3.30).jpg|none|thumb|x300px| The earlier version of the firmware does rather horribly. The tracks are widely spaced and the 620 often gets rather lost. (This diagram has tracks color coded with green indicating good accuracy through to read indicating poor accuracy, and the lap markers as blue dots.)]]|- valign="top"|[[File:AccuracyGarmin 620 (3.30).jpg|none|thumb|x300px| This close up section of a zigzag shows the 620 tracking okay, though here again we see the wide spacing of the tracks. There are more green lines than red, and the 620 is coping reasonably well. (This diagram has tracks color coded with green indicating good accuracy through to read indicating poor accuracy, and the lap markers as blue dots.)]]|[[File:AccuracyGarmin 620 (pre-v3.30).jpg|none|thumb|x300px| The earlier firmware shows how badly the 620 was doing. The lines are almost noise and the lap markers are widely scattered. (This diagram has tracks color coded with green indicating good accuracy through to read indicating poor accuracy, and the lap markers as blue dots.)]]|- valign="top"|[[File:ZigZagGarmin 620 (3.30).jpg|none|thumb|x300px| Here you can see the 620 displaying the typical GPS behavior with the tracks that have the green lines shifted slightly down and to the left, blue up and to the right. This is less marked that other devices, but you can see the pattern. You can also see the lap markers shifted. (This image has the tracks color-coded for direction, with green coming from the right, blue from the left.)]]|[[File:ZigZagGarmin 620 (pre-v3.30).jpg|none|thumb|x300px| With the earlier version of the firmware the behavior is pretty much lost in the noise. It does seem like the green tracks are closer to the trail, but it's hard to be sure. (This image has the tracks color-coded for direction, with green coming from the right, blue from the left.)]]|}=Resolving GPS Accuracy =If you are having GPS accuracy issues, then the following suggestions may help.

* '''Altimeter. '''GPS is far less accurate vertically than horizontally, so a barometric altimeter can provide a much better idea of your ascent and descent. It can also be useful for navigation if you're ascending or descending a mountain. In some races I've been far more interested in how much ascent is left rather than the distance to the top.* '''Navigation.''' The navigation capabilities are useful if there is a risk of getting lost. I've made good use of this feature when running in an unfamiliar city, or when running remote trails.* '''Downloadable Apps'''. Smart watches have got is used to the idea of a device that can be extended with new functionality, and this concept is being introduced to running watches.* '''Extended battery life'''. Some porches can extend the battery life by turning the GPS reception off for short periods. This can dramatically reduce GPS accuracy, but it's a useful trade-off for some ultramarathons.* '''Graphs'''. Instead of simply displaying a numeric value for things like heart rate, some watches will display a graph of the value over time, giving you a sense of how things are progressing.* '''Web Configuration'''. Some watches allow you to setup the configuration via a web site, and then download your changes. This is vastly easier than fiddling with the watch.