[Tagging] The actual use of the level tag

[Greg Troxel]

Here's a perhaps-radical set of comments and suggestion:

  in any building, there is a set of names (which often but not always
  look like numbers) for levels.  These are evident in the elevators
  (buttons inside, matching values outside) and in things painted on
  walls, on room numbers. etc

  In the US, you'll typically find something like B/G/2/3, corresponding
  to level -1, 0, 1, 2.   Presumably in the UK that's B/G/1/2.

  (probably not relevant) In the US, there is a star in the elevator
  next to the floor which is considered ground.  This is purely about
  how to get out of the building.  Basically, when you get in an
  elevator, if you wish to get outside, push the button with the star,
  and then follow exit signs.  Almost always, this is "G".

  In the US, you'll often find 12 and then 14, just because people who
  number floors think other people don't want to be on a floor numbered
  13.

  M (for mezzanine) is often in between G and 2, and often but not
  always has some notion of being less than a proper full floor

  some buildings have two different floors that are both at-grade in
  different parts of the building.

  therefore, floor numbering is not something that can be mapped to a
  number.  Instead, it is a set of names, which often look like
  sequential numbers.

  So,

     there should be a tag with a list of names in order, something like
     "B2 B G 2 3" (for a building with a sub-basement below the
     basement), and

     floor values should take on one of those names, and

     there should be a tag that denotes the floor that is most
     considered the ground floor, in the above case "G".

     probably do not try to think about buildings that have different
     ground floors in different places

This totally blows up the notion of numeric levels, but given the above
ordered list of floor names, one can compute an n-floors-above
relationship from any two floor names in the list.


Another example is a building I've been in with floor names

  P6 P5 P4 P3 P2 P1 G 1 2 3 4 5 6 7 8 9

yes, that is six levels of below-grade parking.  It might actually have
a B between P1 and G - I don't remember.  It had two sets of elevators,
one set P6-G, and one set G-9.