Add OSM elevation to point POIs (#619)

* Add OSM elevation to point POIs

Natural peak features are usually OSM point features, but the POI layer only copied the OSM ele tag while building the named-polygon point-on-surface output. That meant point peaks were emitted without the elevation attribute even when the source feature had ele set.

Move the elevation assignment into the common POI attribute chain so all OSM POIs can carry ele through to the output feature. This preserves the existing named-polygon behavior and lets Planetiler omit the attribute naturally when ele is absent.

Add a regression test covering natural=peak with ele to make sure peak POIs expose elevation.

Verification: ran PoisTest, full mvn package, spotless:check, git diff --check, and before/after Saarland PMTiles scans. The Saarland z15 scan changed from 0/489 peak features with elevation before the fix to 425/489 after the fix; the remaining peaks lack OSM ele in the source.

AI assistance: this change was prepared with help from OpenAI Codex.

* Parse POI elevation as numeric

OSM ele represents elevation in metres, so expose POI elevation as a numeric tile value instead of passing through raw tag text. This applies both to polygon-derived POIs that already carried elevation and to point POIs added by the previous change.

Add a conservative parser that accepts clean signed decimal values, including an optional trailing m suffix with or without whitespace, and emits rounded integer metres. Omit elevation when ele contains other units or free text. Update POI tests to assert integer elevation for peak and named polygon output and cover decimal, metre-suffixed, and invalid values.

AI assistance: This change was prepared with help from OpenAI Codex.

Author: candux

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

@@ -25,10 +25,15 @@
 import com.protomaps.basemap.names.OsmNames;
 import java.util.List;
 import java.util.Map;
+import java.util.regex.Pattern;
 
 @SuppressWarnings("java:S1192")
 public class Pois implements ForwardingProfile.LayerPostProcessor {
 
+  // Matches numeric metre values with an optional trailing "m" suffix, e.g. "569", "569.5", "569 m", or "569m".
+  private static final Pattern ELEVATION_PATTERN =
+    Pattern.compile("^([+-]?(?:\\d+(?:\\.\\d+)?|\\.\\d+))(?:\\s*m)?$");
+
   private Map<String, int[][]> qrankGrading = Map.of(
     "station", new int[][]{{10, 50000}, {12, 20000}, {13, 10000}},
     "aerodrome", new int[][]{{10, 50000}, {12, 20000}, {13, 5000}, {14, 2500}},
@@ -46,6 +51,25 @@ public Pois(QrankDb qrankDb) {
 
   public static final String LAYER_NAME = "pois";
 
+  static Integer parseElevation(String elevation) {
+    if (elevation == null) {
+      return null;
+    }
+
+    var matcher = ELEVATION_PATTERN.matcher(elevation.trim());
+    if (!matcher.matches()) {
+      return null;
+    }
+
+    var parsed = parseDoubleOrNull(matcher.group(1));
+    if (parsed == null) {
+      return null;
+    }
+
+    var rounded = Math.round(parsed);
+    return rounded >= Integer.MIN_VALUE && rounded <= Integer.MAX_VALUE ? (int) rounded : null;
+  }
+
   private static final Expression WITH_OPERATOR_USFS = with("operator", "United States Forest Service",
     "US Forest Service", "U.S. Forest Service", "USDA Forest Service", "United States Department of Agriculture",
     "US National Forest Service", "United State Forest Service", "U.S. National Forest Service");
@@ -501,9 +525,7 @@ public void processOsm(SourceFeature sf, FeatureCollector features) {
 
     // Assign outputFeature
     if (hasNamedPolygon) {
-      outputFeature = features.pointOnSurface(this.name())
-        //.setAttr("area_debug", wayArea) // DEBUG
-        .setAttr("elevation", sf.getString("ele"));
+      outputFeature = features.pointOnSurface(this.name());
     } else if (sf.isPoint()) {
       outputFeature = features.point(this.name());
     } else {
@@ -525,7 +547,8 @@ public void processOsm(SourceFeature sf, FeatureCollector features) {
       .setZoomRange(Math.min(minZoom, 15), 15)
       // Core OSM tags for different kinds of places
       // Special airport only tag (to indicate if it's an airport with regular commercial flights)
-      .setAttr("iata", sf.getString("iata"));
+      .setAttr("iata", sf.getString("iata"))
+      .setAttr("elevation", parseElevation(sf.getString("ele")));
 
     // Core Tilezen schema properties
     if (!kindDetail.equals("pm:undefined"))

tiles/src/test/java/com/protomaps/basemap/layers/PoisTest.java

@@ -1,6 +1,7 @@
 package com.protomaps.basemap.layers;
 
 import static com.onthegomap.planetiler.TestUtils.*;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 
 import com.onthegomap.planetiler.reader.SimpleFeature;
 import java.util.HashMap;
@@ -197,6 +198,61 @@ void zoom_14_peak() {
       )));
   }
 
+  @Test
+  void peakElevation() {
+    assertFeatures(14,
+      List.of(Map.of("kind", "peak", "min_zoom", 14, "elevation", 569)),
+      process(SimpleFeature.create(
+        newPoint(1, 1),
+        new HashMap<>(Map.of("natural", "peak", "ele", "569")),
+        "osm", null, 0
+      )));
+  }
+
+  @Test
+  void peakElevationDecimal() {
+    assertFeatures(14,
+      List.of(Map.of("kind", "peak", "min_zoom", 14, "elevation", 570)),
+      process(SimpleFeature.create(
+        newPoint(1, 1),
+        new HashMap<>(Map.of("natural", "peak", "ele", "569.5")),
+        "osm", null, 0
+      )));
+  }
+
+  @Test
+  void peakElevationMeterSuffix() {
+    assertFeatures(14,
+      List.of(Map.of("kind", "peak", "min_zoom", 14, "elevation", 569)),
+      process(SimpleFeature.create(
+        newPoint(1, 1),
+        new HashMap<>(Map.of("natural", "peak", "ele", "569 m")),
+        "osm", null, 0
+      )));
+  }
+
+  @Test
+  void peakElevationMeterSuffixWithoutWhitespace() {
+    assertFeatures(14,
+      List.of(Map.of("kind", "peak", "min_zoom", 14, "elevation", 569)),
+      process(SimpleFeature.create(
+        newPoint(1, 1),
+        new HashMap<>(Map.of("natural", "peak", "ele", "569m")),
+        "osm", null, 0
+      )));
+  }
+
+  @Test
+  void peakElevationNonMeterUnitOmitted() {
+    var features = process(SimpleFeature.create(
+      newPoint(1, 1),
+      new HashMap<>(Map.of("natural", "peak", "ele", "569 ft")),
+      "osm", null, 0
+    ));
+
+    assertFalse(toMap(features.iterator().next(), 14).containsKey("elevation"));
+  }
+
   @Test
   void zoom_14_golfCourse() {
     assertFeatures(14,
@@ -629,7 +685,7 @@ void zoom_8_forest_largeArea() {
   @Test
   void zoom_12_tallBuilding_100mHeight() {
     assertFeatures(12,
-      List.of(Map.of("kind", "office", "min_zoom", 12, "name", "Skyscraper", "elevation", "100")),
+      List.of(Map.of("kind", "office", "min_zoom", 12, "name", "Skyscraper", "elevation", 100)),
       process(SimpleFeature.create(
         AREA_12K_SQ_M,
         new HashMap<>(Map.of(