A brief navigation-focused review of the Garmin Edge 820
My bike club has been going paperless for some years now, increasingly shifting from printed cuesheets to having GPS route maps from ridewithgps be the authoritative version of a ride. I've been a paper holdout but this clearly wasn't tenable for ever, and so recently I decided to deal with the issue by getting a GPS unit. After a bunch of reading on the Internet, I ended up buying a Garmin Edge 820. The short version of this review is that I wound up returning it as somewhere between 'unreliable' and 'unfit for (this) purpose'.
As both a rider in club rides and a ride leader, the most important thing for me is that my GPS unit provide easily usable and completely reliable turn by turn directions for following RWGPS routes exactly. If it isn't completely reliable all of the time, I can't trust it and I need a paper cuesheet as a backup and a cross-check. Although the Edge 820 has many nice features and can do this some of the time and on some routes, it doesn't do this all of the time and I wound up deciding that its failures were sufficiently common that I couldn't live with them and would be perpetually frustrated with my 820 if I kept it.
The 820 has two sources of turn by turn directions: onboard Turn Guidance, which the unit calculates itself (quite slowly) from your route and its own maps, and .tcx Course Points from suitably exported RWGPS routes. Turn Guidance is easily usable, with clearly readable turn alerts that pop up well in advance of the turn, but not reliable; sometimes it will stop (especially if you have to go off route for 'too long'), sometimes it will try to send you off the route, and sometimes it will give you bizarre directions like 'Turn Left into Trail' instead of 'Turn Left to street <X>' (sometimes it will combine these). TCX Course Points are completely reliable (as far as I saw) but not easily usable; the Edge 820 shows them in a much smaller font that's hard for me to read and doesn't pop them up in advance of the actual course point.
(RWGPS has an inadequate hack semi-workaround for the 'no advance alert' issue.)
There are plenty of good things about the 820; I really liked having the during-ride data it could present to me, it did so in a way that's customizable and flexible and far more readable than my basic wired bike computer, it's nice to have the ride track and related data to look at later, and so on. And it had good battery life; I did roughly eight hours of riding (with breaks) and wound up at 65% battery left. There were also other frustrations and flaws and things I didn't entirely like (the map display used colours in a way that wasn't all that easily readable in bright sunlight, for example). But the killer issue was that I couldn't trust the turn by turn navigation, and that wound up trumping everything else.
(When Turn Guidance worked it was great; I could completely tune out from remembering the next turn and keeping an eye out for it and tracking where on the route we were, and just be riding away heads-up and seeing the scenery and so on. And it works great on certain sorts of rides.)
The Edge 820 also has a meta-problem, which is that Garmin is famously unresponsive to customer issues and that many or perhaps all of these navigation issues are not new in the 820; they are in fact long standing in many Garmin Edge products. Some Edge products have been worse (apparently some used to crash if your route crossed over itself, for example). All of this left me feeling that none of my issues were likely to be fixed in future firmware revisions, and in fact from stuff I read on the Garmin forums it sounded like some of the issues are intrinsic to Garmin's approach to calculating Turn Guidance directions.
(The story as I read it is that Garmins basically slice your route up into 300m or so segments and then do their own routing from the start to the end of each segment. If you are unlucky, there is an alternate path from the start to the end that the Garmin likes better than the actual route, and so the Edge will try to send you off down it. This matches the pattern that I saw in 'tries to send me off course' Turn Guidance failures. This is a somewhat weird approach, but it makes a peculiar kind of sense if you start with software that doesn't accept routes from outside and then hack in that feature later.)
Interested parties can peruse my thread on the Garmin Edge 820 forums about this.
(This review was sparked by @YoloPerdiem's request.)
Sidebar: The sorts of rides Turn Guidance is likely to work great on
Based on my experiences and readings, I think that Turn Guidance is mostly likely to work flawlessly on routes that basically don't double back on themselves or otherwise touch and where the turns are widely separated from any other roads or trails (and where you don't go off route because of surprise construction or whatever). The former situation seems to often confuse the Garmin, and the latter means that the Garmin can't misroute you because it has no other choice but the route's own turn. This happens to describe many of our rides out in the countryside, where the Garmin Edge 820 worked pretty well for me.
Unfortunately it doesn't describe city riding at all, and many of the club rides I go on and lead are city ones. Almost all of the really terrible turn by turn failures that I experienced were in city riding.