[Talk-us] admin level for US states

Minh Nguyen minh at nguyen.cincinnati.oh.us
Mon Nov 24 20:18:55 UTC 2014


On 2014-11-24 05:00, Martin Koppenhoefer wrote:
> I wonder why US States are tagged as admin_level=4, wouldn't it be more
> consistent with the rest of the map to have them tagged as level 3?

IIRC mappers in many regions of the world started out using 
even-numbered admin_levels only, skipping the odd numbers, so that more 
obscure groupings of jurisdictions could be inserted in the future 
without going fractional. And indeed, if you look at [1], admin_level=3 
has been used primarily for "regions": groups of provinces that have no 
separate administrative authority. Assuming this table reflects the 
actual state of the map, most countries have chosen 4 for their state 
equivalents.

This level-skipping scheme extends all the way down to the smallest 
jurisdictions. Because the TIGERcnl import chose admin_level=8 for 
municipalities, skipping 7, I was able to tag Ohio townships as 7 
without demoting all the state's cities and villages. [2] Even though 
neighboring Kentucky and West Virginia lack a level of government 
between counties and municipalities, it makes sense to keep cities in 
most states at the same admin_level, because they're functionally 
equivalent. (Virginia is a notable exception.)

For context, there's an open pull request to have the Standard 
stylesheet render country and state labels based on administrative 
boundary polygons rather than place nodes. [3]

Martin, how would the U.S. would be affected by this change? As it 
stands, U.S. state boundaries and labels appear at z4 and above, 
regardless of the state's size. Of the smallest states, Rhode Island 
(RI) appears at z4 and z6+, Connecticut (CT) appears at z4+, and 
Maryland (MD) and Delaware (DE) are both obscured at z4 by the label for 
Washington, D.C.

At a glance, this change would seemingly omit most of the Northeastern 
states' labels at z4. It appears to set a minimum size of 750 "way 
pixels" at z4 and 3,000 at z5 for displaying a state's label. I don't 
really see those states' two-letter refs as being clutter. They're 
probably the most informative use of that space at z4 in a big country 
like the U.S. Unfortunately, they really clutter up the map in smaller 
countries, especially in Europe.

[1] http://wiki.osm.org/wiki/Tag:boundary%3Dadministrative
[2] http://wiki.osm.org/wiki/United_States_admin_level
[3] https://github.com/gravitystorm/openstreetmap-carto/pull/1134

-- 
minh at nguyen.cincinnati.oh.us




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