Modeling OSM sidewalk data

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Modeling OSM sidewalk data

Paul Norman
I'm working on putting OSM sidewalk data into PostgreSQL with
ClearTables (https://github.com/ClearTables/ClearTables/issues/39) and
looking at two different ways, and wondering if anyone has experience
modeling it.

There are two obvious options

1. Have a sidewalk column with an enum type with both/left/right/neither

2. Have sidewalk_left and sidewalk_right boolean columns

I can see advantages and disadvantages to both.

Does anyone have experience consuming OSM sidewalk data and have
thoughts about what would be better to work with?

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Re: Modeling OSM sidewalk data

Darafei "Komяpa" Praliaskouski
Hi Paul,

Both ways are only applicable to cities with blocky structure.
In ex-USSR, architecture of cities is different, and footways / sidewalks graph is more complicated than a replica of roads for cars, so all the sidewalks have to be drawn separately.


вт, 12 июл. 2016 г. в 10:45, Paul Norman <[hidden email]>:
I'm working on putting OSM sidewalk data into PostgreSQL with
ClearTables (https://github.com/ClearTables/ClearTables/issues/39) and
looking at two different ways, and wondering if anyone has experience
modeling it.

There are two obvious options

1. Have a sidewalk column with an enum type with both/left/right/neither

2. Have sidewalk_left and sidewalk_right boolean columns

I can see advantages and disadvantages to both.

Does anyone have experience consuming OSM sidewalk data and have
thoughts about what would be better to work with?

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Re: Modeling OSM sidewalk data

dieterdreist


sent from a phone

> Il giorno 12 lug 2016, alle ore 11:15, Komяpa <[hidden email]> ha scritto:
>
> Both ways are only applicable to cities with blocky structure.
> In ex-USSR, architecture of cities is different, and footways / sidewalks graph is more complicated than a replica of roads for cars, so all the sidewalks have to be drawn separately.


There are sidewalks (alongside roads) and other footpaths, just like everywhere else (but in different proportions). You can decide to draw the sidewalks separately or not (like anywhere else), while you have in any case to draw the independent footways with their own geometry.

cheers,
Martin
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Re: Modeling OSM sidewalk data

Andy Townsend
In reply to this post by Paul Norman
On 12/07/2016 08:42, Paul Norman wrote:
> Does anyone have experience consuming OSM sidewalk data and have
> thoughts about what would be better to work with?

Rather than having sidewalk data available in a column, I instead with a
different highway value for "this road has a usable sidewalk".  We
already have a plethora of highway values, so the extra work to support
isn't high, and has the advantage that you don't need to mess about with
the schema (though you do need to reload the database) if anything changes:

https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L258

My initial goal was to be able to render sidewalks on unclassified and
tertiary roads.  Note that there are more values in that list than
you're probably expecting - that was what was found to be in the data
when I looked locally.  Here's a diary entry, with a picture of what
things look like

http://www.openstreetmap.org/user/SomeoneElse/diary/38136

(though I've tidied up the rendering a bit since then).

To address Komяpa's point, it's absolutely true that mapping sidewalks
as separate ways is something that you need to consider in some cases
(though I'd dispute that it is "only applicable to cities with a blocky
structure" - sidewalk=both et al mostly work well in the UK).  In some
places (e.g. in my experience Helsinki) sidewalks meander off on their
own and then rejoin roads, and separate mapping makes sense.  Also, if
you're mapping dropped kerbs etc. for wheelchair use then it's a lot
easier to map sidewalks separately.

Unfortunately, the biggest problem with "sidewalks mapped as separate
ways" is that they sometimes tend not to be done very well - often the
mappers produce something that looks nice on a printed map but doesn't
represent the topology (by no means always, but often enough to be an
issue).  For example (not far from Komяpa's link) I very much doubt that
this shows a correct foot route between the highlighted places:

https://www.openstreetmap.org/directions?engine=graphhopper_foot&route=53.94458%2C27.72384%3B53.94459%2C27.72419#map=19/53.94428/27.72472

The road that these are the sidewalks of
https://www.openstreetmap.org/way/281594594 has no sidewalk information
(though in this case, being a living_street, you should be safe walking
along the middle of the road).

