public double getPixelSizeAtZoom(int zoom) {
    try {
      return source.size() * (256 << zoom);
    } catch (GeometryException e) {
      e.log(stats, "source_feature_pixel_size_at_zoom_failure",
        "Error getting source feature pixel size at zoom from geometry " + source);
      return 0;
    }
  }
Returns the actual pixel size of the source feature at {@code zoom} (length if line, sqrt(area) if polygon).
planetiler-core/src/main/java/com/onthegomap/planetiler/FeatureCollector.java