All units in osm should be the metric value, unless the units have
been name spaced. Whenever I enter mph units, I use the tag
maxspeed:mph=30 etc as this is the most accurate way of representing
the data. I'm not going to spend time converting between mph and kph,
when entering the data, that is for whoever uses the data to do. In my
opinion, it is far better to use the local units, but always have it
clear as to the units, when they are not metric/most common.
Shaun
On 5 Oct 2008, at 13:45, Ed Loach wrote:
I've not done much maxspeed tagging to date, for various reasons,
but the main one is that Map Features says that maxspeed should be
in km/h. Or more accurately looking at the history for the template
for that section [1], the original conversion stated:
"{{{maxspeed:desc|Maximum speed, country-specific units}}"
And the revision 3 minutes later changed it to
"{{{maxspeed:desc|Maximum speed in km/h}}}"
With a description for the edit (from Pieren) of
"(restore metrics text, although it should be discussed)". I don’t
know where to find the versions pre 2008 to find out what it said on
older versions.
I noticed that “should be discussed” note, but don’t know where to
look for that discussion. However, the decision to put in km/h has
made a mess of the maxspeed tagging on UK roads, especially as there
is both a conversion table in the wiki quoting whole numbers, and a
multiplication factor to use. See for example Tagwatch [2] where the
most common maxspeed is 48, followed by 30mph (the format I’ve been
using), and lower down come 48.28, 48.28032, 48.27808 and 48.3. I’d
also guess that the ways tagged as maxspeed=30 mean 30mph. If we had
stayed with assumed country-specific units then the tagging would
have been more consistent, easier for the user to tag, and not
require a conversion to a random number of decimal places.
The maplint mention in the message subject is because Map Features
defines the value for the maxspeed key as being a number, so any way
I’ve tagged as =30mph, 20mph, 10mph, national or 40mph (as I did for
the first time yesterday) gets highlighted in the maplint
information, rendering it (no pun intended) next to useless for
checking other mistakes I may have made in the tagging.
I have no suggestion what to do about either of these situations
though. I wouldn’t have been bothered at all if maplint hadn’t
suddenly started highlighting lots of ways in the area… I realise
that that is down to the word number in the wiki page causing the
validation to fail with the mph in the value.
Thinking about it I have a similar issue with maxheight. Most of the
signs these days I think quote in metres, but I tagged one the other
day as so many feet and inches (possibly 13’9” – I forget), as I tag
what is on the sign and not what a metric conversion is (to the
centimetre, metre, decimetre, millimetre?). It seems I’m not the
only one [3].
I suspect what I’d like most would be for maplint to recognise that
if the value contains valid units for whatever the key is (optional
units), then it wouldn’t highlight the way as in need of checking. I
believe maplint is common to both Mapnik and Osmarender (as it’s
highlighting ways on Mapnik which don’t yet show as I only added
them yesterday), and I know how to rebuild the not-in-map_features
information as I did it recently to add some keys that *were* in Map
Features but not being recognised by the [EMAIL PROTECTED] client when it
generated the maplint tiles, but it would probably need the perl
code that creates the XML tweaking to cope with optional units in
some way (a bit like it currently doesn’t like * in the value
column, IIRC, or “User Defined”).
It’s raining here incidentally, which is why I thought I’d rant on
email instead of going out mapping a bit more of the area.
Ed
[1]
http://wiki.openstreetmap.org/index.php?title=Template%3AMap_Features%3Arestrictions&diff=73032&oldid=73031
[2] http://tagwatch.stoecker.eu/Great_britain/En/
keystats_maxspeed.html
[3] http://tagwatch.stoecker.eu/Great_britain/En/keystats_maxheight.html
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