[Tagging] Tagging Digest, Vol 43, Issue 6, Tagging city details, message 4

St Niklaas st.niklaas at live.nl
Sun Apr 7 20:52:01 UTC 2013


> From: tagging-request at openstreetmap.org
> Subject: Tagging Digest, Vol 43, Issue 6
> To: tagging at openstreetmap.org
> Date: Sun, 7 Apr 2013 18:59:06 +0000
> 
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> Message: 4
> Date: Sun, 07 Apr 2013 11:37:20 -0700
> From: Martin Atkins <mart at degeneration.co.uk>
> To: tagging at openstreetmap.org
> Subject: [Tagging] Mismatched Level of Detail in highways vs. other
> 	elements
> Message-ID: <5161BCE0.7060905 at degeneration.co.uk>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> 
> Hi all,
> 
> I do mapping in San Francisco, CA and I'm frustrated about the 
> inconsistent levels of detail we typically use when mapping urban 
> environments.
> 
> For example, most highways are mapped in a network-oriented fashion with 
> one string of ways representing both directions of traffic, often 
> encapsulating other features like cycle lanes and sidewalks, and 
> intersections simply represented by crossing the streets at a single 
> common node.
> 
> On the other hand, rail lines are most commonly mapped by their physical 
> shape, so the rail ways come in pairs. The people who mapped the tram 
> lines in San Francisco also mapped the curves of the rails at 
> intersections, rather than having them meet at a single node as with the 
> highways. This creates the following ridiculous effect in rendering:
>      http://osm.org/go/TZHvFT5aF--
> 
> Notice how the rails only just fit inside the rendered street on 
> straight sections, and cut the street corner completely at the intersection.
> 
> However, here's how it actually looks on the ground (looking across the 
> intersection from east to west). Notice that the rails are completely 
> contained within this 4-lane intersection (all four being normal traffic 
> lanes with no physical separation except for the tram boarding platforms):
>      http://oi45.tinypic.com/w6qsgh.jpg
> 
> (On the plus side, we're doing better than Google Maps, whose rendering 
> makes it look like the rails on Church street are both off to the west 
> side of the street! http://tinyurl.com/cedot4n )
> 
> This problem shows up in various other contexts too: it's impossible to 
> accurately tag a bench or bus stop on a sidewalk because the sidewalk 
> doesn't exist as a separate construct. Fences or buildings directly abut 
> the street end up rendering either over the street or set back from it 
> because the true width of the street is not represented.
> 
> For most normal street mapping and vehicle routing purposes it seems 
> sufficient to just know simple landmark details that aid in orientation, 
> e.g. that whether particular street contains a railway or it passes 
> alongside a railway. Of course, more detail-oriented uses like 3D 
> renderings it'd be more important to have the full physical street 
> layout described, with separated lanes and proper physical relationships 
> with surrounding objects.
> 
> How have others resolved this fundamental conflict? More detailed 
> streets, or less-detailed everything else?
> 
 Hi Martin, Isn’t mapping the same as making choices, what to do or not ? From 1:1.000.000 up to 1:25.000, from less to lots off it, but it’s getting easier since were mapping digital. If we don't make detailed choices, results wont get perfect. Just tag the situation large and shrink it back again.And yes the choice is between detailed maps or fuzzy ones, it comes with a lot of extra work !Greetz
 		 	   		  
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