On Wed, Feb 21, 2018 at 9:05 AM, François Lacombe <fl.infosrese...@gmail.com> wrote: > In the same time, systems like "Los Angeles Aqueduct" are called aqueduct > and are composed of canals, tunnels and pipelines. > https://en.wikipedia.org/wiki/Los_Angeles_Aqueduct > > That's why I like the definition of Aqueduct like a system and not like a > precise building. > > Am I wrong ?
I think you're right. The Aqua Marcia, Aqua Ano Vetus, Aqua Anio Novus, and Aqua Claudia were all known as 'aqueducts' and were systems that were tens of km, in canals where possible, but mostly in underground conduits. There were pressurized syphons for valley crossings. Only the terminal portions of the aqueducts, as they approached the City, or crossings of deep valleys, were on arcades - but these make the tourist pictures, so people get the incorrect impression that 'aqueduct' is synonymous with 'arcade'. The arcades were used as the water approached Rome because the whole system was gravity fed, and having the water up on a high arcade was the way to get decent water pressure at the tap. New York City's system runs on a similar plan, but with pressurized tunnels. The system is entirely gravity driven from its sources in the Catskill Mountains to the tap. The upper sources of the system are as far away as https://www.openstreetmap.org/way/135512500 (for the Catskill Aqueduct) and https://www.openstreetmap.org/way/134694145 (the tunnel doesn't appear to be mapped) for the Delaware Aqueduct. Using 'canal' for https://www.openstreetmap.org/way/135512500 - when it's a pressurized syphon - is suboptimal, but is the 'least wrong' thing in current tagging. _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
