Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[OpenStreetmap HADW]

On 7 September 2013 21:41, SomeoneElse  wrote:
> OpenStreetmap HADW wrote:
>>
>> In practice, there is only one renderer for general users
>
>
> That's a statement that could provoke some discussion, I suspect.
>
> If you have a look at the questions on help.osm.org you'll see lots of "why
> doesn't X do Y" type questions, but it isn't always immediately obvious what
> X is. Sometimes it's one of the four main layers on www.osm.org, but if so
> very often it's the Cycle Map rather than the "standard" layer.  Sometimes

Most of these ultimately use Mapnik as the render, and therefore have
its limitation imposed on them.

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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[SomeoneElse]

OpenStreetmap HADW wrote:

In practice, there is only one renderer for general users


That's a statement that could provoke some discussion, I suspect.

If you have a look at the questions on help.osm.org you'll see lots of 
"why doesn't X do Y" type questions, but it isn't always immediately 
obvious what X is. Sometimes it's one of the four main layers on 
www.osm.org, but if so very often it's the Cycle Map rather than the 
"standard" layer.  Sometimes the question is asking about some 
completely different website that uses OSM data, and very often it's 
about a mobile application with no connection to OSM whatsoever except 
that it uses OSM data.  Then there are all the "backgrounds for data 
representation" that use OSM data (http://www.whitehouse.gov/change , 
Apple iOS iPhoto, sundry information boards on poles around the world).


I don't know which is the most-viewed rendering of OSM data (either by 
counting pairs of eyes, or by measuring time).  It's actually a very 
interesting question, but the answer's not straightforward.


Cheers,

Andy


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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[lester]

Sent from my android device so the quoting is crap!

-Original Message-
From: OpenStreetmap HADW 
To: talk-gb@openstreetmap.org
Sent: Sat, 07 Sep 2013 15:07
Subject: Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to 
motor vehicles, open to foot)

On 7 September 2013 14:46, Philip Barnes  wrote:

>
> Streetmaps do tend to be abstractions of the real world, and
> openstreetmap ceased to be be a mere streetmap several years ago, and is
> a far far better map than a mere streetmap can ever be. The word
> streetmap implies urban, cities.


OS maps are abstractions even when not dealing with streets.

The other problems with micro-mapping are:

- the transition between higher and lower levels of abstraction.  I
have considered mapping certain road areas as areas, because the line
approximation loses important information, but,  unless a road joins
an area perpendicularly, this doesn't work well in the transition
region;

- with things like sidewalks, there is usually a fixed distance
between the two pedestrian ways and the vehicle way, but the current
data structure cannot represent that, and the current tooling doesn't
support it very well, so if everyone started mapping sidewalks
explicitly, there would be big maintenance problems (I've just seen a
transition case where a road both has a separate footpath, with cycle
access and the road itself is marked as having parallel cycle tracks);

- routing software can no longer just operate on a network of edges
and nodes, but needs to know that your can normally cross from one
sidewalk to the other, at arbitrary places. (currently I have seen
explicit footway crossings, where no physical features exists, being
inserted to get round this one.  Basically, the abstraction is adding
value, by showing that the the sidewalks are related.

Trying to incorporate all of the conditions relating to the physical structure 
of the road using just tags would make things almost impossible to understand. 
With the level of detail becoming available for buildings, adding the footpaths 
through developments is accepted, and those around the edge add value simply by 
showing their presence. YES routers need a bit more inteligence, and in cities 
with barriers between car and pedestrian, things are simple. A 'clever' foot 
router could be made to recognise that people can walk anywhere in shopping 
precincts, so why not the area of a footpath/road combination?
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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[lester]

Long time discussion but the data is not the map. If a detail is need, such as 
adding a way to show the pedestrian route around an object, then it should be 
mapped. Not mapping it leaves gaps in the data. Now replacing the obstruction 
with a short length of 'footpath' may be an alternative, but knowing the detail 
of some of the type of street being mapped, there are alternative footpaths 
which do not join naturally to the vechical sections, but do to additional 
footpaths alongside. One would take a wheelchair 'around' via another route.

