Fix Antarctica landcover (#342)

* Fix Antarctica landcover by adding in glacier geometry from Natural Earth. [#337]

Author: wipfli

tiles/src/main/java/com/protomaps/basemap/layers/Earth.java

@@ -9,6 +9,7 @@
 import com.protomaps.basemap.feature.FeatureId;
 import com.protomaps.basemap.names.OsmNames;
 import java.util.List;
+import org.locationtech.jts.geom.Point;
 
 public class Earth implements ForwardingProfile.LayerPostProcesser {
   @Override
@@ -29,6 +30,23 @@ public void processNe(SourceFeature sf, FeatureCollector features) {
     } else if (sourceLayer.equals("ne_10m_land")) {
       features.polygon(this.name()).setZoomRange(5, 5).setBufferPixels(8).setAttr("kind", "earth");
     }
+    // Daylight landcover uses ESA WorldCover which only goes to a latitude of roughly 80 deg S.
+    // Parts of Antarctica therefore get no landcover = glacier from Daylight.
+    // To fix this, we add glaciated areas from Natural Earth in Antarctica.
+    if (sourceLayer.equals("ne_10m_glaciated_areas")) {
+      try {
+        Point centroid = (Point) sf.centroid();
+        // Web Mercator Y = 0.7 is roughly 60 deg South, i.e., Antarctica.
+        if (centroid.getY() > 0.7) {
+          features.polygon("landcover")
+            .setAttr("kind", "glacier")
+            .setZoomRange(0, 7)
+            .setMinPixelSize(0.0);
+        }
+      } catch (GeometryException e) {
+        System.out.println("Error: " + e);
+      }
+    }
   }
 
   public void processOsm(SourceFeature sf, FeatureCollector features) {