NOAA MBTiles Improvements

[jaybo]

NOAA has published a set of USA charts in the MBTiles format here:
https://distribution.charts.noaa.gov/ncds/index.html

Since there is no way to provide feedback directly to NOAA on these charts, I'm using this DeepZoom Issue to list the problems I've encountered in hope that NOAA will someday notice and implement these improvements.

[jaybo]

Non uniform coverage

Here at zoom 3-4, northern Alaska includes no tiles

[jaybo]

Don't display text and markers at low zoom levels

Here, at zoom 6.2, the buoy and light text is completely illegible. Don't show any markers or text below zoom 7.

[jaybo]

Make depth text slightly larger

MapBox, and presumably most similar tile display engines, displays a given tile over a zoom range. For example a Z14 tile is displayed between zooms 13.5 and 14.5. At the bottom end of this range, particularly on iPhone and similar hires displays, the depth text is almost illegible. Then, as you zoom up to 14.5 it finally becomes large enough, only to shrink again as the zoom increases beyond 14.5.

[jaybo]

Duplication of buoys and cans

This is from Penn Cove, around Coupeville, WA. Presumably the same 2 FL Y 6s is being rendered from two different zoom levels?

[jaybo]

Multiple color values represent land

And the newest NOAA MBTiles release in 2024.05 unfortunately doesn't fix any of the above issues. But it also introduces a new wrinkle. Previously, all of the land areas were a uniform shade of beige. But in the latest release, the land is represented by a range of color values, making the land cutout algorithm unnecessarily difficult: