I have seen where a surveyed corner was 50' off from the GPS coordinates.
Fence lines out west more often than not are 30-60 yards off of where OnX and/or GPS says they should be, let alone 50 feet. I am guessing GPS would show the "correct" location vs what was determined by a Gunter's chain 150 years ago, but I am sure that could be contested in court if a citation was issued.
Variations could also be from your GPS being set to WGS84 and the mapping data being based on NAD83, or vice versa....Lots of possibilities when it comes to that kind of thing.
