Advanced Spatial Querying & WFS

Master the Web Feature Service (WFS) to perform complex spatial operations, filter geometries, and optimize data retrieval for high-performance applications.

⚠️

High-Volume Warning When querying large datasets via WFS 2.0, always specify a maxFeatures limit. Unbounded requests can cause server memory exhaustion.

1. CQL Filter Syntax

Common Query Language (CQL) allows you to filter features on the server-side before transmission. This reduces bandwidth significantly compared to downloading raw data and filtering client-side.

cURL

GET /geoserver/wfs?service=WFS&
version=2.0.0&
request=GetFeature&
typename=topp:states&
outputFormat=application/json&
cql_filter="POP_RANK > 3 AND INTERSECTS(the_geom, POLYGON((-120 40, -120 60, -80 60, -80 40, -120 40)))"

Key Spatial Operators:

INTERSECTS(geometry, geometry): Select features overlapping a boundary.
WITHIN(geometry, geometry): Select features completely inside a boundary.
DWITHIN(geometry, geometry, distance, units): Proximity search (e.g., within 5km).
CONTAINS(geometry, geometry): Select features containing a point/polygon.

2. Query Optimization Tabs

Using BBOX for Viewport Clipping

The most efficient way to load data for a map viewport is using the BBOX parameter. GeoServer will intersect your features with the bounding box coordinates.

URL Param

BBOX=minX,minY,maxX,maxY,CRS

Example:
BBOX=-180,-90,180,90,EPSG:4326

Note: Always specify the CRS at the end of the BBOX string to avoid coordinate system mismatches.

Sorting Results

Use SORTBY to order features. This is crucial for styling overlays (e.g., rendering smaller points on top of larger ones).

XML Filter

<SortBy>
  <SortProperty>
    <PropertyName>POP_RANK</PropertyName>
    <SortOrder>DESCEND</SortOrder>
  </SortProperty>
</SortBy>

Geometry Transformation

Use PROPERTYNAME with the transform function to modify geometries on the fly (e.g., buffering a feature before sending it).

SQL-92

propertyname="transform(the_geom, 100) AS buffered_geom, NAME"

This creates a temporary 100-unit buffer around the_geom without altering the source database.

3. Advanced Response Handling

When working with GeoJSON output, you can use FEATUREID to map specific IDs or use INFO format to get raw binary data for high-performance rendering engines like WebGL.

JSON Response Sample

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "id": "states.10",
      "geometry": {
        "type": "Polygon",
        "coordinates": [...]
      },
      "properties": {
        "STATE_FIPS": "06",
        "STATE_NAME": "California",
        "POP_RANK": 1
      }
    }
  ]
}

Next Steps

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