pethier@comcast.net wrote:
>> One small point, could that datum be
>> plus 694.10 feet?
>>
>
> It's all in how you look at it. We say "minus" because the USGS number on a
>plan is larger than the City Datum number.
>
> USGS sea level reading - 694.10 = Saint Paul City Datum
>
>
Right... I see now. Any UK surveyor working in the US is going to need a
speedy re-education course, and vice versa. This side of the pond datums
(data??) are positive numbers above sea level (at Newlyn in Cornwall
coincidentally).
snip
> Sometimes a surveyor will not call for benchmarks and just pick a random
>place on the site and call it "100.00". I hate that. When you design a
>house, you should know the elevation of available sewer. It is expensive and
>annoying to make sludge flow uphill. The builder ought to spec the job for
>the surveyor to supply elevations tied to a standard.
>
>
As a contractor I find that method of levelling (temporary bench mark)
easier to work with. Less numbers to enter in the level book. Granted,
eventually the numbers have to be adjusted related to an Ordnance
Benchmark for final record. Still, the coming of total stations for
survey work makes these considerations irrelevant.
Nick Brearley
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