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GeoTile Grid Aggregation

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GeoTile Grid Aggregation

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A multi-bucket aggregation that works on geo_point fields and groups points into buckets that represent cells in a grid. The resulting grid can be sparse and only contains cells that have matching data. Each cell corresponds to a map tile as used by many online map sites. Each cell is labeled using a "{zoom}/{x}/{y}" format, where zoom is equal to the user-specified precision.

High precision keys have a larger range for x and y, and represent tiles that cover only a small area.
Low precision keys have a smaller range for x and y, and represent tiles that each cover a large area.

See Zoom level documentation on how precision (zoom) correlates to size on the ground. Precision for this aggregation can be between 0 and 29, inclusive.

The highest-precision geotile of length 29 produces cells that cover less than a 10cm by 10cm of land and so high-precision requests can be very costly in terms of RAM and result sizes. Please see the example below on how to first filter the aggregation to a smaller geographic area before requesting high-levels of detail.

The specified field must be of type geo_point (which can only be set explicitly in the mappings) and it can also hold an array of geo_point fields, in which case all points will be taken into account during aggregation.

Simple low-precision request

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PUT /museums
{
    "mappings": {
          "properties": {
              "location": {
                  "type": "geo_point"
              }
          }
    }
}

POST /museums/_bulk?refresh
{"index":{"_id":1}}
{"location": "52.374081,4.912350", "name": "NEMO Science Museum"}
{"index":{"_id":2}}
{"location": "52.369219,4.901618", "name": "Museum Het Rembrandthuis"}
{"index":{"_id":3}}
{"location": "52.371667,4.914722", "name": "Nederlands Scheepvaartmuseum"}
{"index":{"_id":4}}
{"location": "51.222900,4.405200", "name": "Letterenhuis"}
{"index":{"_id":5}}
{"location": "48.861111,2.336389", "name": "Musée du Louvre"}
{"index":{"_id":6}}
{"location": "48.860000,2.327000", "name": "Musée d'Orsay"}

POST /museums/_search?size=0
{
    "aggregations" : {
        "large-grid" : {
            "geotile_grid" : {
                "field" : "location",
                "precision" : 8
            }
        }
    }
}

Response:

{
    ...
    "aggregations": {
        "large-grid": {
            "buckets": [
                {
                  "key" : "8/131/84",
                  "doc_count" : 3
                },
                {
                  "key" : "8/129/88",
                  "doc_count" : 2
                },
                {
                  "key" : "8/131/85",
                  "doc_count" : 1
                }
            ]
        }
    }
}

High-precision requests

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When requesting detailed buckets (typically for displaying a "zoomed in" map) a filter like geo_bounding_box should be applied to narrow the subject area otherwise potentially millions of buckets will be created and returned.

POST /museums/_search?size=0
{
    "aggregations" : {
        "zoomed-in" : {
            "filter" : {
                "geo_bounding_box" : {
                    "location" : {
                        "top_left" : "52.4, 4.9",
                        "bottom_right" : "52.3, 5.0"
                    }
                }
            },
            "aggregations":{
                "zoom1":{
                    "geotile_grid" : {
                        "field": "location",
                        "precision": 22
                    }
                }
            }
        }
    }
}

{
    ...
    "aggregations" : {
        "zoomed-in" : {
            "doc_count" : 3,
            "zoom1" : {
                "buckets" : [
                    {
                      "key" : "22/2154412/1378379",
                      "doc_count" : 1
                    },
                    {
                      "key" : "22/2154385/1378332",
                      "doc_count" : 1
                    },
                    {
                      "key" : "22/2154259/1378425",
                      "doc_count" : 1
                    }
                ]
            }
        }
    }
}

Options

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field	Mandatory. The name of the field indexed with GeoPoints.
precision	Optional. The integer zoom of the key used to define cells/buckets in the results. Defaults to 7. Values outside of [0,29] will be rejected.
size	Optional. The maximum number of geohash buckets to return (defaults to 10,000). When results are trimmed, buckets are prioritised based on the volumes of documents they contain.
shard_size	Optional. To allow for more accurate counting of the top cells returned in the final result the aggregation defaults to returning `max(10,(size x number-of-shards))` buckets from each shard. If this heuristic is undesirable, the number considered from each shard can be over-ridden using this parameter.

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