[Talk-GB] Talk-GB Digest, Vol 50, Issue 2
Fozy 81
fozy81 at hotmail.com
Wed Nov 3 17:57:20 GMT 2010
Glasgow micro-mapping party Sat 6 November
When: Saturday November 6th 2010 11:00-16:00
Where: CCA: Centre for Contemporary Arts - Electron Club room
Contact
User:Hawkeye - Tim
http://wiki.openstreetmap.org/wiki/Mapping_Party/Glasgow
> From: talk-gb-request at openstreetmap.org
> Subject: Talk-GB Digest, Vol 50, Issue 2
> To: talk-gb at openstreetmap.org
> Date: Tue, 2 Nov 2010 07:38:56 +0000
>
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> Today's Topics:
>
> 1. Visualising speed limits (David Earl)
> 2. Re: Visualising speed limits (Andy Street)
> 3. Re: Visualising speed limits (Emilie Laffray)
> 4. Re: Visualising speed limits (Craig Wallace)
> 5. Re: Visualising speed limits (Ian Spencer)
> 6. Re: Visualising speed limits (Colin Smale)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 1 Nov 2010 19:40:38 +0000
> From: David Earl <david at frankieandshadow.com>
> To: Colin Smale <colin.smale at xs4all.nl>
> Cc: "talk-gb at openstreetmap.org" <talk-gb at openstreetmap.org>
> Subject: [Talk-GB] Visualising speed limits
> Message-ID:
> <AANLkTimvj0DOw2Nz=42mXQXDajjWmpPZVHqJGZtp3FKx at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Defaults would have to be set nationally or regionally.
>
> My TagCentral proposal would address this.
> http://wiki.openstreetmap.org/wiki/SotM_2010_session:_Tag_Central:_a_Schema_for_OSM
> I really must get round to doing something about it.
>
> David
>
> On Monday, November 1, 2010, Colin Smale <colin.smale at xs4all.nl> wrote:
> > On 01/11/2010 19:36, David Earl wrote:
> >
> > On Monday, November 1, 2010, Andy Allan<gravitystorm at gmail.com> ?wrote:
> >
> > On Fri, Oct 29, 2010 at 9:52 PM, Colin Smale<colin.smale at xs4all.nl> ?wrote:
> >
> > On 29/10/2010 22:22, thomas van der veen wrote:
> > You might like to take note that nothing is implicit in OSM. There are no
> > "defaults" as renderers or other consumers of the map data are unconstrained
> > as to how they handle missing tags. Ideally all roads should have maxspeed
> > explicitly tagged, even if it could be implied from the road class or other
> > information.
> >
> > I disagree quite strongly on this. I see little point in pointlessly
> > adding tags when they there is a sensible default. For example, we
> > don't need to tag 98% of roads as "oneway=no", and in the same way we
> > don't need to tag 98% of UK residential roads as "maxspeed=30mph".
> >
> > Life's too short for that kind of tedium. That's why we (actually do)
> > have implicit information in OSM.
> >
> > +1
> >
> > David
> >
> >
> > I agree with you both too. I was merely stating (for the benefit of a new mapper) that there is no working system of defaults. It would be very helpful if such a thing were to exist, but right now, there are no defaults. "oneway=no" is a bit of a no-brainer but the majority of "unwritten rules" ("implicit information") are not quite as obvious. In some cases, the wiki states that certain tags may be implied from others (e.g. highway=motorway implies oneway=yes) but these are, in general, poorly documented and information is fragmented and not easy to find. A welcome exception is the wiki page covering access tags for different highways[1]. Renderers or other "users" are just as much free to do their own thing as mappers are. The only thing that stops the whole shooting match descending into chaos is a set of agreements between producers and consumers. If it's not written down, and communicated appropriately, it might as well not exist. If you want to be unambiguous, use an explicit tag.
> >
> > So why not start documenting all these defaults or implied values? Here's a few suggestions to get the ball rolling.
> >
> > highway=motorway ? ?implies oneway=yes, lanes=2
> > highway=*, oneway=no ? ?implies ? ?lanes=2
> > highway=* AND lanes>=2 AND oneway=yes ?implies maxspeed=70mph
> > highway=* AND lanes>=2 ?AND oneway=no ?implies maxspeed=60mph
> > highway=* ? ?implies maxspeed=60mph
> > highway=residential ? ?implies maxspeed=30mph
> > junction=roundabout ? ?implies oneway=yes
> >
> > Colin
> >
> > [1] http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access-Restrictions
> >
>
>
>
> ------------------------------
>
> Message: 2
> Date: Mon, 01 Nov 2010 20:30:59 +0000
> From: Andy Street <mail at andystreet.me.uk>
> To: Gregory Williams <gregory.williams at purplegeodesoftware.co.uk>
> Cc: talk-gb at openstreetmap.org
> Subject: Re: [Talk-GB] Visualising speed limits
> Message-ID: <1288643459.15491.74.camel at americano>
> Content-Type: text/plain; charset="UTF-8"
>
> On Mon, 2010-11-01 at 16:44 +0000, Gregory Williams wrote:
> > Looks great. I think an OpenLayers Permalink anchor would make it even
> > better.
