Re: [OSM-talk] Bridges / viaducts for railways
On Feb 2, 2008 11:12 PM, Gervase Markham [EMAIL PROTECTED] wrote: Martijn van Oosterhout wrote: Around here the water levels can vary +/-0.5m (just before the bridge there's a gauge so you can tell at any particular moment if you'll fit). Should the height here be the minimum maximum_height? The maximum height when the water is the heighest? Yeah, it seems to me that putting max_heights on something where one of the surfaces moves is fraught with possible problems... TBH this seems more of a hobbyist requirement anyway. If you're making a map for serious use you'd do it more like a network (like roads) and have routes between junctions that say what the maximum class of boat that can pass through this route. There is a standard classification for such things. No route planner for boats is seriously going to rely on checking the height of every bridge on the way. In the end we have to rely on the official classification for waterways anyway, because if a waterway is not officially classified as permitting a certain class of boat, then a council can just build a non-opening low bridge over it and you're SOL. Then again, this may be academic in the UK, I understand they don't have any waterways that could be classified in the smallest category. Have a nice day, -- Martijn van Oosterhout [EMAIL PROTECTED] http://svana.org/kleptog/ ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
On Tuesday 29 January 2008 08:13:57 Michael Collinson wrote: As to way forward, I suggest there are 3 options: - Depreciate the viaduct tag entirely [*] - Use viaduct=yes - Complement the generic bridge=yes tag and develop a specialist bridge type tag for bridge devotees with precise architectural/engineering definition. FYI I've created a proposal that covers the first two and invites someone to develop the third: http://wiki.openstreetmap.org/index.php/Proposed_features/Viaduct Kind regards, Tom ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
Steven te Brinke schrieb: As a sailor I like to know if a bridge is a moveable one, and I think this is also interesting for cars, because they might need to wait. So I agree that bridge=true is not enough, I would like to be able to have a bridge=moveable. You probably don't want to know whether a bridge is movable but whether it is high enough for your boat: max_height=5m To provide details for movable bridges, relations could be used: member=way xyz type=propset# marks a group of properties propset_type=temporary # temporary change max_height=0# unlimited time_on=09:00 # the proerties can only be made available time_off=18:00 # during these opening hours The having-to-wait property can simply be tagged as traffic_lights. Claus ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
Martijn van Oosterhout wrote: Around here the water levels can vary +/-0.5m (just before the bridge there's a gauge so you can tell at any particular moment if you'll fit). Should the height here be the minimum maximum_height? The maximum height when the water is the heighest? Yeah, it seems to me that putting max_heights on something where one of the surfaces moves is fraught with possible problems... Gerv ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
On Jan 30, 2008 12:52 AM, [EMAIL PROTECTED] wrote: Hi, On Mon, Jan 28, 2008 at 07:16:25PM -, Andy Robinson (blackadder) wrote: Why is it not a property like bridge, cutting etc. and will it render correctly? Should it be changed to viaduct=yes? Ewww, yuck... boolean flags. Personally I would tag as: railway=rail bridge=viaduct bridge and viaduct are two separate types of structure so strictly speaking bridge=viaduct is incorrect. They might be different to you as a civil engineer... to me a viaduct looks like lots of bridges next to each other (i.e. huh, what's the difference, really?) ;-) Actually, it's more of a thing I have about using on/off, yes/no, true/false type tags - they generally are not right in my opinion. For instance, take the same principle applied to roads highway=yes motorway=yes We use highway=motorway here - if nothing else it stops you doing the silly highway=yes motorway=yes secondary=yes Similarly, something can't be both a bridge and a viaduct. Therefore you want something like over=bridge or over=viaduct a) you reduce the keyspace, and b) you can't have bridge=yes viaduct=yes As usual in my case over is a bad name for a key. I guess that's why I stuck to the more generic bridge before, with bridge=yes being the general case. It's the same as saying bridge=suspension, rather than bridge=yes, suspension=yes (or even bridge_type=suspension - eugh). Maybe something like transit= would be better (in the sense of how this way gets from A to B) and could then include tunnel, cutting, embankment, etc in the list of values as well as bridge and viaduct. Basically, I would say that every object-type key (i.e. not things like name=) should have as many non-coexistant values* as possible (if that makes sense), and that single flags (i.e. where a key only ever has one value) should be discouraged wherever possible. * i.e. you