[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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