GPS not accurate, position is a few hundred yards off

ryjoel What GPS settings and recording mode are you using? 

Not sure what you mean about GPS settings...recording mode is Smart

GPS settings:  GPS or GPS + Glonass or GPS +Galileo

Pls share a public gconnect or strava activity link or upload the original FIT file of the activity in zipped format here. 

Imho the single-band Sony gps chip in these newer cycling/running Garmin units are very weak, the multipath error filtering is low. I hope the 840 will have the dual-band Sony gps chipset what the GPSMAP 66SR has, that would be a new era for cycling tracking devices (of course, a good antenna design is also necessary for pinpoint tracks)

To be more accurate....when I am riding, my position is not correct, the route does not overlay the map  of roads correctly.  its a few  hundred yards off.  The screen shows a route that is offset against the map.  

What maps are you using?  Is the time correct on the unit?

Base map and yes the time is right.

The low detail base map or the Garmin cyclemap?

Low detail base map

You need to be using the Garmin cycle maps or third party equivalents to correctly see if your position is correct. The base map is low detail and is not accurate at higher zoom levels. It is only there for something to orientate yourself at low zoom levels when the high detail cycle mapss or equivalents would be too dense to display.

The base map also doesn't have routing so can't be used for turn by turn navigation.