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The local direct measurement IS altitude above sea level. The problem is that they weren't using the same reference points.
by rjp0008 12y ago
The local direct measurement IS altitude above sea level. The problem is that they weren't using the same reference points.
- what_ever 12y agoAnd the description says that they did consider the difference between two reference points - 27cm. They just considered the difference in the opposite way. So instead of 27cm - 27cm = 0 difference they ended up with 27cm - (-27cm) = 54cm difference in the levels.
- DougWebb 12y agoNot using the same reference points is the odd part. If they were building a tunnel, it would make sense, but for a bridge they could see from one side to the other. They should have been able to set a reference point on one side and translated it across to the other side. That's a direct measurement, and it doesn't matter at all where that reference point is relative to sea level or anything else.