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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[OpenStreetmap HADW]

On 7 September 2013 14:36,   wrote:
> Sent from my android device so the quoting is crapp!
>
>
> -Original Message-
> From: OpenStreetmap HADW 
> To: talk-gb@openstreetmap.org
> Sent: Sat, 07 Sep 2013 13:44
> Subject: Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to
> motor vehicles, open to foot)
>
> On 7 September 2013 12:15, SomeoneElse  wrote:

>
> Then it is up to the rederers to make any simplificatons needed

In practice, there is only one renderer for general users, and my
impression is that that doesn't have that much deep understanding, so
relies on conventional mapping abstractions and a lot of user provided
rules.

Although technical users may use special renderers for special tasks,
to be generally useful, the map has to provide as much useful
information to the user as possible using a relatively simple minded
renderer.

(I did actually chance on a paper discussion how Mapnik's placing and
selection of labels is far from ideal, which is probably one of the
more difficult things that it actually tries to do.)

The maps also have to work with mappers who don't understand the
difference between the rendered map and the internal representation,
so will not provide the rich metadata needed for an intelligent
renderer (as mentioned on another thread, they will load the map with
footpaths and car parks, but not add the access=* tags needed to
distinguish between those that can and cannot be used).

If a render tries to get too clever on data that doesn't have
consistent and rich meta-data, it is likely to guess wrong and
introduce artefacts as a result.  That's OK if the result will be
cleaned up by a human, the machines will have done a lot of let work,
but that is not the case here.

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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[OpenStreetmap HADW]

On 7 September 2013 14:46, Philip Barnes  wrote:

>
> Streetmaps do tend to be abstractions of the real world, and
> openstreetmap ceased to be be a mere streetmap several years ago, and is
> a far far better map than a mere streetmap can ever be. The word
> streetmap implies urban, cities.


OS maps are abstractions even when not dealing with streets.

The other problems with micro-mapping are:

- the transition between higher and lower levels of abstraction.  I
have considered mapping certain road areas as areas, because the line
approximation loses important information, but,  unless a road joins
an area perpendicularly, this doesn't work well in the transition
region;

- with things like sidewalks, there is usually a fixed distance
between the two pedestrian ways and the vehicle way, but the current
data structure cannot represent that, and the current tooling doesn't
support it very well, so if everyone started mapping sidewalks
explicitly, there would be big maintenance problems (I've just seen a
transition case where a road both has a separate footpath, with cycle
access and the road itself is marked as having parallel cycle tracks);

- routing software can no longer just operate on a network of edges
and nodes, but needs to know that your can normally cross from one
sidewalk to the other, at arbitrary places. (currently I have seen
explicit footway crossings, where no physical features exists, being
inserted to get round this one.  Basically, the abstraction is adding
value, by showing that the the sidewalks are related.

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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[Philip Barnes]

On Sat, 2013-09-07 at 13:43 +0100, OpenStreetmap HADW wrote:
> On 7 September 2013 12:15, SomeoneElse  wrote:
> 
> >
> > In that instance isn't there effectively a short footway that runs parallel
> > to the short piece of road that has the barrier on it?
> >
> Micro-mapping tends to clutter the rendered map.  In any case, street
> maps are abstractions of the real world and do deliberately simplify.

Streetmaps do tend to be abstractions of the real world, and
openstreetmap ceased to be be a mere streetmap several years ago, and is
a far far better map than a mere streetmap can ever be. The word
streetmap implies urban, cities. 

In many way I do wish a different name had been chosen, when trying to
wean friends and colleges off google and onto OSM I do find the word
streetmap is a perceptive barrier to acceptance as they then assume and
A to Z and not something rivaling, and exceeding, OS maps, that can
allow you to walk in the countryside and show hedges and stiles. 

In the UK we have all grown up with high quality mapping and obviously
we are not going to be content to stop short of that. 

Phil (trigpoint)



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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[lester]

Sent from my android device so the quoting is crapp!

-Original Message-
From: OpenStreetmap HADW 
To: talk-gb@openstreetmap.org
Sent: Sat, 07 Sep 2013 13:44
Subject: Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to 
motor vehicles, open to foot)

On 7 September 2013 12:15, SomeoneElse  wrote:

>
> In that instance isn't there effectively a short footway that runs parallel
> to the short piece of road that has the barrier on it?
>
Micro-mapping tends to clutter the rendered map.  In any case, street
maps are abstractions of the real world and do deliberately simplify.

Then it is up to the rederers to make any simplificatons needed - you do not 
map for them !!! OK agreeing on how things simplify may need to be agreed, but 
that is a different problem.
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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[OpenStreetmap HADW]

On 7 September 2013 12:15, SomeoneElse  wrote:

>
> In that instance isn't there effectively a short footway that runs parallel
> to the short piece of road that has the barrier on it?
>
Micro-mapping tends to clutter the rendered map.  In any case, street
maps are abstractions of the real world and do deliberately simplify.

