Revision as of 16:39, 29 September 2015

The Garmin 620 is wonderful running watch. It's much smaller than many comparable watches, but it packs in more features while retaining great usability. It's my top pick for most runners, though if you're on a tight budget, there are other contender's such as the Garmin 310XT or the Suunto Ambit2 that offer better value for money. For a simple evaluation of a GPS watch, I look at how well it can answer some basic questions:

• How far did I run? This is the most basic question, and the 620 has somewhat reasonable, but not great GPS accuracy, so its estimate of how far you've run needs to be treated with a little caution.
• 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.

The 620 is not a good choice for ultrarunners, as its battery life is too short. See Watches for Ultrarunning for more details.

The Garmin 620, showing the display of Cadence, Vertical Oscillation and Ground Contact Time. Note that the display is color, but I found the colors muted and not always easy to distinguish.

1 Garmin 620 Pros

• With the updated firmware, the GPS accuracy is reasonable. It's not as good as the Polar V800 or some of the other watches, but it's okay for most usage.
• The 620 is small and light, but the display is quite legible for its size. I find it much easier to read than either the Garmin 610, Suunto Ambit2 or the Garmin 10. (It's a lot better than the Garmin Fenix 2.
• Like the Fenix 2, the 620 will show and record Cadence, Vertical Oscillation (VO) and Ground Contact Time (GCT). The 620 has a nice display of Cadence, VO, and GCT that gives a color coded indication of how well you're doing.
• The 620 will provide alerts when a metric is out of range. The alert for Cadence is really useful and one of my favorite features of the 620. Before the firmware fix for GPS accuracy I'd wear the 620 just for the Cadence alert and use another watch for tracking distance.
• Like several other devices, the 620 displays Training Effect, an indicator of how hard or effective a training session is.
• The 620 includes an estimation of the Recovery Time before the next workout, just like the Fenix 2.
• The 620 will cache the locations of the GPS satellites for the next few days, which will reduce the satellite acquisition time when travelling to a new location. In my usage the satellite acquisition was very rapid.
• The touchscreen works better than any other I've tried while running.
• There is a prediction of your V̇O₂max, which worked well for me, but I would not rely on its accuracy.
• The 620 will upload your workouts to Garmin Connect via WiFi without needing a computer. It will also link to a smart phone to upload a workout as it takes place, which is nice for folks tracking you during a race, though it means wearing the watch and the phone together.
• The 620 will cache the locations of the GPS satellites for the next few days, makes for faster satellite lock. However, if you've not connected the 620 to the internet for a few days, the 620 can be painfully slow to acquire a lock.
• The 620 will not display Heart Rate Variability but it is possible for it to record Heart Rate Variability for later analysis. To enable this recording, you need to download a special FIT file from the firstbeat.com web site.

2 Garmin 620 Cons

• There is no way of displaying your current pace from the Footpod while using GPS for overall distance and course. While the 620 now has good GPS accuracy, it is not sufficient to give useful current pace information. For situations where pacing is critical, such as running a marathon, a Footpod works better. (Earlier versions of the firmware would always display the pace and distance from the Footpod when it's connected, but this was fixed in a recent update.)
• The 620 includes an internal accelerometer to give you an idea of pace and distance while running on a treadmill without a footpod. While firmware updates have improved the accuracy, I found it was too far out to be of any use, giving a display that was off by 1-3 minutes/mile. A lot will depend on your running style and how you use a treadmill.
• There is no map display or navigation, but on a device this small it would be hard to make that useful anyway.
• The battery life is short for ultramarathons, but it is fine for the most runners.
• You need to have the new HRM for the new features. It will display Heart Rate and calculate Training Effect with the older Garmin HRM, but not Ground Contact Time or Vertical Oscillation.

3 GPS Accuracy

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.

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.)	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.)
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.)	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.)
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.)	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.)

4 Resolving GPS Accuracy

If you are having GPS accuracy issues, then the following suggestions may help.

