74_Indexing_geo_shapes.asciidoc

Indexing geo-shapes

Shapes are represented using GeoJSON, a simple open standard for encoding two-dimensional shapes in JSON. Each shape definition contains the type of shape—`point`, line, polygon, envelope,—and one or more arrays of longitude/latitude points.

Caution

In GeoJSON, coordinates are always written as longitude followed by latitude.

For instance, we can index a polygon representing Dam Square in Amsterdam as follows:

PUT /attractions/landmark/dam_square
{
    "name" : "Dam Square, Amsterdam",
    "location" : {
        "type" : "polygon", (1)
        "coordinates" : [[ (2)
          [ 4.89218, 52.37356 ],
          [ 4.89205, 52.37276 ],
          [ 4.89301, 52.37274 ],
          [ 4.89392, 52.37250 ],
          [ 4.89431, 52.37287 ],
          [ 4.89331, 52.37346 ],
          [ 4.89305, 52.37326 ],
          [ 4.89218, 52.37356 ]
        ]]
    }
}

1. The type parameter indicates the type of shape that the coordinates represent.

2. The list of lon/lat points that describe the polygon.

The excess of square brackets in the example may look confusing, but the GeoJSON syntax is quite simple:

1. Each lon/lat point is represented as an array:

   [lon,lat]

2. A list of points is wrapped in an array to represent a polygon:

   [[lon,lat],[lon,lat], ... ]

3. A shape of type polygon can optionally contain several polygons; the first represents the polygon proper, while any subsequent polygons represent holes in the first:

   [
     [[lon,lat],[lon,lat], ... ],  # main polygon
     [[lon,lat],[lon,lat], ... ],  # hole in main polygon
     ...
   ]

See the Geo-shape mapping documentation for more details about the supported shapes.