>
> Done.
>
> Cheers,
>
> Andy
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Mon, 1 Nov 2010 23:11:45 +0000
> From: Emilie Laffray <emilie.laffray at gmail.com>
> To: Andy Allan <gravitystorm at gmail.com>
> Cc: talk-gb at openstreetmap.org
> Subject: Re: [Talk-GB] Visualising speed limits
> Message-ID:
> <AANLkTimR8vUh1+486z_qtKtGy5nX0axxsZUGw9Utzq6g at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> On 1 November 2010 17:57, Andy Allan <gravitystorm at gmail.com> wrote:
>
> > On Fri, Oct 29, 2010 at 9:52 PM, Colin Smale <colin.smale at xs4all.nl>
> > wrote:
> > > On 29/10/2010 22:22, thomas van der veen wrote:
> >
> > > You might like to take note that nothing is implicit in OSM. There are no
> > > "defaults" as renderers or other consumers of the map data are
> > unconstrained
> > > as to how they handle missing tags. Ideally all roads should have
> > maxspeed
> > > explicitly tagged, even if it could be implied from the road class or
> > other
> > > information.
> >
> > I disagree quite strongly on this. I see little point in pointlessly
> > adding tags when they there is a sensible default. For example, we
> > don't need to tag 98% of roads as "oneway=no", and in the same way we
> > don't need to tag 98% of UK residential roads as "maxspeed=30mph".
> >
> > Life's too short for that kind of tedium. That's why we (actually do)
> > have implicit information in OSM.
> >
> >
> +1
>
> Emily Laffray
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> ------------------------------
>
> Message: 4
> Date: Mon, 01 Nov 2010 23:33:07 +0000
> From: Craig Wallace <craigw84 at fastmail.fm>
> To: talk-gb at openstreetmap.org
> Subject: Re: [Talk-GB] Visualising speed limits
> Message-ID: <4CCF4E33.30908 at fastmail.fm>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 01/11/2010 19:32, Colin Smale wrote:
>
> > So why not start documenting all these defaults or implied values?
> > Here's a few suggestions to get the ball rolling.
>
> Implicit speed limits are documented on this page:
> http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Maxspeed
>
> Some other defaults (eg for oneway) are listed on this page:
> http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing
>
> Though maybe it would be useful to have a page with a UK specific
> summary of all this? Something like "UK roads tagging"?
> Similar to the tagging guidelines for other countries:
> http://wiki.openstreetmap.org/wiki/Category:Tagging_guidelines_by_country
>
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 02 Nov 2010 01:50:52 +0000
> From: Ian Spencer <ianmspencer at gmail.com>
> To: talk-gb at openstreetmap.org
> Subject: Re: [Talk-GB] Visualising speed limits
> Message-ID: <4CCF6E7C.6030700 at gmail.com>
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>
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> ------------------------------
>
> Message: 6
> Date: Tue, 02 Nov 2010 08:38:53 +0100
> From: Colin Smale <colin.smale at xs4all.nl>
> To: talk-gb at openstreetmap.org
> Subject: Re: [Talk-GB] Visualising speed limits
> Message-ID: <4CCFC00D.2040803 at xs4all.nl>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> Ian,
>
> You're right, my detailed knowledge of these things is definitely below
> par! I spend too much time outside the UK to follow all this. My
> "suggestions" were more-or-less intended to catalyze a discussion so I
> am not surprised they are not correct.
>
> I think your post proves the point I was trying to make. Defaults and
> the rules surrounding their use can be complex. If the rules are simple
> enough and can be documented, we might get away with it, but then some
> of the subtleties might get optimised out of the rules leading to
> incorrect inferences if mappers don't put the subtleties back in with
> explicit tags. So once again I will make a plea for documenting the
> defaults very clearly, and/or explicit tagging. And to be clear, I am
> *not* talking about adding oneway=no to almost every way.
