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#1 2009-01-20 13:12:25

Ben
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From: United Arab Emirates
Registered: 2006-05-23
Posts: 213

Rendering a map of the trunk road system in the UK

I've brought this up many times before in other places, but I'm gunna do so again, becuase It rather frustrating having to use the data within the restrictions of the tags, rather than for anything you wish.  It's trunk roads.

It still seems impossible to render a map of the UK trunk road system.  I don't mean a map of all roads with blue or green signs, but the trunk road system as shown, here, here, here and here...etc...,etc....

Grouping roads by signage is all ok, but we also need to tag them so we can filter off half the roads and produce an uncluttered map.  Having way too many features appearing in a small space makes a map almost unusable in most cases.  Try using this for quickly finding where you are and where you have to go for example.  It's considerably worse than an OSM example, but OSM's low zooms are still unesseserly cluttered, and there not particularly practical.   I have a feeling Google had an influence on this, rather than much discussion.

I still see it as strange, that we tag primary roads as trunk based on signage, as a google search for 'UK trunk roads' will show the Motorways and HA managed highways, but I guess it's just one of many of OSM's oddities.  It's also contradictory to Wikipedia which says "Trunk roads in England are managed by the Highways Agency".  What really matters though is 'not being able to make a map'.  We can be odd but lets not be restrictive.  Can we please either have an additional tag for the real trunk road network, or just tag maintenance=highways agency where applicable.  (This is assuming that these map examples are only showing HA managed roads??)

There was a wiki page somewhere, which I am failing to find, which lists some basic principles of map rendering.  There are a few points I recall that are being forgotten about here and on other matters, but I think a rule I go by, that applies here, is that when ever something is mapped so commonly that it clutters, tag more specifically.

Also the 'tagging based on signage' arguement somewhat falls apart for various lower status highway keys, but that can be saved for another day!


Ben

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#2 2009-01-23 09:15:30

Richard
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From: Charlbury, UK
Registered: 2007-04-24
Posts: 408
Website

Re: Rendering a map of the trunk road system in the UK

Heh, haven't had this one for a while.

Feel free to put something like maintenance=highways_agency - people tag the stuff they're interested in, as you know; so just as many people will map a housing estate without noticing whether the roads are part of the NCN, so will many map an A- road without thinking of who's responsible for the maintenance. It doesn't stop you putting it in yourself.

That said, I think maintenance, specifically, is the wrong tag. DBFO roads like the A50 (M1-M6) and A417/A419 (M4-M5) are actually maintained by a private company like Connect Roads.

Maybe the network tag (already used in relations) would be better? Given that the DfT generally refers to the Strategic Road Network, also encompassing most - but not all - motorways, you could use network=england_strategic. Or, maybe, authority=highways_agency.

On the clutter argument, as a cartographer, I don't think OSM's UK maps are too cluttered. Rather, it's the rest of the world (outside Germany, the Netherlands and the States) that is too sparse. That's fine, we've not finished mapping yet. wink

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#3 2009-01-23 10:23:55

EdLoach
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From: Clacton-on-Sea, UK
Registered: 2009-01-20
Posts: 59
Website

Re: Rendering a map of the trunk road system in the UK

Ben wrote:

I still see it as strange, that we tag primary roads as trunk based on signage, as a google search for 'UK trunk roads' will show the Motorways and HA managed highways, but I guess it's just one of many of OSM's oddities.

Strangely though many of the other online mapping services also seem to colour their A roads based on the road sign colouring, so OSM isn't unique in this respect.

But, from http://wiki.openstreetmap.org/wiki/Wiki … om_A_Roads

In the UK, the OSM rule goes like this:

green signed A roads: highway=trunk
black-and-white signed A roads: highway=primary
(It might sound confusing if you're used to hearing A roads described differently. Sorry, it's just how we do things round here.)

I realise the OSM wiki also contains:
http://wiki.openstreetmap.org/wiki/Unit … runk_Roads
which contains

Please note that this is a formal, and little-used, UK government classification. It does not necessarily mean that these are the only roads which should be tagged with highway=trunk. Many UK OSM users follow the practice that all green-signed A routes (ie primary routes) are tagged highway=trunk, while black-and-white-signed A-roads (ie non-primary routes) are tagged highway=primary.

A Roads maintained by the Highways Agency (or are DBFO/privately financed projects managed by the HA) which are designated as Trunk

That page also misses trunk roads shown on the HA maps near here, so it isn't really much use for anything   (One example, A120 from A12 to the port at Parkeston, or somewhere close to that).

To date, every HA map I've seen of their routes contains a Crown Copyright notice which means it shouldn't be used for entering data in OSM (which I take to include road classification information). Which only leaves the colour of roadsigns to go by as far as I can tell.

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#4 2009-01-25 23:13:31

Ben
Member
From: United Arab Emirates
Registered: 2006-05-23
Posts: 213

Re: Rendering a map of the trunk road system in the UK

Richard: It's too cluttered if you have to slow down because you can't see a route through in it's entirety, without slowly tracking a line along, or you need to lean closure to the screen.  My opinion isn't independent from professional experience also, but points should be judged just for what they are, although I value a lot of what you say, but just becuase it seems to be right!  I do think currently OSM is for the most part above average in relation to being selective in what shows up when and just how good it looks generally, but there it is certainly cluttered to the extent that it could be made easier to read and look cleaner without having to exclude needed data, but just shift some data up a z_ level.   I do currently stick maintenance=highways_agency, but realistically OSM follows the main rendering rule sheets.  If issues aren't addressed and things resolved then rule sheets seldom change.

On DBFO roads:  As these are part of the real backbone of roads, rather than all green signed roads, it would be good to be able to group them in, if possible.  You clearly know more than me on highways, so really..just state what would work as a tag, and I'll use it, and maybe get round to proposing it.

EdLoach:  This grouping does exist on other online maps I agree, and I did mention google above in relation to this.  I don't think usually we should use 'other maps do it' as an argument for doing things on OSM, unless other maps doing it has really made something, such as a symbol, instantly recognisable, and therefore the most suitable for OSM.  On the other hand, it can be assumed the ‘other mapsÂ’ have done things for a reason, so it may be a starting block.

I have seen that wiki page many times before, and It wasnÂ’t the building block or origins of how things are in the UK tagging scheme.  Like most things in OSM, the current tags are just what was most commonly used, rather than there being much thought prier to usage.  Standardisation then gets built on this, renders built on that, and standardisation enforce by the renderers.  highway=tracks and highway=steps tags for example, for some reason avoiding the highway=bridge cull.  Both tags coming into existence before any really rendering of maps, and therefore the flaws with  them not being so apparent until later on.  The wiki now states that's the way, but the origins are messy.

On the second link, there is a link at the top which shows the source map, and has that data just been derived from that?...if so why is on the wiki at all?.  Is this as it's seen as fair use as the map is copyright rather than HA's data which could arguable be skimmed off and applied to our map, if it is free of that copyright restriction.  IÂ’ve asked all the questions in this paragraph before, but got next to no answers on it.

Most HA roads I've seen (this may be chance?) have a sign stating that they are HA managed on them, so if we are stuck for maps, hopefully this would help.

Last edited by Ben (2009-01-25 23:14:18)


Ben

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