[Talk-us] Shaped highway shields - trying to revive

[Martijn van Exel]

Agreed. I think it's really nice to have active thinking and work around this. The key is to get the rendering stack people involved. Perhaps Paul Norman can function as a liaison?

Martijn

Sent from my iPhone

> On Aug 24, 2018, at 12:06, Evin Fairchild <evindfair at gmail.com> wrote:
> 
> Really glad to see that someone is reviving this and actually taking the step to get it rendered. Frankly, I never understood why Phil didn't do this in the first place. I even mentioned this to him at the time (can't remember his response though).
> 
> -Evin (compdude)
> 
>> On Wed, Aug 22, 2018, 2:21 PM Kevin Kenny <kevin.b.kenny at gmail.com> wrote:
>> (I apologize in advance to the tile-serving community if this message
>> is inappropriate. I see that traffic on that list is largely limited
>> to highly specific technical discussions, but couldn't see a more
>> appropriate forum.)
>> 
>> For several years now, I've been using the support code for shaped
>> shields in OSM, originally developed by Phil! Gold and Richard Weait,
>> to render North American-style maps. A typical example can be found at
>> https://kbk.is-a-geek.net/catskills/test4.html?la=41.4143&lo=-74.4233&z=14
>> In that view, you can see distinct shields for Interstate, US, New
>> York, and county routes, and at least one concurrence (New York 17M
>> aligned with US 6). Incidentally, Phil's is the only renderer that
>> I've seen that can make sense of cases like West Virginia's bizarre
>> double route numbers, as seen in
>> https://kbk.is-a-geek.net/catskills/test4.html?la=41.4143&lo=-74.4233&z=14
>> .
>> 
>> The visual distinction among highway shields is really necessary in
>> North America, where there are so many different route networks
>> overlaid.
>> 
>> In the course of working with the code, I've made a number of changes
>> and become seriously out of sync with the main development line, which
>> appears to be moribund. (Phil! and Richard have not answered recent
>> queries; I suspect that I have obsolete contact information, but the
>> messages also have not been returned undelivered.)
>> 
>> Accordingly, I've (quite reluctantly) created my own repository -
>> https://github.com/kennykb/osm-shields - with material from the
>> project. The shield templates to be found there are mostly those of
>> Phil! (I added only a handful), but the code to manage shields is
>> almost entirely new. Some significant changes are:
>> 
>> The list of shields to be rendered is obtained from the database
>> itself, rather than being predetermined by a configuration file for
>> each network. This has the disadvantage that refs that are known to be
>> problematic may be rendered (but in most cases they ought to be
>> unsigned_ref). On the other hand, it has the distinct advantage that
>> as mappers continue to create the route relations, the corresponding
>> shields appear virtually automatically.
>> 
>> The composition of shield clusters, rather than being handled by a
>> stored procedure in the database, is done using a GroupSymbolizer in
>> Mapnik. I suspect, given the dearth of discussion that I find in a
>> Google query, that I'm the first user to attempt to use
>> GroupSymbolizer with actual open-ended shield clusters, and therefore
>> that I've trodden new ground in the path from database to renderer. I
>> encourage developers who are interested in the GroupSymbolizer to read
>> at least https://github.com/kennykb/osm-shields/wiki/Using-the-GroupSymbolizer
>> - it has a number of tricks to structure the results in a way that the
>> GroupSymbolizer can consume and that renders well. The disadvantage to
>> using the GroupSymbolizer is that Phil!'s shield clusters were rather
>> more attractive visually, since they were aligned to lie in the
>> direction of a way. The advantage is that the current approach can run
>> on an unpatched Mapnik, as opposed to Phil!'s original, which requires
>> at least patching Mapnik to use a read/write connection to the
>> database.
>> 
>> Managing, reliably, the association between ways and the routes in
>> which they participate requires a couple of database tables that a
>> stock osm2pgsql does not produce. I would very much appreciate any
>> commentary from developers of osm2pgsql and Mapnik, particularly,
>> about the issues discussed in
>> https://github.com/kennykb/osm-shields/wiki/Maintaining-the-association-between-ways-and-routes
>> What I'm currently doing works well for my own use, which is driven by
>> daily updates to extracts at Geofabrik, but will obviously not scale
>> to a whole planet and minutely updates.
>> 
>> Finally, I'd really like to invite anyone with the necessary SVG
>> skills to contribute shield graphics for the missing networks. If
>> you're also a programmer and want to take a whack at the rest of the
>> procedure in https://github.com/kennykb/osm-shields/wiki/Adding-new-networks,
>> and give me a pull request or ask for help, that would be even better,
>> but even the artwork would be a time-saver.
>> 
>> If you've got this far in reading, thanks! I know this was a long
>> message, and I hope that I've not wasted too much of anyone's time.
>> 
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