[Tagging] what does maxheight=none mean?

moltonel 3x Combo moltonel at gmail.com
Thu Oct 30 11:26:29 UTC 2014


On 30/10/2014, Pieren <pieren3 at gmail.com> wrote:
> On Wed, Oct 29, 2014 at 6:24 PM, moltonel 3x Combo <moltonel at gmail.com>
> wrote:
>
>> And both tags are
>> definitive, whereas "maxheight:signed=no" (or whatever) is just
>> waiting for a better tooled or experienced mapper to do the survey.
>
> No. The survey is done : "there is no legal height restriction under
> this bridge". Of course, anyone is free to come back and add more tags
> like the physical height or the material and 3d shape of the bridge,
> etc. But the most interesting information for apps checking clearance
> (e.g. for routing) is there => no legal restriction here.

Counter-no :p If there's a maxheight:signed tag but no maxheight tag,
the survey isn't done. I agree with the definition of the plain
"maxheight" key from the wiki :

> In most cases this expresses a legal limit, though there are places where this is used differently. Note that if it is desirable to establish a difference between a legal and a physical maxheight, this should be the lesser of the two.

So "maxheight" technically isn't the legal limit, it's the smaller
limit between maxheight:physical and maxheight:legal. In general if
there's a legal limit it'll be the smaller one, but one could imagine
a 4m limit on the road and a no legally-specified limit on a 3m
bridge.

If there's no legal limit, you should still add the "maxheight" tag.
It's the tag that routers actually care about, it's important.
Differenciating between maxheight:physical and maxheight:legal is a
nuance that most people do not care about. Estimate the physical limit
and leave a fixme if you've got no better source. If you want to tag
the fact that there is no legal limit or no sign, use a different key
than "maxheight" (maxheight:legal and maxheight:signed comme to mind).



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