While driving and passing those elevation signs in the mountains, my Garmin is easily within ~50 ft. It would probably be more accurate if I slowed down. Hiking it seems to be quite accurate relative to topo maps. But that's a 12 channel GPS receiver. How many channels does it take for a GPS to meet SARSAT/COSPAS spec? It probably has that much accuracy in elevation too. ?500 yards?
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Better is the Enemy of Good Enough.
Okay, what’s your point??