Re: [Tagging] lit=yes/no threshold

[Greg Troxel]

Michael Patrick  writes:

> You'd probably be okay using the 10 lux indicated by the Illuminating
> Engineering Society. But considering that the illuminate area is uneven ( a
> notion also covered in the standard ) and usually fairly extensive, and
> illumination measurement is a technical skill, and it is a moving target
> because of the daily cycle and weather, it probably isn't practical o
> expect some member of the general public to collect the data.

Agreed that most mappers cannot measure this, and that all mappers
cannot measure it easily.

About IES and 10 lux: in my town that is considered very high, and in
parking lots beyond what is allowed.  A parking lot that ranges from 0.5
to 3 lux is considered lit.  Average illuminances tend to be 3-4ish, if
built according to our light polllution bylaw.  (I realize that typical
city notions of what is appropriate are different.)


So, saying that something under 10 lux is "lit=no" would not be ok.

I tend to leave the definition alone and not worry that people are
making judgements in marginal cases.  If there are fixtures installed to
light something, and they are doing what was more or less intended, then
it's lit=yes, even if the level is lower than somebody else might like.

To me, marginal cases include:

  there were lights installed but they are now not working well (but
  somewhat).  This is rare enough not to worry about.

  on a walkway in the city, where there are no fixtures intended to
  light the walkway, but due to ambient light from many nearby sources,
  there is a level of 1 lux or more

This second case could arguably be lit=no but it's also dark=no.

I like the suggestion of needing to use a flashlight.   I don't think we
should get too hung up on the edges of subjective.   A notion might be

  Do more than 50% of the users of the path either use a flashlight or
  wish they had one to use.

which is of course fuzzy, but people making that judgement in good faith
are unlikely to have serious arguments.  For cases right on the edge, it
doesn't really matter how they are tagged.

Beyond this, recording illuminance levels makes sense, even though
that's another can of worms.



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[Tagging] lit=yes/no threshold

[Michael Patrick]

> lit=weak is too subjective.
> disclaimer: I am trying to make lit=yes/no definition more precise as
> part of my grant
> https://www.openstreetmap.org/user/Mateusz%20Konieczny/diary/368849

There is a lot of open access academic literature on your topic, covering
objective measures and both subjective indicators and how to derive
objective means from subjective factors. There is also more than a few
international and national design standards, guidelines, and other to form
the basis of your own 'definition'.

For example "Pedestrian and bike path illumination for safety and security:
empirical pre- and  post-field studies by a university team" at
https://www.witpress.com/Secure/elibrary/papers/UT13/UT13060FU1.pdf


You'd probably be okay using the 10 lux indicated by the Illuminating
Engineering Society. But considering that the illuminate area is uneven ( a
notion also covered in the standard ) and usually fairly extensive, and
illumination measurement is a technical skill, and it is a moving target
because of the daily cycle and weather, it probably isn't practical o
expect some member of the general public to collect the data.

However, there is also a considerable work that has been done for measuring
direct and ambient light levels by remote sensing, and correlating those
with on the ground conditions - the only practical way to cover any
significant area since values can be accumulated over time ( by hour to
seasonal ). See
https://ars.els-cdn.com/content/image/1-s2.0-S036013231830550X-fx1_lrg.jpg
and
https://res.mdpi.com/remotesensing/remotesensing-10-01964/article_deploy/html/images/remotesensing-10-01964-g001.png

It still leaves the question how you'd apply any data to a way element - do
you break it into smaller segments to apply differing values as they change
along the route?

Also, what is the specific use case? i.e. is 'lit' really a proxy for some
aspect of safety or reassurance, in which case the illumination level
doesn't matter at all, rather the unevenness, sight lines, and other
factors that affect a (only?) pedestrian's feeling of reassurance and
safety. For instance, no matter how bright a path itself is lit, if that
lighting  produces impenetrable shadows within arms length of my path, it
feels dangerous - an conversely, a unlit wide open field of short grass
feels perfectly safe.

