[Tagging] Mapping time zones as geometries (relations)

Tue Mar 7 03:01:05 UTC 2017

I agree with deleting the timezone relations.

2017-03-05 21:30 GMT-03:00 Frederik Ramm <frederik at remote.org>:

> Hi,
>
>    I would like to start a discussion about the mapping of time zones.
>
> There are currently 80 relations in OSM tagged as boundary=timezone
> using between them over 10,000 ways.
>
> I think that mapping these time zones as geometries has several issues:
>
> 1. It introduces yet another un-observable object type into OSM. When I
> asked about the source of the data, one person quipped "well you can
> observe it on a local clock", but the people adding time zone boundaries
> don't seem to actually do that - they copy the information from somewhere.
>
> 2. It is for the most part unnecessary noise; almost all time zone
> boundaries run along administrative boundaries, so you could just add a
> timezone tag to the administrative entity instead of mapping a whole
> separate geometry.
>
> 3. It complicates editing; anyone touching one of the aforementioned
> 10,000 ways (which are for the most part also used by admin boundaries)
> will be confronted with the time zone relation and will have to decide
> what to do with it.
>
> 4. It creates very large polygons that may be difficult to edit.
>
> Here's a list of time zones currently mapped in OSM (with relation ID)
>
> 3563652 Московское время
> 3563678 Екатеринбургское время
> 3563726 Красноярское время
> 3563727 Омское время
> 3563885 Иркутское время
> 3563886 Якутское время
> 3563937 Владивостокское время
> 4297465 Самарское время
> 6426325 Cherry County - Chicago TZ part
> 6426796 Idaho Denver TZ part
> 6426797 Idaho Los Angeles TZ part
> 6428675 Alaska - Timezone America/Adak
> 6428690 Alaska - Timezone America/Anchorage
> 6428730 Alaska - Timezone America/Yakutat
> 6428802 Alaska - Timezone America/Juneau
> 6428803 Alaska - Timezone America/Sitka
> 6428944 Canada - Timezone America/Pangnirtung
> 6430296 Malaysia - Kuala Lumpur Timezone
> 6430370 Kiribati - Kiritimati timezone
> 6430371 Kiribati - Tarava timezone
> 6430484 Greenland - timezone America/Danmarkshavn area
> 6430503 Greenland - timezone America/Thule area
> 6430514 Greenland - timezone America/GodThab area
> 6430515 Greenland - timezone America/Scoresbysund area
> 6430658 Хандыгское время
> 6440860 America/Tijuana Timezone
> 6440942 America/Merida Timezone
> 6440955 America/Cancun Timezone
> 6440975 America/Bahia_Banderas Timezone
> 6441066 America/Mazatlan Timezone
> 6442501 America/Mexico_City Timezone
> 6442514 America/Santa_Isabel Timezone
> 6442531 America/Hermosillo Timezone
> 6442686 America/Matamoros Timezone
> 6442687 America/Ojinaga Timezone
> 6442693 America/Chihuahua Timezone
> 6442726 America/Monterrey Timezone
> 6442820 America/Edmonton Timezone part
> 6442821 America/Regina Timezone
> 6442822 America/Winnipeg Timezone part
> 6445625 America/Eirunepe Timezone
> 6445626 America/Manaus Timezone
> 6445682 America/Belem Timezone
> 6445683 America/Santarem Timezone
> 6445860 Asia/Dushanbe Timezone part
> 6446092 Arizona - America/Phoenix Timezone
> 6446108 America/Atikokan Timezone
> 6446109 America/Winnipeg Timezone
> 6446170 America/Cambridge_Bay Timezone
> 6446189 America/Rankin_Inlet Timezone
> 6446190 America/Resolute Timezone
> 6451096 Atlantic/Azores Timezone
> 6451097 Atlantic/Madeira Timezone
> 6451098 Europe/Lisbon Timezone
> 6451458 America/Coral_Harbour Timezone
> 6451459 America/Iqaluit Timezone
> 6483867 Ontario - America/Toronto Timezone
> 6483978 America/Creston Timezone
> 6483979 America/Dawson_Creek Timezone
> 6483980 America/Edmonton Timezone
> 6483981 America/Vancouver Timezone
> 6485969 Asia/Sakhalin Timezone
> 6491030 America/Argentina/Buenos_Aires Timezone
> 6491031 America/Argentina/Catamarca Timezone
> 6491032 America/Argentina/Rio_Gallegos Timezone
> 6491033 America/Argentina/Salta Timezone
> 6491034 America/Argentina/Ushuaia Timezone
> 6491133 Atlantic/Canary Timezone
> 6491134 Europe/Madrid Timezone
> 6491494 America/Chicago Timezone
> 6496417 America/New_York Timezone
> 6496587 America/Indiana/Indianapolis Timezone
> 6496665 America/Boise Timezone
> 6496694 America/Los_Angeles Timezone
> 6498476 America/Menominee Timezone
> 6498563 America/Detroit Timezone
> 6498592 America/Nipigon Timezone
> 6498593 America/Thunder_Bay Timezone
> 6594626 Магаданское время
> 6594635 Камчатское время
>
> And here's them in a map:
>
> http://www.remote.org/frederik/tmp/tz.jpg
>
> Now when you overlay the administrative boundaries on levels 2 and 4,
> only very few lines remain:
>
> http://www.remote.org/frederik/tmp/tz4.jpg
>
> And when you go up to admin level 6:
>
> http://www.remote.org/frederik/tmp/tz6.jpg
>
> Assuming that these boundaries are actually correct, the only places in
> which time zone boundaries don't follow admin boundaries are:
>
> * In South America, the Western boundary of the Manaus timezone and the
> Eastern boundary of the Santarem timezone;
>
> * In North America, the line between the Hermosillo and Santa Isabel
> timezones, the Phoenix timezone, a small part of the boundary between
> the Los Angeles and Boise time zones in Malheur county, the Chicago
> Timezone in Cherry County, a piece of the Los Angeles timezone in Idaho,
> the line between Vancouver and Dawson Creek respectively Creston
> timezones, two incursions into the Regina timezone for Edmonton and
> Winnipeg, two micro timezones called Nipigon and Thunder Bay, as well as
> the Iqaluit and Rankin Inlet timezones far North. (Strangely, around
> Alaske the timezone boundary seems to include a few miles of water that
> are not included in the admin boundary - a quirk in mapping or a quirk
> in time zone definitions?)
>
> As you can see in the images, these lines make up just a fraction of
> time zone boundaries (and it is quite possible that some of these just
> shine up because the matching admin6 boundaries haven't yet been mapped).
>
> I fear that the presence of *some* time zone relations will entice
> people to map even more of them, unnecessarily introducing extra
> geometries into our database when you could easily build time zone
> geometries by either (a) keeping an external database that says "Time
> Zone X consists of the following administrative units" and then
> collecting the units from OSM, or (b) adding a time zone tag to
> adminsitrative entities in OSM - namely, the highest entitiy that still
> has the same time zone which will often be a whole country, sometimes an
> admin-4 entity and very rarely an admin-6 entity.
>
> If there are really some time zone bits and pieces that don't follow
> admin boudnaries (maybe they're marked with signs on the ground
> "caution, wind back your clock all ye who pass here"?) then maybe those
> few bits can be mapped as individual objects... but please, don't
> inflate OSM with time zone geometries just because "it's easier to
> consume that way" (which is the gist from a discussion I had with a time
> zone mapper).
>
> I am worried because with the same reasoning, you could start mapping
> things like "states that have signed up to the XYZ treaty", "states in
> which XYZ is legal/illegal", or anything else. It's a slippery slope,
> and *if* time zones are mapped in OSM at all, I'd rather not have them
> mapped as giant geomtries in their own right, but as properties.
>
> I have recently deleted a few time zone relations in the US and,
> grudgingly, reinstated them because I had to accept that a prior
> discussion was called for. (Changeset discussion here
> https://www.openstreetmap.org/changeset/45644359), and I also requested
> the deletion of
> http://wiki.openstreetmap.org/wiki/Tag:boundary%3Dtimezone which
> prompted verdy_p to write a small novel on the talk page there.
>
> I find the subject of time zones hugely interesting and seeing the
> quirks mapped above has already sent me on a journey reading up on the
> details, but I still think that the mapping of time zones as geometries
> should be discouraged in OSM.
>
> What do you think?
>
> Bye
> Frederik
>
> --
> Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"
>
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-- 
Wille
http://wille.blog.br
http://maption.com.br/
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