# [Tagging] The actual use of the level tag

Greg Troxel gdt at lexort.com
Mon Jan 21 01:49:17 UTC 2019

```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.

```