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Querying Features

Feature collections can be queried to provide sets of features, or to return a single feature.

Query features

The path /collections/{collid}/items is the basic query to return a set of features from a feature collection.

The response is a GeoJSON feature collection containing the result.

Example

http://localhost:9000/collections/ne.admin_0_countries/items

Additional query parameters can be appended to the basic query to provide control over what sets of features are returned.

These are analagous to using SQL statement clauses to control the results of a query. In fact the service implements these using exactly that technique. This provides maximum performance since it allows the Postgres SQL engine to optimize the query execution plan.

Limiting and paging results

The query parameter limit=N can be added to the query to control the maximum number of features returned in a response document. There is also a server-defined maximum which cannot be exceeded.

The query parameter offset=N specifies the offset in the actual query result at which the response feature set starts.

Used together these two parameters allow paging through large result sets.

Example

http://localhost:9000/collections/ne.admin_0_countries/items?limit=50&offset=200

Ordering results

The result set can be ordered by any property it contains. This allows performing “greatest N” or “smallest N” queries.

  • orderBy=PROP orders results by PROP in ascending order

The sort order can be specified by appending :A (ascending) or :D (descending) to the ordering property name. The default is ascending order.

  • orderBy=PROP:A orders results by PROP in ascending order
  • orderBy=PROP:D orders results by PROP in descending order

Example

http://localhost:9000/collections/ne.admin_0_countries/items?orderBy=name

Filter by bbox

The query parameter bbox=MINX,MINY,MAXX,MAXY can be used to limit the features returned to those that intersect a specified bounding box. The bounding box is specified in geographic coordinates (longitude/latitude).

Example

http://localhost:9000/collections/ne.admin_0_countries/items?bbox=10.4,43.3,26.4,47.7

Specify result properties

The query parameter properties=PROP1,PROP2,PROP3... can be used to restrict the properties which are returned in the response. This allows reducing the response size of feature collections which have a large number of properties.

Example

http://localhost:9000/collections/ne.admin_0_countries/items?properties=name,abbrev,pop_est

Query a single feature

The path /collections/{collid}/items/{fid} allows querying a single feature in a feature collection by specifying its ID.

The response is a GeoJSON feature containing the result.

Example

http://localhost:9000/collections/ne.admin_0_countries/items/23

Specify properties in result

The query parameter properties=PROP1,PROP2,PROP3... can be used to restrict the properties which are returned in the response.

Example

http://localhost:9000/collections/ne.admin_0_countries/items/23?properties=name,abbrev,pop_est