Park boundaries should trump landcover data at higher zooms

[clhenrick]

Looks like with the new terrain-classic park boundaries aren't being rendered and that the landcover data is displaying at high zoom levels.

There must be a rule in cascadenik for the og terrain tiles that decides when to swap landcover data for park boundaries as the polygon layer to composite onto the hillshades.

Looks like at zoom 10 park boundaries start showing up, possibly on top of dimmed landcover data? Then at zoom > 10 park boundaries are more definitive.

[clhenrick]

On further inspection it seems that park boundaries are being drawn but the landcover styling is over powering them.

[clhenrick]

We might want to dissolve the osm green areas at low zoom levels as overlapping polygons create darker areas due to the transparency. Or could we solve this with a polygon-comp-op?

[clhenrick]

"Dissolving" the polygons for higher zooms seems to solve the problem of overlapping park boundaries but I'm not sure if this would work for a planet file as it merges all the parks into one polygon. Perhaps grouping by type would be a better method?

CREATE TABLE osm_green_areas_z13_dissolved AS (
SELECT ST_Union(geometry) as geometry, 
SUM(area) as area,
type
FROM osm_green_areas_z13
GROUP BY type
);

Any thoughts @almccon @seth?

[clhenrick]

I'm noticing that in the OG terrain the style for parks with larger areas may have been made more transparent and had their borders blurred while smaller parks were given a more opaque fill and solid borders.

Notice Tilden Golf Course to the lower left and the area around the reservoir to the middle top, while the rest of the green area is a lighter shade and fades out along its border to the lower left:

[clhenrick]

Proposed solution:

• forget about dissolving park areas for higher zooms
• instead ditch the polygon-opacity and use polygon-comp-op: src;

This seems to dissolve the overlapping park boundaries as well as provide a blending with the terrain underneath.

Here is a screen shot from TileMill showing the dissolved overlapping boundaries:

And here is a screen shot from Tessera running with the very pixellated hillshade underneath:

The only to-do will likely be tweaking the osm-green-areas color to make it a little less obtrusive when the final tiles are rendered.

[almccon]

Nice. Works for me. I agree we might want a color tweak, but the composite effect looks great.

[clhenrick]

:+1: