Spatial Table Join

Provide two GeoJSON FeatureCollections and calculate which polygon contains each point or has it on a boundary. Choose the first matching zone or keep all overlaps, and decide whether boundary points count. The output retains original point properties, adds zone attributes with a zone_ prefix, and reports points with no zone and zones with no point. This tool supports 2D RFC 7946 WGS 84 longitude–latitude Point and Polygon features only. It does not calculate roads, distance or coordinate transformations.

Two GeoJSON inputs

Each input is a UTF-8 FeatureCollection up to 120 KB. Points on the left must be Point; zones on the right must be Polygon. An empty zone list is allowed.

Point FeatureCollection

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "id": "p-center",
      "properties": {
        "name": "Both zones",
        "visits": 4
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          3.5,
          2
        ]
      }
    },
    {
      "type": "Feature",
      "id": "p-hole",
      "properties": {
        "name": "Inside A hole"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          1.5,
          1.5
        ]
      }
    },
    {
      "type": "Feature",
      "id": "p-edge",
      "properties": {
        "name": "A east edge"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          4,
          2
        ]
      }
    },
    {
      "type": "Feature",
      "id": "p-outside",
      "properties": {
        "name": "Outside"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          8,
          2
        ]
      }
    }
  ]
}

Polygon zone FeatureCollection

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "id": "zone-a",
      "properties": {
        "name": "Zone A",
        "score": 7
      },
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              0,
              0
            ],
            [
              4,
              0
            ],
            [
              4,
              4
            ],
            [
              0,
              4
            ],
            [
              0,
              0
            ]
          ],
          [
            [
              1,
              1
            ],
            [
              1,
              2
            ],
            [
              2,
              2
            ],
            [
              2,
              1
            ],
            [
              1,
              1
            ]
          ]
        ]
      }
    },
    {
      "type": "Feature",
      "id": "zone-b",
      "properties": {
        "name": "Zone B",
        "score": 9
      },
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              3,
              0
            ],
            [
              5,
              0
            ],
            [
              5,
              4
            ],
            [
              3,
              4
            ],
            [
              3,
              0
            ]
          ]
        ]
      }
    }
  ]
}

Boundary policyOverlapping zones

Points stay in a left join. Zone attributes get a zone_ prefix, and any name collision stops the operation.

An example with two overlapping zones and four points is ready.

Comments & questions

Key features

Distinguish polygon interior, exterior boundary, hole boundary and hole interior
Keep all overlapping zone matches or only the first in input order
Join original point properties with lossless zone_-prefixed zone properties
Reject name collisions, malformed rings, antimeridian crossings and legacy CRS explicitly
Export joined GeoJSON/CSV and unmatched point/zone CSV
Show green matched and red unmatched points on a local SVG coordinate sketch

How to use

Paste a Point FeatureCollection and a Polygon FeatureCollection, or open each local file.
Choose whether boundaries count and whether to keep all overlapping zones or the first one.
Run the spatial join and inspect matched pairs, unmatched points and unmatched zones.
Download joined GeoJSON/CSV, unmatched CSV or the SVG sketch.

Use cases

Attach an area label to collected field points
Compare all overlaps with a first-zone priority policy
Audit omissions caused by polygon holes or boundary rules

Frequently asked questions

Which GeoJSON geometries are supported?

The point input accepts only 2D Point features, and the zone input only 2D Polygon features in FeatureCollections. MultiPoint, MultiPolygon, LineString, GeometryCollection and legacy CRS cause a clear error; none are silently skipped.

What if zones overlap?

All mode duplicates the point feature once per match. First mode uses the first matching zone in the zone input. Unmatched points remain as one result feature with spatial_join=null in either mode.

How are boundaries and holes treated?

A point on the outer ring or a hole ring is a boundary match only when inclusion is selected. A point inside a hole is never matched. The test uses planar longitude–latitude ring arithmetic.

Will an existing property be overwritten?

No. Point properties are retained, zone properties receive a zone_ prefix, and spatial_join metadata is added. If an original point property already has a resulting name, the join stops with a collision error.

Does it transform other coordinate systems?

No. Both inputs are interpreted as RFC 7946 WGS 84 longitude–latitude. A legacy crs member is rejected. Transform other CRS data explicitly first.

Are the coordinates sent to a server?

No. Files and results stay in current browser memory, and only user-triggered downloads write local files.

Privacy

Input GeoJSON is parsed and joined in the current browser. No map tiles or external analysis APIs receive the coordinates, and the tool does not store input files on a server.

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