GPS Accuracy

Yes i know. But how about Garmin foot pod sdm4 for distance and pace???

If the courses is useless, does it make sense to buy footpod  for a distance and real pace?

The courses are not useless. To me they are invaluable and one of the key things that keep me training, pushing and feeling well. If I want to know how I actually perform on a given distance though, I participate in a timed race or run laps on a track.

Regarding the foot pod, I have been using the Garmin one for years as it gives me faster and more exact feedback for pace than any GPS does. So when I do intervals/repeats it is very valuable to me. I highly recommend it. From my understanding, the Stryd is even better but way more expensive.

You can read more about foot pods and the Stryd here: http://fellrnr.com/wiki/Footpod

Just to clarify : Garmin is measuring the distance not only from the GPS, but adding its own calculation (from the accelerometer possibly, or something else, nobody knows), to try to fix the GPS errors. Unfortunately, it leads to too short distances in most cases. So the distance shows by Garmin is NOT the GPS distance. If you want to see this distance, you can't really fix it on the workout in Garmin Connect. if you sync with Strava, you can ask Strava to recalculate (one click) and it shows the GPS distance. One is too short (Garmin), one is usually a bit too long (GPS). WIth the Fenix 6, I think it's better than the 5X with its Mediatek chipset, so I prefer to fix the distance on Strava, it gives something pretty accurate. 

Of course, it means that DURING the workout, you don't have a very very accurate distance. For the pace I think it's even worse, Garmin is doing yet another black magic thing ;) 

So if you need the right pace and distance DURING the workout, the footpod is the best solution. If you don't mind that much, the Strava fix is not bad, at least it's free ;) 

Ok I understand. But how useful would the course be, as each time it would show me distances calculated incorrectly by Garmin, not correct ones from the map.

Well, it's not a 20% error, we are talking about acceptable errors for most cases. It really depends how important it is for you to have the most precise distance. Or live pace on the watch. I have ran for a year with a 5X, the distance is maybe not as precise as other watches, but in my case, it's not a problem. Maybe i'm missing 1% of the distance. I still ran it, and I'm not doing interval training, nor running races where the pace is critical. And in any case, NO GPS watch will give you a very very accurate distance, there are always little errors. If you REALLY need the right distance and pace, footpod (if possible a Stryd or as good) is quite mandatory. GPS is not reliable enough for precise distance / pace, Garmin or not Garmin involved. 

The same in the woods. With the open sky it is very accurate but error is significant if you have some trees cover. 

I wonder how my Garmin Vivosport  for $ 100 there is a better stable pace and distance between buildings and trees than the  Fenix 6.

If you haven’t already, I would try out the three different GPS settings

• GPS
• GPS + GLONASS
• GPS + GALILEO

and see if any of them gives you better tracks. Otherwise it seems like the Vivosport really is the better device for navigating your area :)