 From the readme of https://github.com/ClearTables/ClearTables it sounds
like you're trying to process OSM data as it actually exists, not "as it
ought to be tagged", which means you might have to do something "clever"
to detect poorly mapped examples like the one above, perhaps based on
proximity.  I'd be interested to see what you come up with...

Best Regards,

Andy



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Re: Modeling OSM sidewalk data

Paul Norman
In reply to this post by Darafei "Komяpa" Praliaskouski
On 7/12/2016 2:15 AM, Komяpa wrote:
>
> Both ways are only applicable to cities with blocky structure.
> In ex-USSR, architecture of cities is different, and footways /
> sidewalks graph is more complicated than a replica of roads for cars,
> so all the sidewalks have to be drawn separately.

Yes, I should of been clearer, sidewalks in this context are highways
tagged with a sidewalk=* tag.

It does bring up the question of how to handle something like
highway=footway sidewalk=right - a footway with a sidewalk.

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Re: Modeling OSM sidewalk data

Paul Norman
In reply to this post by Andy Townsend
On 7/12/2016 3:44 AM, Andy Townsend wrote:

> On 12/07/2016 08:42, Paul Norman wrote:
>
> Rather than having sidewalk data available in a column, I instead with
> a different highway value for "this road has a usable sidewalk".  We
> already have a plethora of highway values, so the extra work to
> support isn't high, and has the advantage that you don't need to mess
> about with the schema (though you do need to reload the database) if
> anything changes:
>
> https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L258 
>

Don't you quickly start needing to have many many values for your
highway column as you combine sidewalks, link status, cycleways, etc?

For me a sidewalk column is much easier to do than expand the highway
class values and it avoids users downstream of me having to deal with
sidewalks if they're not using them in their analysis or rendering.

> My initial goal was to be able to render sidewalks on unclassified and
> tertiary roads.  Note that there are more values in that list than
> you're probably expecting - that was what was found to be in the data
> when I looked locally.

I also see you're treating cycleways as sidewalks. I'm planning on
handling them separately, which is another reason I'm using more columns.

> From the readme of https://github.com/ClearTables/ClearTables it
> sounds like you're trying to process OSM data as it actually exists,
> not "as it ought to be tagged", which means you might have to do
> something "clever" to detect poorly mapped examples like the one
> above, perhaps based on proximity.  I'd be interested to see what you
> come up with...

I'm dealing with "tagging as it exists", which is slightly different
than "data as it exists", so I don't have to worry about data errors
like those disconnected ways. This is partially due to technical
constraints, but even without them I'm not sure if I'd handle that case.

It's also going to a PostGIS database so there's no notion of if two
linestrings are connected, only if they're touching.

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Re: Modeling OSM sidewalk data

Oleksiy Muzalyev
In reply to this post by dieterdreist
On 12.07.2016 11:24, Martin Koppenhoefer wrote:

>> Il giorno 12 lug 2016, alle ore 11:15, Komяpa <[hidden email]> ha scritto:
>>
>> Both ways are only applicable to cities with blocky structure.
>> In ex-USSR, architecture of cities is different, and footways / sidewalks graph is more complicated than a replica of roads for cars, so all the sidewalks have to be drawn separately.
>
> There are sidewalks (alongside roads) and other footpaths, just like everywhere else (but in different proportions). You can decide to draw the sidewalks separately or not (like anywhere else), while you have in any case to draw the independent footways with their own geometry.
>
> cheers,
> Martin
>
To understand an architecture of a city, especially of a sidewalks
system, we should realize that it was formed to a large degree by the
auto industry lobbying [1]. Obviously, in North America and Western
Europe this process began several decades earlier than in Eastern
Europe, so sidewalks and footpaths system is indeed somewhat different.


However, an emerging global trend of Walkable Development is starting to
transform cities once again [2].


[1] "Creeps and Weirdos: the auto industry agenda for keeping you on
four wheels"

http://www.preventioninstitute.org/about-us/lp/800-creeps-and-weirdos-the-auto-industry-agenda-for-keeping-you-on-four-wheels.html

[2] KC Conspiracy Theorists: Walkable Development Will “Devastate” Auto
Giants

http://usa.streetsblog.org/2016/05/24/kc-conspiracy-theorists-walkable-development-will-devastate-auto-giants/


Best regards,

Oleksiy



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