>
> An interesting contrast between the UK and Holland (maybe other
> countries as well), correct me if I'm wrong:
> * In the UK, you commit an offence (e.g. parking where it is forbidden)
> based on a local authority by-law, although the absence of decent
> signing could be a valid mitigation.
> * In Holland, the offence is to disobey a sign; if it's not signed
> (properly), you haven't committed an offence.
>
> A significant difference, which leads to more consistent, more explicit,
> less confusing signage in NL, without having to e.g. measure the
> distance between street lights. The "built-up area" starts where the
> sign says it does.
>
> Colin
>
> On 02/11/2010 02:50, Ian Spencer wrote:
> >
> >
> > Colin Smale wrote on 01/11/2010 19:32:
> >> So why not start documenting all these defaults or implied values?
> >> Here's a few suggestions to get the ball rolling.
> >>
> >> highway=motorway implies oneway=yes, lanes=2
> >> highway=*, oneway=no implies lanes=2
> >> highway=* AND lanes>=2 AND oneway=yes implies maxspeed=70mph
> >> highway=* AND lanes>=2 AND oneway=no implies maxspeed=60mph
> >> highway=* implies maxspeed=60mph
> >> highway=residential implies maxspeed=30mph
> >> junction=roundabout implies oneway=yes
> >>
> >> Colin
> >>
> >
> > Someone has not been on their speed awareness course, have they?
> > (ahem!) 70mph is based on dual carriageway. A dual carriageway does
> > not need two lanes to qualify, and this is more common these days as
> > you find that on certain dual carriageways a lane has been blanked out
> > for some distance.
> >
> > Also, to nitpick, your implications are not all correct, oneway=true
> > and lanes >=2 does not imply any sort of maximum speed, as any decent
> > one-way system in a town would match this, and you cannot rely on a
> > trunk road to identify this as truck roads often run through built up
> > areas. In other words, there are sensible defaults, but you cannot
> > imply speed limits as easily as you suggest from the tags you present
> > there. Similarly, although again a sensible default, residential roads
> > with 40mph or more are not uncommon.
> >
> > However, that is pedantic, and I'd agree in principle with defaults
> > being sensible, indeed road signage in the UK is based on the
> > principle that you can infer the speed limit from the presence or
> > absence of street lighting if there are no contradictory speed limit
> > signs (motorways being an explicit exception to the rule). This has
> > saved me from a speed camera incident or two in the past.
> >
> > So to go down a proper mapping exercise to determine actual speed
> > limits, we should be mapping the limits of street lighting as that is
> > the relevant attribute, though to be fair, I can barely recall an
> > example where a council has relied on the presence of street lighting
> > alone to control traffic speed.
> >
> > Changes in legislation a few years ago make understanding this
> > implicit speed limit more relevant, as it is now no longer a
> > requirement to signpost increases in speed limits in certain
> > scenarios, not is it a requirement to have signs either side of the
> > road in all cases and your only clue might well be that you see a
> > repeater sign somewhere up the road - the theory being that when you
> > exit a minor road, you carry on at the same limit until you are
> > informed otherwise (e.g. exiting on an unlit country lane which was 30
> > mph onto another unlit country lane you might find a repeater sign a
> > bit down the road saying 40mph without an intervening speed limit sign
> > to show the increased speed. So a little bit of care is needed in
> > mapping speed limits to ensure you map based on the subtleties.
> >
> > Of course, these speeds do not apply to vans which are not car based,
> > nor buses and lorries. A surprising number of white van men drive at a
> > licence losing 30mph over their 60mph speed limit on dual carriageways
> > and 50mph on single carriageways; and perhaps you should not curse the
> > lorry on a typical single carriage A road where they are limited to
> > 40mph by law, 50mph on a dual carriageway. It gets more interesting
> > for lorries on a motorway, because although they are allowed to do
> > 60mph in terms of speed limit, lorries now have to have a speed
> > restrictor and digital tachograph that limits them to 56mph to comply
> > with EU legislation so this is the de facto limit.
> >
> > So any maxspeed needs to account for the type of vehicle, (or it
> > should be a code). This is even more the case in Europe where it is
> > common to see sections of autobahn or trunk road where the speed limit
> > is explicitly varied by type of vehicle.
> >
> > FWIW, Tom Tom maps speed changes pretty accurately, though it is not
> > completely reliable, but the competition is pretty high.
> >
> > Spenny
> > (currently pointless in mpre ways than one!)
> >
> >
> > _______________________________________________
> > Talk-GB mailing list
> > Talk-GB at openstreetmap.org
> > http://lists.openstreetmap.org/listinfo/talk-gb
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