[OSM-talk] Questions about levels and fractional levels as well as how to handle them.

[Colin Smale]

Hallo John, 

A level is not a unit of measurement like a metre or a kilogram. If
level 1.5 exists, it only tells you that it is between level 1 and level
2. If a landing on a staircase between level 1 and level 2 is to be
assigned a level, it wouldn't make any difference if you called it 1.1
or 1.9, unless there are other fractional levels around of course. It is
the sequence of the levels that is important. If level numbers are
treated as floating point numbers, 1.10 would be before 1.9 (i.e. closer
to 1.0). If you treat them as strings, 1.10 is different to both 1.1 and
1.100 and may give unexpected results when sorting objects into level
order, e.g. for rendering. 

You may of course wish to use a convention of 0.1 levels = 0.5m for
example, if your levels are about 5m above each other. Having said that,
an integer level number is usually associated with a floor, and usually
increases in an upward direction. So something at "eye level" standing
on level 1, would definitely be between 1 and 2.

--colin 

On 2017-12-21 17:21, John Karr wrote:

> Hello All,  
> 
> I hope this is the correct mailing list to ask this question. I'm new to the OSM community and had a question which I hear is very controversial. I'm part of a team working on an app for indoor navigation using simple indoor tagging. The audience for this app are individuals who are blind/low-vision so that they can navigate indoor spaces.  I'm wondering how best to handle fractional levels when parsing the repeat_on tag. Currently, the project does not account for fractional levels and everyone involved seems to have a different opinion on the matter, but not very many solutions emerged from the discussion. And with that question more seem to arise. For instance, how common are fractional levels mapped in the indoor plans? Are there any standards or best practices associated with determining which fraction to dub a level (i.e. 1.5, 1.2, 1.02, etc.)? I would love to know how the community feels about this topic and how best to proceed. Also if anyone has an example of a repeat_on
tag that contains fractional levels and how those are expressed that would be very much appreciated. 
> 
> Thanks, 
> John Karr
> Technology Product Research - Programmer I
> American Printing House for the Blind
> 1839 Frankfort Avenue
> Louisville, KY 40206-3148
> jkarr at aph.org 
> 
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