Small osm_admin boundaries should not render at low zooms

[clhenrick]

When looking at Seattle I noticed an odd artifact at #10/47.1159/-122.0821. On zooming in it turns out to be a small tribal administrative boundary. We should probably add a query that prevents small admin areas from rendering at low zooms so we don't end up with black specs on the map.

Notice the speck below Prairie Ridge

Identified in QGIS:

[almccon]

Good point. Indian Reservations in OSM are extremely poorly mapped (a project for another day), but we should try to handle them correctly in case more get added. Is it black because that's the correct style for admin boundaries at that zoom, or is it black because we failed to completely apply a style to that feature?

[clhenrick]

Not sure, feel like I've noticed this pattern (dashed black lines) elsewhere so will look more closely for where it is or is not coming from.

[clhenrick]

Looks like we are switching from NE admin boundaries to OSM boundaries at zoom 10 but with nothing to filter out small administrative areas at high zooms. Would calculating area for a filter make sense as a way to resolve this? Or perhaps doing a ILIKE '%reservation%' on name?

[clhenrick]

It appears that Indian Reservations fall within the admin_level = 4 query in the .yaml files. Perhaps calculating an area field in the osm_admin table is the best bet. That way we can filter out really small admin areas at lower zoom levels but still show them at higher zooms.

[clhenrick]

Fixed via commit 1403967

[almccon]

Looks like this requires we run osm_admin_area.sql during database setup? I'll add that to the Makefile

[clhenrick]

Ah yeah it does, I had assumed the make file executes whatever lives in sql/functions/ when creating a db.

-Chris L Henrick

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On Mon, Oct 26, 2015 at 1:58 PM, Alan McConchie notifications@github.com wrote:

Looks like this requires we run osm_admin_area.sql during database setup? I'll add that to the Makefile

— Reply to this email directly or view it on GitHub https://github.com/stamen/terrain-classic/issues/39#issuecomment-151227575 .

[almccon]

There are a ton of admin_level = 4 boundaries in Switzerland, and it still looks messy. Dotted-line boundaries are a pain, because when you've got overlapping borders the dotted lines get out of sync, so it ends up looking almost solid sometimes.

I'm going to tone them down some more, at least.

[clhenrick]

Ah, good catch. I agree using the lighter boundary style would be an improvement for these.