[Tagging] Mapping time zones as geometries (relations)

Jaroslav KamenĂ­k jaroslav at kamenik.cz
Tue Mar 7 11:42:02 UTC 2017

Hi all,

this discussion has started because of me, so I would like to add few

Should OSM contains timezone data? I think so. Some said, we should use other
sources and overlay them over OSM, but there is no direct mapping except
description in human languages, not too usable for computer. Other thing is that
available map sources use different shapefiles, so they are not aligned to OSM.
You know, I would like to see Prague timezone in my navigation walking along
Czech borders.:)

Should we use extra geometries for timezones? As Frederik wrote, there
are 80 timezone relations now.
There is about 850 other relations tagged with timezone attribute, so
timezone relations are just fraction
of the whole amount and I am not afraid that their amount will grow
(too much). Why? Timezone relations are used
in places where timezone border goes by river/meridian/territorial
waters or to split big countries instead
of tagging hundreds of counties/.... We can eliminate some (most?) of
them, but not all of them. Btw. timezone tags
can be misused too - for example - I removed useless timezone tags
from hundreds of small relations in Germany during
timezones editation, there was tag at whole country, and at lots of
admin boundaries too.

Some wrote that timezones are changing. Yes, all OSM are still
changing, shops, bus stops, new buildings, forrests
cutted, we all do such editations often I think...

Some wrote that timezones are not visible. Yes, exactly as lots of
other data in OSM.

Some wrote - delete timezone relations! Thanx, guys, it took lots of
time and work to create them...

So, for me, as you can guess, timezone relations are good and usefull
solution, but I understand that there could be
problems with their sizes and dependence to other geometry. Personally
I would compromise - leave timezone relations
where really needed (river/meridian/territorial waters/...) and change
them to tagged A.B. otherwise.

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