[OSM-talk] [tagging] Feature Proposal - RFC - Clearance

[Aun Johnsen (via Webmail)]

On Thu, 30 Jul 2009 08:43:22 +0000 (GMT), John Smith
<delta_foxtrot at yahoo.com> wrote:
> --- On Thu, 30/7/09, Aun Johnsen (via Webmail) <skippern at gimnechiske.org>
> wrote:
> 
>> much more. Since many countries have two different signs
>> for max legal
>> height and max physical height, and its usages can be very
>> different, why
>> not allow this in tags?
> 
> So why not just use maxheight=* and maxheight:legal=* ?
> 
>> By saying that there is no difference between maxheight and
>> clearance is
>> for me the same as saying there is no difference between
>> highway and
>> cycleway, tourism and historic. 
> 
> I fail to see the difference, most maxheight matches the clearance to
> within 15cm, maxheight is a restriction tag and clearence would be a
> restriction tag stating the same with a second name.
> 
> There is however a big difference with highway and cycleway, both
physical
> and legally, there is usually very little difference between legal and
> physical clearance.
> 
> You also mentioned sailboats under bridges, are you planning to update
the
> clearance 24 hours a day, 7 days a week as the tide goes in and out?
You are clearly not familiar with the term "free sailing height" which
refers to the height from mean sealevel (used in marine charts), up to a
portion of the bridge span which os over the safe channel. This value is
stated in all marine charts as a reference to any ships captain for him to
verify that his vessel can pass safely under the bridge with his current
air draft. There is no need to correct this more often than the bridge is
reconstructed as you will correct this value towards tidal information
available for the closest port.
-- 
Brgds
Aun Johnsen
via Webmail