Incorporate grid rank into city rank

layers/place/README.md

@@ -11,8 +11,12 @@ We suggest you use different font styles and sizes to create a text hierarchy.
 - **name**: The OSM [`name`](http://wiki.openstreetmap.org/wiki/Key:name) value of the POI.
 - **rank**: Countries, states and the most important cities all have a `rank` to boost their importance on the map.
 The `rank` field for counries and states ranges from `1` to `6` while the `rank` field for
-cities ranges from `1` to `10`. Use the `rank` field to build a text hierarchy.
-The rank value is a combination of the Natural Earth `scalerank`, `labelrank` and `datarank` values.
+cities ranges from `1` to `10` for the most important cities and continues from `10` serially based
+on the local importance of the city (derived from population and city class).
+Use the `rank` field to build a text hierarchy.
+The rank value is a combination of the Natural Earth `scalerank`, `labelrank` and `datarank` values for countries
+and states and for cities consists out of a shifted Natural Earth `scalerank` combined with a local rank
+within a grid for cities that do not have a Natural Earth `scalerank`.
 - **class**: Distinguish between `country`, `state` and other city classes like
 `city`, `town`, `village`, `hamlet`, `suburb`, `neighbourhood` or `isolated_dwelling`.
 Use this to separately style the different places according to their importance (usually country and state different

layers/place/city.sql

@@ -7,14 +7,15 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, class c
         OR (zoom_level BETWEEN 3 AND 7 AND "rank" <= zoom_level)
       )
     UNION ALL
-    SELECT osm_id, geometry, name, name_en, place, "rank" FROM (
-        SELECT osm_id, geometry, name, name_en, place, "rank",
-			row_number() OVER (
-				PARTITION BY LabelGrid(geometry, 150 * pixel_width)
-				ORDER BY place ASC NULLS LAST,
-				population DESC NULLS LAST,
-				length(name) DESC
-			) AS gridrank
+    SELECT osm_id, geometry, name, name_en, place, COALESCE("rank", gridrank + 10) FROM (
+      SELECT osm_id, geometry, name, name_en, place, "rank",
+      row_number() OVER (
+        PARTITION BY LabelGrid(geometry, 150 * pixel_width)
+        ORDER BY "rank" ASC NULLS LAST,
+        place ASC NULLS LAST,
+        population DESC NULLS LAST,
+        length(name) ASC
+      )::int AS gridrank
         FROM osm_city_point
         WHERE geometry && bbox
           AND ((zoom_level BETWEEN 8 AND 9 AND place <= 'town'::city_class)
@@ -23,7 +24,7 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, class c
             OR (zoom_level >= 14)
           )
     ) AS ranked_places
-    WHERE (zoom_level = 8 AND gridrank <= 4)
-       OR (zoom_level BETWEEN 9 AND 12 AND gridrank <= 9)
+    WHERE (zoom_level = 8 AND (gridrank <= 4 OR "rank" IS NOT NULL))
+       OR (zoom_level BETWEEN 9 AND 12 AND (gridrank <= 9 OR "rank" IS NOT NULL))
        OR (zoom_level >= 13);
 $$ LANGUAGE SQL IMMUTABLE;

layers/place/place.yaml

@@ -16,9 +16,12 @@ layer:
     rank: |
         Countries, states and the most important cities all have a `rank` to boost their importance on the map.
         The `rank` field for counries and states ranges from `1` to `6` while the `rank` field for
-        cities ranges from `1` to `10`. Use the `rank` field to build a text hierarchy.
+        cities ranges from `1` to `10` for the most important cities and continues from `10` serially based
+        on the local importance of the city (derived from population and city class).
+        Use the `rank` field to build a text hierarchy.
         The rank value is a combination of the Natural Earth `scalerank`, `labelrank` and `datarank` values for countries
-        and states and a shifted Natural Earth `scalerank` for cities.
+        and states and for cities consists out of a shifted Natural Earth `scalerank` combined with a local rank
+        within a grid for cities that do not have a Natural Earth `scalerank`.
   buffer_size: 128
   datasource:
     geometry_field: geometry