At one time it was thought Rose Peak was the highpoint of Alameda County at 3,817ft, but in 1991 Dinesh Desai was studying maps and found a point to the east with an extra contour, making for an elevation of 3,840ft+, which he named "Discovery Peak" and has since become official with the BGN as of 2011. It turns out there is a second point, 1.6 miles SE of Discovery Peak, that has a spot elevation of 3,841ft. Trees intervene to make it exceedingly difficult to get a level between the two points, and since the spot elevation is a mere 1-foot over the closed contour, it is easy to dismiss it as "unlikely". I had actually visited this second point four years ago but didn't have a GPS or other measuring intrument and didn't give it any further thought.
I was back in the area today to visit another nearby peak and went over both points a second time, now equipped with a Garmin 550t. Though the absolute elevation reading isn't too accurate, I've found the relative measurement between two close points to be fairly good in other situations, within about 5ft of previously reported elevations. Today's reading showed Discovery Peak to be 18ft lower than the spot elevation point, which caught me by surprise.
Does anyone know of technical reasons why this measurement technique is not to be trusted?
(I know there are many who could care less about county highpointing, and I apologize for wasting your time here. Thank you for not using this post to point out how silly this all is - we highpointers are well aware of this, but can't help ourselves.)
View of Peak 3,841ft from Discovery Peak:
Summit block of Peak 3,841ft (about 8ft in height):