[tz] tz dependency lat & lng

Guy Harris guy at alum.mit.edu
Thu Sep 5 22:02:17 UTC 2013

On Sep 5, 2013, at 2:27 PM, random832 at fastmail.us wrote:

> On Thu, Sep 5, 2013, at 17:16, Guy Harris wrote:
>> If all you have is longitude and latitude, you're going to have to do a
>> geometric search.  There might not *be* a place record for where you are,
>> and, even if there is, it won't necessarily have a tag.  They claim to
>> have 105 places tagged with America/New_York; to quote
>> 	https://en.wikipedia.org/wiki/Administrative_divisions_of_New_York
> I don't know why you're quoting that article.

I'm quoting that article because the city with which the tzid is associated is within that state, and fewer neurons had to fire than to choose, for example, the state in which I was born or the state in which I went to institute^Wuniversity.

I'm not quoting any *other* articles because I'm too damn lazy to quote the articles for all the states I listed.

> I suspect the majority of locations tagged with America/New_York are A)
> states that are entirely (or almost entirely) in eastern time and B)
> counties in states that are on the border between it and central time.

Most of them are "relations":


and are probably either:


"multipolygon" or "boundary".  Given that there are 852 relations, that's a lot of counties.

A few are Nodes, which are single points:


and not very useful when solving the "map an arbitrary point to a tzid" unless there are a *LOT* of them, and some are Ways:


which appear to either be paths or small areas.

I'd have to see the data to see what they are, however, and to see whether they're actually useful for the "map an arbitrary point to a tzid" problem (i.e., whether they can be used to define regions corresponding to tzdb zones).

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