Two Antennas (was RE: "Blunkett u-turn on data privacy plans")

[David Hansen]

On 5 Mar 2003 at 12:03, Roland Perry wrote:

> Indeed, and if we are talking about surveying in the USA, depending on
> what you define as "level" [1] I think you can be plus or minus six
> feet by the time you get from one coast to the other.

It's one of the reasons the Panama Canal has locks. Even if it could 
have been built "level" there would still need to be a lock, because 
the (mean) water levels are somewhat different on either side of the 
continent. Evening the levels out via a tiny canal would produce 
interesting currents, even before one starts to consider tidal 
effects.

 > [1] Do you walk across the USA with a spirit level, to get a 
> "gravitational" level, or do you do something based on a spherical
> geometry and some agreed place for the centre of the earth.

I don't think that the earth is very round either.






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