Ocean Layer Not Rendering at Low Zoom Levels in PMTiles (GeoServer)

[ronitjadhav]

Problem

When serving PMTiles generated by shortbread-tilemaker through GeoServer using the PMTiles extension and MBStyle, ocean polygons do not render at zoom levels 0–7.

This happens because GeoServer relies on PMTiles layer metadata to decide which layers are available at a given zoom level.

---

Root Cause

In config.json:

• The ocean layer is defined with:

  "minzoom": 8
  

• The ocean-low layer covers zooms 0–7 and writes into ocean:

  "minzoom": 0,
  "maxzoom": 7,
  "write_to": "ocean"
  

While tilemaker correctly merges ocean-low geometries into the ocean layer at zooms 0–7, PMTiles metadata only reflects the primary layer definition, resulting in:

"ocean": { "minzoom": 8, "maxzoom": 14 }

GeoServer (via the PMTiles extension) therefore assumes the ocean layer does not exist below zoom 8 and does not render it, even though the tile data contains valid ocean polygons.

---

Solution

Update the ocean layer definition to match the actual data range after merging:

"ocean": {
-  "minzoom": 8,
+  "minzoom": 0,
   "maxzoom": 14,
   ...
}

This ensures PMTiles metadata correctly advertises ocean data at all zoom levels, allowing GeoServer + MBStyle to render it correctly.

---

Testing

• Generated PMTiles for the Europe region

• Verified metadata now reports:

  "ocean": { "minzoom": 0, "maxzoom": 14 }
  

• Confirmed ocean renders correctly at low zoom levels in GeoServer using the PMTiles extension and MBStyle

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Visual Comparison

Before	After

[danduk82]

👍 for this update