This is a well researched topic, since, like 1285, when English King Edward
I forced property owners to clear highway edges of trees and shrubs. :-)

Michael Patrick
Geographer



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Re: [Tagging] lit=yes/no threshold

[Volker Schmidt]

Just two additional aspects from my own experience on bicycle, to make
things even more complicated:

1) cycle and foot path illumintion dramatically depends on the presence of
leaves on the trees that are planted along the road. (don't get me wrong: I
like trees)

2) another effect which is very annoying and normally completely neglected
by road designers: in many cases cycle paths are being constructed in a way
that you have to pedal against  the car flow on the "wrong" side of the
road, i.e. you get the full blast of the assymmertic headlights of the
oncoming motor vehicles on the main carriageway. Your are effectively blind
even with high level of surface illumination. This is the price you pay two
have two-way cycle paths on one side of the road (which is the desired
situation from the daytime-use point of view).


On Sat, 6 Jul 2019 at 15:05, bkil  wrote:

> In many parts of Hungary, vegetation can overshadow street lights,
> especially if they are placed high enough. They may make efforts to
> protect roads against this, but they rarely consider footways. Hence I
> know a lot of streets where road illumination is fair, but the
> sidewalk right beside it (maybe 1-2m from the road) is dark along the
> majority of the road.
>
> I also agree with Martin's definition of being lit and I usually do it
> like that.
>
> I don't split ways by the centimeter to specify illumination - if a
> stretch of path has too many shadows, you need to bring your own
> lights anyway, so I consider that not being lit.
>
> On Sat, Jul 6, 2019 at 2:39 PM Martin Koppenhoefer
>  wrote:
> >
> >
> >
> > sent from a phone
> >
> > > On 6. Jul 2019, at 14:07, Tobias Zwick  wrote:
> > >
> > > The least subjective definition is to map the physical presence of
> street lanterns on the way, not the light they emit. (This definition
> (though) would mean that a footway close to a lit street would be mapped as
> unlit as long as it does not have own lanterns.)
> >
> >
> > the presence of street lights indicates the road could be lit, it has no
> implications whether it is actually lit. For example last summer I went to
> an island where all streets had relatively new street lights, but half the
> island they kept them off so that light pollution was reduced.
> >
> > In small villages in Germany, street lights are often turned off at a
> certain time (e.g. after 23h), etc.
> >
> >
> > Cheers, Martin
> > ___
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Re: [Tagging] lit=yes/no threshold

[Mateusz Konieczny]

6 Jul 2019, 14:07 by o...@westnordost.de:

>> I am trying to make lit=yes/no definition more precise
>>
>
> I think that your suggestions would make the definition actually less precise 
> because they add a fair level of subjectiveness: "necessary to bring your own 
> light"
>
> The least subjective definition is to map the physical presence of street 
> lanterns on the way, not the light they emit. (This definition (though) would 
> mean that a footway close to a lit street would be mapped as unlit as long as 
> it does not have own lanterns.)
>
This may be less subjective but would be quite pointless - there are many, many 
cases (at least in my city) 
where many footways are well lit without dedicated lanterns.
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Re: [Tagging] lit=yes/no threshold

[bkil]

In many parts of Hungary, vegetation can overshadow street lights,
especially if they are placed high enough. They may make efforts to
protect roads against this, but they rarely consider footways. Hence I
know a lot of streets where road illumination is fair, but the
sidewalk right beside it (maybe 1-2m from the road) is dark along the
majority of the road.

I also agree with Martin's definition of being lit and I usually do it
like that.

I don't split ways by the centimeter to specify illumination - if a
stretch of path has too many shadows, you need to bring your own
lights anyway, so I consider that not being lit.

On Sat, Jul 6, 2019 at 2:39 PM Martin Koppenhoefer
 wrote:
>
>
>
> sent from a phone
>
> > On 6. Jul 2019, at 14:07, Tobias Zwick  wrote:
> >
> > The least subjective definition is to map the physical presence of street 
> > lanterns on the way, not the light they emit. (This definition (though) 
> > would mean that a footway close to a lit street would be mapped as unlit as 
> > long as it does not have own lanterns.)
>
>
> the presence of street lights indicates the road could be lit, it has no 
> implications whether it is actually lit. For example last summer I went to an 
> island where all streets had relatively new street lights, but half the 
> island they kept them off so that light pollution was reduced.
>
> In small villages in Germany, street lights are often turned off at a certain 
> time (e.g. after 23h), etc.
>
>
> Cheers, Martin
> ___
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> Tagging@openstreetmap.org
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Re: [Tagging] lit=yes/no threshold

[Martin Koppenhoefer]

sent from a phone

> On 6. Jul 2019, at 14:07, Tobias Zwick  wrote:
> 
> The least subjective definition is to map the physical presence of street 
> lanterns on the way, not the light they emit. (This definition (though) would 
> mean that a footway close to a lit street would be mapped as unlit as long as 
> it does not have own lanterns.)


the presence of street lights indicates the road could be lit, it has no 
implications whether it is actually lit. For example last summer I went to an 
island where all streets had relatively new street lights, but half the island 
they kept them off so that light pollution was reduced.

In small villages in Germany, street lights are often turned off at a certain 
time (e.g. after 23h), etc.


Cheers, Martin 
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Re: [Tagging] lit=yes/no threshold

[Martin Koppenhoefer]

sent from a phone

> On 6. Jul 2019, at 12:35, Colin Smale  wrote:
> 
> Instead of creating artificial boundaries quantising shades of grey into 
> black and white, why not make it more objective and record the light level in 
> lux on the centre line of the road? Or would it be better to do that on the 
> footpath? That would complicate matters because the two sides of the road may 
> differ.


how would you do this? Usually street lighting is not very homogeneous, 
especially on footways (where the information is most interesting, because 
vehicles bring their own lights anyway), you can only measure the amount of 
light at a single spot, but you will surely get very different measurements 
according to the exact location you choose.

My criterion for pedestrian spaces lit or not would be: can you see dog poo, or 
a hole in the ground? If not it is not (sufficiently) lit.

Cheers, Martin 
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Re: [Tagging] lit=yes/no threshold

[Tobias Zwick]

> I am trying to make lit=yes/no definition more precise

I think that your suggestions would make the definition actually less precise 
because they add a fair level of subjectiveness: "necessary to bring your own 
light"

The least subjective definition is to map the physical presence of street 
lanterns on the way, not the light they emit. (This definition (though) would 
mean that a footway close to a lit street would be mapped as unlit as long as 
it does not have own lanterns.)

Tobias 

On July 6, 2019 12:24:18 PM GMT+02:00, Mateusz Konieczny 
 wrote:
>Some cases of lit=yes are clear (direct lighting of street/footway by
>lamps)
>
>Some cases of lit=no are clear (no lighting whatsoever)
>
>But in cities there is also often strong or weak ambient light, for
>example:
>
>- carriageway is directly lit with so powerful light that spillover
>light
>makes footway well lit - clearly lit=yes
>
>- spillover light is quite dim but enough to comfortably walk - also
>lit=yes
>
>- there is some ambient light, but not enough to walk without own
>source of light - lit=no
>
>- there is an ambient light, one can carefully walk, but only slowly,
>people with poor eyesight needs their own source of light - lit=no (?)
>
>Overall, I am considering adding to
>https://wiki.openstreetmap.org/wiki/Key:lit
>
>recommendation to consider "is it necessary to bring your own light
>source to see it properly"
>as recommended threshold for footways/paths.
>
>Any problems with that or ideas for a better threshold between lit=yes
>and lit=no?
>
>disclaimer: I am trying to make lit=yes/no definition more precise as
>part of my grant
>https://www.openstreetmap.org/user/Mateusz%20Konieczny/diary/368849

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Re: [Tagging] lit=yes/no threshold

[Paul Allen]

On Sat, 6 Jul 2019 at 12:42, Mateusz Konieczny 
wrote:

It is not feasible to do for a typical mapper to record "light level in
> lux".
>

Sadly, however, it is the only objective way of specifying the light
level.  And even then, it's
easy to do it wrong if you don't account for the angle of incidence.  Aim
the sensor at the
light and you'll get a higher reading than if you lay it flat on the ground.

but it is not helping with problem what would be a good threshold between
> lit=yes and lit=no
> on footways
>

In the UK, BS 5266 requires a minimum illumination of 1 lux along the
centre line of
escape routes.  Up until 2011, BS 5266 required a minimum of 0.2 lux along
the centre
line of escape routes.

IIRC, the 0.2 lux figure was approximately equivalent to the light of the
full moon, which
was deemed adequate for some work in shipyards during WW II.  Certainly
it's more
than necessary to take an unhurried stroll along a footpath after your eyes
have
acclimatized to the darkness.  It may be the minimum that was once
considered
adequate to allow evacuation from a dark building after a power cut (no
time for eyes
to acclimatize) but it's not the minimum needed to follow a reasonable
footpath if you're
not in a hurry.

So it is preferable that everyone has their own definition of what is
> lit=no/yes and
> recommend that "in case of doubt is it lit=yes or lit=no feel free to
> choose either"?
>

It's hard for most mappers to accurately measure.  It's hard to agree on a
suitable
figure, because the amount of light necessary depends very much on the
nature of the
path (an asphalted footpath can be safely followed with far less light than
is required for
an unmade path over rocky terrain).  OTOH, if there are lights along the
path, it is clear that it is lit.
If it's the sidewalk of a lit road, it's lit.  In any other cases, it's
probably safer to say it's unlit.

-- 
Paul
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Re: [Tagging] lit=yes/no threshold

[Mateusz Konieczny]

6 Jul 2019, 12:35 by colin.sm...@xs4all.nl:

>
> What problem are you trying to fix here? Usually it is pretty obvious if a 
> street has artificial lighting or not. 
>
>
Unclear desired tagging for footways lit by spillover lighting. As I mentioned 
it is usually obvious
but there are cases where it is not clear.

For example https://www.openstreetmap.org/way/26116023#map=18/50.06730/19.88864 

is path on top of embankment, without own lighting, poorly lit by street lamps 
on a street below it.

Or https://www.openstreetmap.org/way/238304937#map=16/50.0738/19.8891 
 - cycleway
along well lit road but so far away that lighting is poor and faint

Or https://www.openstreetmap.org/way/161706262#map=18/50.05869/19.91701 
 lit only 
by ambient
city light.

In most cases I already tagged something, but it would be nice to check 
whatever it is at least 
sort-of similar to what others would map.

> Instead of creating artificial boundaries quantising shades of grey into 
> black and white, why not make it more objective and record the light level in 
> lux on the centre line of the road?
>
It is not feasible to do for a typical mapper to record "light level in lux".

> Also, don't forget that whether a road is "lit" or not has consequences for 
> traffic regulations, at least in the UK. There is a specific definition 
> associated with this.
>
I found it,

"A road's speed limit is 30 mph (48 km/h) if the road's street lights are "[not 
placed] 
more than 200 yards apart" in England  
and Wales  or "not more than 185 metres" 
in Scotland ;"
https://en.wikipedia.org/wiki/Road_speed_limits_in_the_United_Kingdom#cite_note-80
 


but it is not helping with problem what would be a good threshold between 
lit=yes and lit=no
on footways

>
> My vote is to leave lit=* alone!
>
>
So it is preferable that everyone has their own definition of what is 
lit=no/yes and
 recommend that "in case of doubt is it lit=yes or lit=no feel free to choose 
either"?
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Re: [Tagging] lit=yes/no threshold

[Warin]

On 06/07/19 20:47, Ferdinand Schicke wrote:


What I couldsee work would be to have additional lit=* values like 
lit=weak or lit=spillover or lit=10lux




I tired to use my mobile phone to gauge the amount of night light .. it 
did not work very well at all!


lit=weak is too subjective.

I too would leave lit alone. Either it is lit or it is not.

If you need some measure of 'lit' then I suggest if a map (OSM 
reference) cannot be read by the present light level then it is not lit.




*From: *Mateusz Konieczny <mailto:matkoni...@tutanota.com>
*Sent: *Samstag, 6. Juli 2019 12:26
*To: *Tagging <mailto:tagging@openstreetmap.org>
*Subject: *[Tagging] lit=yes/no threshold

Some cases of lit=yes are clear (direct lighting of street/footway by 
lamps)


Some cases of lit=no are clear (no lighting whatsoever)

But in cities there is also often strong or weak ambient light, for 
example:


- carriageway is directly lit with so powerful light that spillover light

makes footway well lit - clearly lit=yes

- spillover light is quite dim but enough to comfortably walk - also 
lit=yes


- there is some ambient light, but not enough to walk without own

source of light - lit=no

- there is an ambient light, one can carefully walk, but only slowly,

people with poor eyesight needs their own source of light - lit=no (?)

Overall, I am considering adding to 
https://wiki.openstreetmap.org/wiki/Key:lit


recommendation to consider "is it necessary to bring your own light 
source to see it properly"


as recommended threshold for footways/paths.

Any problems with that or ideas for a better threshold between lit=yes 
and lit=no?


disclaimer: I am trying to make lit=yes/no definition more precise as 
part of my grant


https://www.openstreetmap.org/user/Mateusz%20Konieczny/diary/368849



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Re: [Tagging] lit=yes/no threshold

[Ferdinand Schicke]

What I couldsee work would be to have additional lit=* values like lit=weak or 
lit=spillover or lit=10lux

From: Mateusz Konieczny
Sent: Samstag, 6. Juli 2019 12:26
To: Tagging
Subject: [Tagging] lit=yes/no threshold

Some cases of lit=yes are clear (direct lighting of street/footway by lamps)

Some cases of lit=no are clear (no lighting whatsoever)

But in cities there is also often strong or weak ambient light, for example:

- carriageway is directly lit with so powerful light that spillover light
makes footway well lit - clearly lit=yes

- spillover light is quite dim but enough to comfortably walk - also lit=yes

- there is some ambient light, but not enough to walk without own
source of light - lit=no

- there is an ambient light, one can carefully walk, but only slowly,
people with poor eyesight needs their own source of light - lit=no (?)

Overall, I am considering adding to https://wiki.openstreetmap.org/wiki/Key:lit
recommendation to consider "is it necessary to bring your own light source to 
see it properly"
as recommended threshold for footways/paths.

Any problems with that or ideas for a better threshold between lit=yes and 
lit=no?

disclaimer: I am trying to make lit=yes/no definition more precise as part of 
my grant
https://www.openstreetmap.org/user/Mateusz%20Konieczny/diary/368849

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Re: [Tagging] lit=yes/no threshold

[Colin Smale]

What problem are you trying to fix here? Usually it is pretty obvious if
a street has artificial lighting or not. Instead of creating artificial
boundaries quantising shades of grey into black and white, why not make
it more objective and record the light level in lux on the centre line
of the road? Or would it be better to do that on the footpath? That
would complicate matters because the two sides of the road may differ. 

I would say, don't over-engineer the model, and keep it fit for purpose.
The more complexity you add to these rules, the lower the compliance
will be. 

Also, don't forget that whether a road is "lit" or not has consequences
for traffic regulations, at least in the UK. There is a specific
definition associated with this. If you break that link, there will be
another interminable discussion about retagging. 

My vote is to leave lit=* alone! 

On 2019-07-06 12:24, Mateusz Konieczny wrote:

> Some cases of lit=yes are clear (direct lighting of street/footway by lamps) 
> 
> Some cases of lit=no are clear (no lighting whatsoever) 
> 
> But in cities there is also often strong or weak ambient light, for example: 
> 
> - carriageway is directly lit with so powerful light that spillover light 
> makes footway well lit - clearly lit=yes 
> 
> - spillover light is quite dim but enough to comfortably walk - also lit=yes 
> 
> - there is some ambient light, but not enough to walk without own 
> source of light - lit=no 
> 
> - there is an ambient light, one can carefully walk, but only slowly, 
> people with poor eyesight needs their own source of light - lit=no (?) 
> 
> Overall, I am considering adding to 
> https://wiki.openstreetmap.org/wiki/Key:lit 
> recommendation to consider "is it necessary to bring your own light source to 
> see it properly" 
> as recommended threshold for footways/paths. 
> 
> Any problems with that or ideas for a better threshold between lit=yes and 
> lit=no? 
> 
> disclaimer: I am trying to make lit=yes/no definition more precise as part of 
> my grant 
> https://www.openstreetmap.org/user/Mateusz%20Konieczny/diary/368849 
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[Tagging] lit=yes/no threshold

[Mateusz Konieczny]

Some cases of lit=yes are clear (direct lighting of street/footway by lamps)

Some cases of lit=no are clear (no lighting whatsoever)

But in cities there is also often strong or weak ambient light, for example:

- carriageway is directly lit with so powerful light that spillover light
makes footway well lit - clearly lit=yes

- spillover light is quite dim but enough to comfortably walk - also lit=yes

- there is some ambient light, but not enough to walk without own
source of light - lit=no

- there is an ambient light, one can carefully walk, but only slowly,
people with poor eyesight needs their own source of light - lit=no (?)

Overall, I am considering adding to https://wiki.openstreetmap.org/wiki/Key:lit 

recommendation to consider "is it necessary to bring your own light source to 
see it properly"
as recommended threshold for footways/paths.

Any problems with that or ideas for a better threshold between lit=yes and 
lit=no?

disclaimer: I am trying to make lit=yes/no definition more precise as part of 
my grant
https://www.openstreetmap.org/user/Mateusz%20Konieczny/diary/368849
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