can't have both on the same object, such as suspension and viaduct That's usually the plan I think. The main problem we have with putting this into practice, is that to maintain an optimal number of tags we need to know the entire tagging domain before we start... which we don't. So taking your example, if instead of bridge=yes we allow bridge=suspension, we don't actually have a problem (assuming everybody agrees to assume the existence of the bridge tag implies a bridge regardless of the value, maybe excluding no). But if we had started with transit=bridge/tunnel/ferry, then we'd still need the bridge tag anyway because it's probably not sensible to add the transit=suspension_bridge etc, simply for the ease of processing. Ofcourse you could argue we need the transit tag, and just don't have it. I think for many of these things where we have x=yes/no, we find that there is often a number of subtypes that could be substituted for the yes. Although most people probably wouldn't know how to classify them, and just want to record the main type. Dave ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
[EMAIL PROTECTED] wrote: Maybe something like transit= would be better (in the sense of how this way gets from A to B) and could then include tunnel, cutting, embankment, etc in the list of values as well as bridge and viaduct. structure=bridge structure=tunnel ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
Hello, As a sailor I like to know if a bridge is a moveable one, and I think this is also interesting for cars, because they might need to wait. So I agree that bridge=true is not enough, I would like to be able to have a bridge=moveable. It is also possible to add the type of bridge (lift, swing, bascule, ... - wikipedia has some beautiful animations of them: http://en.wikipedia.org/wiki/Moveable_bridge). So I think a viaduct=yes or a viaduct=type would be a good idea. At least the current way viaduct is used doesn't seem to be a good one. And I think a viaduct and a bridge are quite different things, so it's no problem to give them their own tag. Steven Dave Stubbs schreef: That's usually the plan I think. The main problem we have with putting this into practice, is that to maintain an optimal number of tags we need to know the entire tagging domain before we start... which we don't. So taking your example, if instead of bridge=yes we allow bridge=suspension, we don't actually have a problem (assuming everybody agrees to assume the existence of the bridge tag implies a bridge regardless of the value, maybe excluding no). But if we had started with transit=bridge/tunnel/ferry, then we'd still need the bridge tag anyway because it's probably not sensible to add the transit=suspension_bridge etc, simply for the ease of processing. Ofcourse you could argue we need the transit tag, and just don't have it. I think for many of these things where we have x=yes/no, we find that there is often a number of subtypes that could be substituted for the yes. Although most people probably wouldn't know how to classify them, and just want to record the main type. Dave ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
At 06:57 PM 1/28/2008, Tom Chance wrote: Hello, I'm a bit confused about these tags: railway=viaduct bridge=yes cutting=yes embankment=yes I assume that 'viaduct' covers these sort of elevated rail lines so that bridges are just for, well, bridges over other ways: http://www.mybrightonandhove.org.uk/images/uploaded/scaled/railway_viaduct_aerial.jpg http://www.betterpublicbuildings.gov.uk/assets/images/finalists_2006/jamestown/jamestown_large.jpg http://www.24hourmuseum.org.uk/content/images/2005_1745.JPG Why is it not a property like bridge, cutting etc. and will it render correctly? Should it be changed to viaduct=yes? This is one of those old tags. Both bridges and viaducts were originally nodes. I also think it reflects the earlier more UK-centric tagging - viaducts are to the non-specialist those 19th century long tall multi-arched stone bridges that grace many an English valley and town. I ignore it entirely. Certainly if used, viaduct=yes would make more sense. As to way forward, I suggest there are 3 options: - Depreciate the viaduct tag entirely [*] - Use viaduct=yes - Complement the generic bridge=yes tag and develop a specialist bridge type tag for bridge devotees with precise architectural/engineering definition. Mike Stockholm * And before I set off storms of UK protest again, I mean remove it from map features NOT preventing anyone using or rendering it! :-) ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
