[OSM-talk] The Return of the Highway tags and other junk

guy at graviles-reynolds.org guy at graviles-reynolds.org
Mon Dec 18 22:58:20 GMT 2006


Quoting Ben Robbins <ben_robbins_ at hotmail.com>:

> Niko:
> 
> I agree with you post in general.
> 
> Adaption by incorrect tagging is not the best way to go I have now come to 
> think.
> 
> Guy:
> 
> >I have to agree with Andy and Dirk here, as you could by not staying with 
> >the agreed tagging structures find that work hard work is destroyed either
> 
> >by someone indadvertantly deleating it as they updated the map or by an 
> >automated filter purging the dataset of unreognised tags.
> 
> In that case, I shall stay doing it as segments, as I have done this many 
> hundreds of times (est. 500).  The area I edit currently has knowbody else 
> for about 40 miles, So confrontation is yet to be a consern.   Ideally I 
> would like it never to be.   The reason here for staying with nodes seems to
> 
> be cause its easier, not cause its better.  That doesnt stand up to any 
> scutany I'm affirad.
> 
> >I also agree with Dirk that we are mapping the the planet so that it can be
> 
> >navigated
> 
> Yes, I agree mostly, although actually we are making map data that can be 
> used for anything, and how anybody wishes.

True but this can only be achieved by standardisation in the data, using non-
agreed techniques only results in data that only the originator is able to use 
and which is suseptable to purging by automated parsers.
> 
> >not making a scale drawing so that we can recreate it.
> 
> A map is a to scale drawing.  If a person wants to recrete it in a 3d 
> engine, then nothing should stop them.

Maps aren't scale drawings they are pseudo scale pictorial representations of 
topology, that contain compromises to enable their use, this why we are storing 
roads as a series of ways consisting of segments and nodes with associated 
information tags and then rendering them at widiths which are readable at 
various zoom levels and not at the actual scale width. 

> >Coming back to gates and cattle grids, these cannot be represented by 
> >anything else but a node if they are to be used by navigation software 
> >reading the way as they exist as the intersection of two features such as a
> 
> >fence crossing a road.
> 
> Yes I agree that the node has to be connected to the road, so that it can be
> 
> read the by navagation softwere.  This doesnt mean the segments cannot also
> 
> be there.  Its not just navagation softwere that will use maps.  People do 
> to, and im shore theres other reasons.
> 
> >Thus if the fence crosses a road with a cattle grid and you make the cattle
> 
> >grid the correct width and in the fence the road won't see it and vice 
> >versa, either that or you ahve to have a single node at the crossing point
> 
> >as you do now with four short segments radiating from it each with the tag
> 
> >"cattle_grid=yes".
> 
> Yep.  As said in a previous message I tag the node that the road and gate 
> conenct to so the softwear can pick it up.
> 
> >quickest and simplest method of recording and rendering it.
> 
> Its also quickest to make the M1 1 segment long, and have a straight line 
> the entire way.  The quickest way has nothing to do with what is the best 
> way.  Its quality not quantity here.   If 2 methods give the same outcome 
> and 1 is quicker then thats different, but this is not an example of that. 
> 
> 1 node gives less information than a segment, and is contradictory to 
> reality and mapping in general.

In no way is it contradictory, to mapping which is wholly different to reality 
once again you confuse scale drawings and maps. Whilst scale drawings contain 
scale repssentations of features which can be measured both on the drawing and 
relaity, maps contain representional information that can be related from the 
map to reality and back, hence in digital maps a church is a node with data 
attached, which when rendered is a square box with cross for a church with a 
tower, cirle with a cross for a church with a spire and a cross alone for one 
with neither, it is not an outline shown the plan of the church which takes up 
more data space and expresses less information when rendered on the map.

Similarly with creating of nodal information a segements you bloat the dataset 
for no gain to the user.
 
> The only time I would agree with your statment that styles fords and other 
> obsticals should be tagged as nodes, is if they are a large feature and the
> 
> name should appear sperately on the map, like the town name does to a town.
> 
> >When recording gates and cattle grids in features that run parallel to 
> >roads you will obviously have to create a short track off the road and then
> 
> >place the gate/grid node on that rather than on the road itself.
> 
> If you mean where roads split into a grid and gate, along gated roads, then
> 
> the road needs to be split anyway, so I don't understand the problem with 
> that.
> 
> I'm sorry, but I havn't heard 1 point that would make a node seem the 
> logical thing to do.  I have been mapping these feautres for almost a year,
> 
> and this is what Ive come to evaluate as the most succesfful method of 
> recording data.  I would be interested to know the amount of research that 
> has gone into debating the idea of sticking them as nodes.  I will stand 
> corrected if proven wrong, but this really isn't gunna happen at the moment.
> 
>   These points don't seem to stand up to much scrutany. In short If there 
> isnt some rasional agreement, I will just ignore it.
>

Ignoring what is being said is your perogative however don't be surprised if 
the work you have done suddenly disappears out of the dataset, because 
automated purge routines are run to delete non-standard tags which are bloating 
the data set.

Guy





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