1. Make sure your firmware is up to date. The 620 actually has two firmware installations, one for the watch functionality, and one for the GPS. The GPS firmware needs to be at 3.30 or above.
2. Synchronize the 620 with the Garmin software to update the EPO data which is used to improve GPS startup time.
3. Leave the 620 in "ready to go" mode with a good view of the sky for at least 20 minutes. There is information (the almanac) that can take 12.5 minutes under ideal conditions to download from the satellites. In theory the 620 should get all of the satellite data from the EPO file, but the almanac might help.
4. If none of these steps work, do a factory reset.

5 What's Missing

While I don't consider these missing features as 'cons', it's worth understanding the features that are missing compared with other watches.

• 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.

Please support this site This review was made possible by readers like you buying products via my links. I buy all the products I review through normal retail channels, which allows me to create unbiased reviews free from the influence of reciprocity, or the need to keep vendors happy. It also ensures I don't get "reviewer specials" that are better than the retail versions.

6 Visual Comparison

Garmin 620 top	Garmin 620 side
Suunto Ambit2 top	Suunto Ambit2 side
Suunto Ambit3 top	Suunto Ambit3 side
Polar V800 top	Polar V800 side
TomTom Cardio Runner top	TomTom Cardio Runner side
Garmin Epix top	Garmin Epix side
Garmin 920XT top	Garmin 920XT side
Leikr 1 top	Leikr 1 side

7 Comparison Table

I evaluate running watches in three distinct ways. Firstly, you can use a watch on its own, without any kind of Footpod. This is probably the most common way runners use their watch, but you miss out on a lot. The second rating is with a standard Footpod that is available quite cheaply. These Footpod's can be reasonably accurate once the calibrated, but calibration is a little tedious. The final evaluation is with the Stryd Footpod, which is vastly more accurate than any other type of Footpod, or and more accurate than GPS. The table below looks at the score, and the value for money of each watch for each of the three conditions. (I’ve also tested the Apple Watch 3, but I’ve not included it in these tables as it’s not really a running watch.)

The score is the sum of how well each watch can answer the four basic questions (how far, how fast, where are you, what's your cadence), plus some bonus points.

1. The "How far you've run" will be based on GPS only for "without Footpod" and "with Standard Footpod", but based on Stryd if supported in the "with Stryd Footpod" table..
2. How fast you're running assumes you're using a Footpod if it's supported, otherwise the rating is 0-2 based on GPS accuracy.
3. The "Where are you?" is based on various navigation features such as back to start, breadcrumbs, and preloaded maps. For some watches, you have to turn GPS off to get the benefit of Stryd, so those watches have worse "where are you scores" with Stryd than without.
4. The cadence score uses 1 point for an internal cadence sensor, 2 points for footpod support, 1 point for support from chest strap cadence, and 1 point for cadence alerts.
5. I give 1-2 bonus points for application support, 1-2 bonus points for data upload, 1-2 bonus points for Optical Heart Rate Monitoring, and 0-1 bonus points for battery life.
6. Value for money is the score divided by the price (at the time I last updated the table.) Your needs may be different, so you might weight the different aspects of the watches differently, or be basing your decision on different criteria totally. Hopefully this table will give you a good starting point for your decision.

7.1 Score Breakdown without a Footpod

7.2 Score Breakdown with a Standard Footpod

7.3 Score Breakdown with a Stryd Footpod

7.4 Basic Features

8 Navigation Features

For "navigation":

• Color Maps gives you full color maps, rather like a smart phone, with roads and paths marked out.
• Track Outline is a display of where you've run, rather like a breadcrumb trail. If there are maps, the outline is superimposed otherwise this is just the outline on its own without any context.
• Course Outline is an outline of a route that can be downloaded. I've found this useful during ultras or in unfamiliar cities where I've needed to know where to go.
• Back To Start is a simple arrow point to your starting point, so it won't help you backtrack.
• Back To Waypoint returns you to a previously marked location using a simple arrow to point.
• Compass. A magnetic compass can help you orient yourself or the map. Without a magnetic compass you have to be moving for the GPS to give you a sense of direction.

(Older Reviews: Polar RC3 GPS, Soleus 1.0, Motorola Motoactv.)