Circle Processoredit

Converts circle definitions of shapes to regular polygons which approximate them.

Table 34. Circle Processor Options

NameRequiredDefaultDescription

field

yes

-

The string-valued field to trim whitespace from

target_field

no

field

The field to assign the polygon shape to, by default field is updated in-place

ignore_missing

no

false

If true and field does not exist, the processor quietly exits without modifying the document

error_distance

yes

-

The difference between the resulting inscribed distance from center to side and the circle’s radius (measured in meters for geo_shape, unit-less for shape)

shape_type

yes

-

which field mapping type is to be used when processing the circle: geo_shape or shape

if

no

-

Conditionally execute this processor.

on_failure

no

-

Handle failures for this processor. See Handling Failures in Pipelines.

ignore_failure

no

false

Ignore failures for this processor. See Handling Failures in Pipelines.

tag

no

-

An identifier for this processor. Useful for debugging and metrics.

error distance

PUT circles
{
  "mappings": {
    "properties": {
      "circle": {
        "type": "geo_shape"
      }
    }
  }
}

PUT _ingest/pipeline/polygonize_circles
{
    "description": "translate circle to polygon",
    "processors": [
      {
        "circle": {
          "field": "circle",
          "error_distance": 28.0,
          "shape_type": "geo_shape"
        }
      }
    ]
}

Using the above pipeline, we can attempt to index a document into the circles index. The circle can be represented as either a WKT circle or a GeoJSON circle. The resulting polygon will be represented and indexed using the same format as the input circle. WKT will be translated to a WKT polygon, and GeoJSON circles will be translated to GeoJSON polygons.

Example: Circle defined in Well Known Textedit

In this example a circle defined in WKT format is indexed

PUT circles/_doc/1?pipeline=polygonize_circles
{
  "circle": "CIRCLE (30 10 40)"
}

GET circles/_doc/1

The response from the above index request:

{
  "found": true,
  "_index": "circles",
  "_type": "_doc",
  "_id": "1",
  "_version": 1,
  "_seq_no": 22,
  "_primary_term": 1,
  "_source": {
    "circle": "polygon ((30.000365257263184 10.0, 30.000111397193788 10.00034284530941, 29.999706043744222 10.000213571721195, 29.999706043744222 9.999786428278805, 30.000111397193788 9.99965715469059, 30.000365257263184 10.0))"
  }
}

Example: Circle defined in GeoJSONedit

In this example a circle defined in GeoJSON format is indexed

PUT circles/_doc/2?pipeline=polygonize_circles
{
  "circle": {
    "type": "circle",
    "radius": "40m",
    "coordinates": [30, 10]
  }
}

GET circles/_doc/2

The response from the above index request:

{
  "found": true,
  "_index": "circles",
  "_type": "_doc",
  "_id": "2",
  "_version": 1,
  "_seq_no": 22,
  "_primary_term": 1,
  "_source": {
    "circle": {
      "coordinates": [
        [
          [30.000365257263184, 10.0],
          [30.000111397193788, 10.00034284530941],
          [29.999706043744222, 10.000213571721195],
          [29.999706043744222, 9.999786428278805],
          [30.000111397193788, 9.99965715469059],
          [30.000365257263184, 10.0]
        ]
      ],
      "type": "polygon"
    }
  }
}

Notes on Accuracyedit

Accuracy of the polygon that represents the circle is defined as error_distance. The smaller this difference is, the closer to a perfect circle the polygon is.

Below is a table that aims to help capture how the radius of the circle affects the resulting number of sides of the polygon given different inputs.

The minimum number of sides is 4 and the maximum is 1000.

Table 35. Circle Processor Accuracy

error_distanceradius in metersnumber of sides of polygon

1.00

1.0

4

1.00

10.0

14

1.00

100.0

45

1.00

1000.0

141

1.00

10000.0

445

1.00

100000.0

1000