[Tilesathome] What is point of highway=* area=yes?

[D Tucny]

On 18/12/2007, Brent Easton <b.easton at exemail.com.au> wrote:
>
> I'm just interested, are there lists other than tilesAtHome where
> Osmarender changes are discussed? I don't remember this being discussed at
> all. I have no great problem with the change, but it is a major extension to
> the highway tag that has implications (off the top of my head - Map Features
> page,  possible migration to Mapnik,  possible auto-routing issues). It's
> something I thought might have been discussed on this list first?
>
>
As I understand it...
What gets rendered and how it gets rendered typically follows a different
path to things appearing on map features... Often, things will appear on
rendered without being on map features, sometimes even without appearing on
proposed features, also, often things that have made it to map features
won't show up rendered... Typically, this has been due to experimentation in
making the rendered maps look better and improvements in the amount of data
shown by a very small number of people, who, have potentially tagged certain
things and want to see how it'll look on the map while at the same time,
this also partly explains why a lot of things from map features don't appear
as these few only occasionally have time to try to go through map features
and implement new things, typically working on things they've used... Some
other reasons things don't appear rendered are... lack of suitable icons,
map clutter, technical issues etc... Yep, perhaps it could be useful to make
the process more structured, have some update announcements, etc rather than
just svn, there has been some improvement in this area relating to the work
on the server and client software... obviously though, there is a balance
than needs to be achieved... we don't want it to be too difficult for
improvements to happen, but it would be nice to see what was happening :)

One key thing that needs to be remembered though is this... OSM is about the
data, the most important thing is getting the data right, accurately
representing what is on the ground in as much details as possible...
Renderers are just a user of that data and need to take what is there and
turn it into something more human readable...

That said, there has been quite a bit of discussion regarding highway
areas... That was the main reason the area= tag came into existence (see
http://wiki.openstreetmap.org/index.php/Key:area) Things that have come up
as uses for this tag have been... The turning area at the end of a
cul-de-sac/dead end road, often in a residential area... Large
junctions/crossroads/intersections, even small ones... 'Squares'... Toll
areas...

I can see how this tag could be useful, it can in theory 'area enable' any
linear feature... It at first sounds like a primarily rendering related
feature as it's easiest to see how it could make things look better, which
would be a bad thing (not the looking better, but, changing data just for
rendering reasons), but, it can also have it's uses for other things too...
Things I can think of off the top of my head are... User with some form of
navigation device is stood in a square, asks it where they are, 'you are in
blah square' could be the response, with a POI, it would potentially say,
'you are 20m from blah square'... junctions, especially large junctions,
lets say 2 dual carriageways that have bike tracks on each side and traffic
lights for all with all legal turns allowed, the road on the ground isn't a
mesh of crossing lanes, if turning you wouldn't ride/drive to the exact
point that they intersect then perform an on the spot 90 degree turn, they
are typically a large area, routing software could use this... or... the
turning area at the end of a cul-de-sac... You turn into a cul-de-sac by
accident, your satnav asks you to turn around, but, rather than just saying
'where possible', or instructing you to go through someone's house, it knows
the road is narrow (from width) and that there could be parked cars and
tells you there is an area 50m ahead after the right hand bend...

I can also see how it could prove to make some things more difficult... an
area being non-linear and without direction could allow travel in any
direction, in some cases that's not always the case, e.g. tolls... Also, if
linear ways join areas, and new ways start from the other side, routing
software potentially becomes more complex as it going down one street may
involve using many ways and areas instead of a single way that intersects
with others...

I guess, to make it most powerful for all, we'll start seeing some cool
relations based addons... e.g. motorway carries on linearly through tolls,
but, area is also there related to the motorway... junctions have the
addition of the area related to the roads passing through... Then, any
software or features in software that could use the areas could do, any any
software that couldn't wouldn't need to worry about them too much...

d
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