Hello, On Tue, 29 Jan 2008 10:11:34 +, Dave Stubbs [EMAIL PROTECTED] wrote: On Jan 29, 2008 8:13 AM, Michael Collinson [EMAIL PROTECTED] wrote: As to way forward, I suggest there are 3 options: - Depreciate the viaduct tag entirely [*] - Use viaduct=yes - Complement the generic bridge=yes tag and develop a specialist bridge type tag for bridge devotees with precise architectural/engineering definition. I think this is a very sensible way of moving forward, based on the replies so far. At the moment I use the bridge tag for viaducts, which looks ugly and is inaccurate. I'd suggest that viaduct=yes looks similar or identical to bridges on Mapnik, perhaps with a slightly lighter casing if it looks like a big dark blobby nightmare where there are a lot of them. From what I think I understand, the railway lines out of Waterloo station in London are pretty much going to be classed as going over a viaduct all the way to Clapham Junction? These are raised manmade structures about the height of a house, mostly with arches etc. Same for lines coming out of London Bridge and most other London stations. In fact the district line (railway=subway) between Parsons Green and East Putney is also viaduct? That's my understanding too, London and other cities will be *full* of viaducts! Hence my concern, given that it's pretty handy to know how ways go over/under each other especially when you're walking around half-lost. Kind regards, Tom ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
[EMAIL PROTECTED] wrote: Sent: 28 January 2008 7:01 PM To: Tom Chance Cc: Talk Openstreetmap Subject: Re: [OSM-talk] Bridges / viaducts for railways On Mon, Jan 28, 2008 at 05:57:24PM +, Tom Chance wrote: I'm a bit confused about these tags: railway=viaduct bridge=yes cutting=yes embankment=yes Why is it not a property like bridge, cutting etc. and will it render correctly? Should it be changed to viaduct=yes? Ewww, yuck... boolean flags. Personally I would tag as: railway=rail bridge=viaduct bridge and viaduct are two separate types of structure so strictly speaking bridge=viaduct is incorrect. for cutting I would have thought more like (this is a suggestion, there is probably a better way): railway_level=-1 or railway_level=cutting and for embankment railway_level=1 or railway_level=embankment We already use layer=+/-5 for setting display layering and I always envisaged the same simple system could be used for cuttings and embankments. Map features has the really odd (IMO): railway=viaduct (node) highway=viaduct (node) I think these are legacy from when I first put up map features when we didn't have ways and all that and I wanted some method of showing a viaduct icon. Could be wrong. No harm in leaving this as the tag for a node though. with the comment of something like A high or long bridge long and node don't go together as far as I am concerned ;-). You also don't know what type of railway goes over the viaduct, as you lose the railway= information. A possible, but slightly odd, example would be an underground train going above ground and over a viaduct - it would be railway=subway, bridge=viaduct. If memory is correct, I think the DLR does that in some places in London (railway=light_rail, bridge=viaduct)? I'd prefer to see railway=rail for all rail corridors and a secondary tag for the type of service/stock used - ie metrorail/subway/underground/freight etc etc etc But it's no big deal to understand what's implied without extra tagging. Cheers Andy Not sure what others do, though... Cheers, -- Matthew ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] Bridges / viaducts for railways
Tom Chance wrote: Sent: 28 January 2008 5:57 PM To: Talk Openstreetmap Subject: [OSM-talk] Bridges / viaducts for railways Hello, I'm a bit confused about these tags: railway=viaduct bridge=yes cutting=yes embankment=yes railway=viaduct doesn't sound right. Sticking my civil engineering hat on for a minute, viaduct=true|yes|1 would be correct for a multispan bridge carrying anything other than water (which would be aqueduct=true|yes|1) A bridge is a single span structure carrying anything other than water. Water doesn't have a single span equivalent, just use aqueduct= still. A cutting or an embankment is what the transport corridor has been built on when the natural ground rather than a structure is being considered. Almost all transport corridors have traditionally been built using the Mass Haul Curve principal which attempts to balance the amount you cut out with the amount to fill to make embankments. This process keeps the road or rail alignment as close to a constant or manageable grade as possible while minimizing the distances you have to transport spoil. For sections of a route not sitting on a structure there are actually three conditions: cutting embankment at_grade The latter is where no excavation has been made (other than the removal of topsoil and any other unsuitable surface deposits). Cheers Andy I assume that 'viaduct' covers these sort of elevated rail lines so that bridges are just for, well, bridges over other ways: http://www.mybrightonandhove.org.uk/images/uploaded/scaled/railway_viaduct_ aerial.jpg http://www.betterpublicbuildings.gov.uk/assets/images/finalists_2006/jamest own/jamestown_large.jpg http://www.24hourmuseum.org.uk/content/images/2005_1745.JPG Why is it not a property like bridge, cutting etc. and will it render correctly? Should it be changed to viaduct=yes? The train lines around south London are pretty much always one of the above and I'd like to get the tagging right. Kind regards, Tom ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