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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[lester]

Sent from my android device so the quoting is crap!

-Original Message-
From: SomeoneElse 
To: "talk-gb@openstreetmap.org" 
Sent: Sat, 07 Sep 2013 12:16
Subject: Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to 
motor vehicles, open to foot)

OpenStreetmap HADW wrote:
> I keep coming across cases where marking the access to a way based on
> primary category will imply that the way is not suitable for use on
> foot.  That becomes particularly interesting with barriers, as in
> those cases, the sidewalk may bypass the barrier.
>

In that instance isn't there effectively a short footway that runs 
parallel to the short piece of road that has the barrier on it?

Micro mapping would add the 'sidewalks' as separate ways and ideally that is 
the way forward, but there are still roads where foot traffic share the blocked 
vehical way ...
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Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[SomeoneElse]

OpenStreetmap HADW wrote:

I keep coming across cases where marking the access to a way based on
primary category will imply that the way is not suitable for use on
foot.  That becomes particularly interesting with barriers, as in
those cases, the sidewalk may bypass the barrier.



In that instance isn't there effectively a short footway that runs 
parallel to the short piece of road that has the barrier on it?


Cheers,

Andy


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[Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)

[OpenStreetmap HADW]

I keep coming across cases where marking the access to a way based on
primary category will imply that the way is not suitable for use on
foot.  That becomes particularly interesting with barriers, as in
those cases, the sidewalk may bypass the barrier.

For concrete examples, I'll use Northwick Park and Northwick Part Tube
station, in North West London.

At the North end, there is a stub road
.  This is gated off,
almost permanently, where it joins the local public road, but has
sidewalks and there are gaps in the barrier for each sidewalk.

At the station end, it leads to a permanently open foot tunnel, which
exits to Proyer's Path, which is signposted as mixed foot and cycle,
and was recently re-laid explicitly to make it suitable for mixed use.
 There are also foot routes into Westminster University and Northwick
Park Hospital, from the end of the tunnel.

It seems to me that the stub road has private status for motor
vehicles, and as it is in the form of a road for such vehicles, that
is its primary status.  Is must have destination status on foot and
dismounted bicycles, for the tube station.  The junction with Proyers
Path suggests that it should have at least yes status for foot and
cycle.

At the moment, I've coded it as access=private; foot=yes, which should
result in correct routing decisions, but will cause it not to show as
passable to pedestrians on normal map renderings.

The gate is more of a problem, as my reading of the access rules for
gates is that they specify what can pass when the gate is open, so
don't allow you to specify categories for which the gate effectively
doesn't exist (pedestrians, in this case).  Gates possibly need a way
of indicating types of traffic for which they are really entrances.
(Possibly foot=entrance, or, with more backward compatibility
problems, motor_vehicle=gate.)

At the other end of Proyers path, is a car park, and a roadway leads
South from there, to another gate
, which is open to
authorised vehicles only (as signed on the driveway, beyond the gate,
so really not an attribute of the gate).  The gate is bypassed by
people on the pavement on the public road, but is open from 8am to
nominal dusk.  To add complications, just inside the gate is a PROW
public footpath sign, for a footpath to the park, so, although the
scope of this is very unclear, the bypass probably has PROW status.

Authorised vehicles are, I suspect, ones using the pavilion, by the
car park, but the main reason is probably to stop its use as a station
car park, by long distance commuters.

The road has cycle markings, so there is some presumption that it is
always open to cycles.

If I mark the gate with opening hours and access, it implies these
restrictions apply to pedestrians and cyclists, which they don't.  If
I mark the driveway as private or destination, it will be shown as
that on the standard map, even if the restriction is removed by the
use of foot and cycle keys.

Whilst one could break out the sidewalk paths on each side of the
gate, as explicit features, that will clutter the map (as a side note,
I already see some areas of the map being cluttered by having every
private path and car park).  It doesn't help with the driveway through
the park, as that has no sidewalks, once you get past the gate.

What are peoples thoujghts on the best way of getting the data model
correct, whilst also producing something useful to people using the
standard map rendering, particularly for barriers.

PS There are yellow padlocks on the second gate, so even the opening
hours are not valid for emergency vehicles.

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