On the wiki for piers it states: “Small piers tagged as open ways way are often rendered too large, giving an incorrect impression of the distance between piers.”
and
“For a narrow pier draw a linear way way and add man_made=pier.
For a wider pier create a closed area area and add man_made=pier and area=yes.”
So it’s a little unclear as to which I should do for smaller piers, I’ve been mapping them as areas for now, but I don’t want to be inconsistent with what the rest of the community is doing. Advice would be helpful. Thanks!
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Do not take what you can find on the Wiki as absolute truth, it is written by people without a formal process.
The text is not illogical to me but if you have detailed information I see no problem also mapping a more narrow pier as area, it is just a way of more detailed mapping.
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Don’t be afraid to draw small piers as areas. Some have irregular shapes that cannot be mapped with a single way, such as those shaped like a T or a P; generally, to represent these types of piers, mappers add a second way, which gives the false impression that there is a second or third pier for a single element.
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I don’t think it really matters what way you map them. That said, like the difference between a simple footway and a pedestrian plaza, area=yes can be used to create something much wider, like Way: Brighton Pier (3451897) | OpenStreetMap - something like this, I would only maps as an area.
Mapped as way: OpenStreetMap - something like this, I would only maps as a way.
Mapped as way: OpenStreetMap
Mapped as area: OpenStreetMap - with these two, even though some of the piers are close together, there is no difficulty discerning one from the other.
Important: many things that are called “piers” are not piers, but breakwaters, quays or similar objects. The important part is that the water can flow under a pier. One definition is that a pier is “a bridge into the sea”. Notably, sometimes piers float on the surface of the water, they aren’t supported by the sea bed. 
This is a pier: OpenStreetMap
This is a breakwater: OpenStreetMap
These are quays: OpenStreetMap
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Both are pretty common:
Overpass search for piers mapped as closed ways.
Overpass search for piers mapped as lines.
And formal processes on wiki are often resulting in output of even worse quality
I rewrote page a bit deleting some misleading claims and moving some to extra section to indicate their lesser importance if any.
Is it now less confusing?
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I just took a look and it’s much more clear. Appreciate your help!
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And thanks for reporting your confusion on forum! Please do it again if you encounter something similar.
Wiki can be useful but it is sadly having a lot of dubious content like this.
(it was not so bad, because it was clearly confusing - and sometimes you have understandable and clear but altogether wrong descriptions)
It’s totally fine to map a T or P shaped pier as two separate ways if that’s required. Any data consumer that assumes that there must only be one OSM way element for a pier and uses that as the basis of some calculations is flawed.
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