public int minZoomWithData() {
      return IntStream.range(0, byTile.size())
        .filter(i -> byTile.get(i).numTiles() > 0)
        .min()
        .orElse(PlanetilerConfig.MAX_MAXZOOM);
    }
Returns the minimum zoom a tile appears at in the tileset.
planetiler-core/src/main/java/com/onthegomap/planetiler/util/TilesetSummaryStatistics.java