ElasticGraph Query API: Geographic Grouping

$ curl -s https://block.github.io/elasticgraph/dc.yml | docker compose -f - up --pull always

GeoLocation fields can be grouped into Web Mercator map tiles using asGeoTile:

query VenueCountsByGeoTile {
  venueAggregations {
    nodes {
      count
      groupedBy {
        location {
          asGeoTile(zoomLevel: 8) {
            zoomLevel
            x
            y
            mapCenterPoint {
              latitude
              longitude
            }
            bounds {
              north
              south
              east
              west
            }
            corners {
              northwest { latitude longitude }
              northeast { latitude longitude }
              southwest { latitude longitude }
              southeast { latitude longitude }
            }
          }
        }
      }
    }
  }
}

The zoomLevel argument (0 to 29, default 7) controls the tile size. At zoom level z, the map is divided into a 2^z by 2^z grid, so each increase in zoom level gives tiles one quarter the size.

Each tile provides:

• zoomLevel, x, and y: the tile’s position in the grid. x increases west to east and y increases north to south, both ranging from 0 up through 2^z - 1.
• mapCenterPoint: The center of the tile as drawn on a Web Mercator map, not the average record location or the midpoint of the tile’s latitude bounds. These differ noticeably only at low zoom levels: for tile 1/0/0, the map center point is at about 66.51° latitude, but the bounds midpoint is at about 42.53°.
• bounds: the north and south latitudes and the east and west longitudes of the tile.
• corners: the northwest, northeast, southwest, and southeast points of the tile, which are useful to draw the tile as a polygon.

Some things to keep in mind:

• Tiles are square on the map, but their size on the ground changes with latitude.
• The map stops at approximately ±85.0511° latitude. Locations nearer the poles go into the top or bottom row of tiles, outside of that tile’s bounds.
• A location on the edge between two tiles goes into the tile to the east or south.