Originally Posted by
njkayaker
It's not noise because the device isn't measuring your elevation. It's using a database (DEM), which, as I said, has issues and not ideal for elevation gain.
The issue might have been more apparent if the complete data (horizontal location and elevation) was provided.
Oh, that's likely. A post-event method, like strava has as an option, uses known elevation points. But it has to estimate the exact elevation at spots in between, and that's difficult on roads along a hill slope. Where exactly is the road surface?
And on ridwithgps, for planning routes, sometimes a fairly recent road cut isn't known, so it shows a steep climb. Or a creek crossing bridge drops down to the creek level and back up again.
The most obvious is the tunnels on the Blue Ridge Parkway. The local elevations go up and over the ridge line, making very steep grades on the route there.