compute

This module provides operators to compute derived information from GeoJSON objects.

computeGeoJsonBoundingBox

Signature

computeGeoJsonBoundingBox (geoJson, options)

Description

Computes the bounding box of any GeoJSON object as a flat coordinate array [west, south, east, north] in 2D, or [west, south, minAlt, east, north, maxAlt] in 3D.

Accepts a plain geometry, a Feature, or a FeatureCollection. Features with a null geometry are silently ignored.

The 3D form is produced automatically when at least one position carries an altitude value. Returns null if no positions can be extracted.

Parameters

Name	Type	Required	Description
geoJson	object	yes	Any valid GeoJSON object
options.ignore3D	boolean	no	If true, altitude values are ignored and a 2D bbox is always returned. Defaults to false

Returns

Type	Description
number[] | null	A 2D bbox [west, south, east, north], a 3D bbox [west, south, minAlt, east, north, maxAlt], or null if no positions are available

Throws

Throws if geoJson is not a valid GeoJSON object.

Throws if options does not match the expected schema.

Examples

// Point
computeGeoJsonBoundingBox({
  type: 'Point',
  coordinates: [2.349, 48.864]
})
// [2.349, 48.864, 2.349, 48.864]

// LineString
computeGeoJsonBoundingBox({
  type: 'LineString',
  coordinates: [
    [-73.985, 40.748],
    [-87.623, 41.881],
    [-118.243, 34.052]
  ]
})
// [-118.243, 34.052, -73.985, 41.881]

// Polygon with hole — hole coordinates are included in the bbox
computeGeoJsonBoundingBox({
  type: 'Polygon',
  coordinates: [
    [[-10, -10], [10, -10], [10, 10], [-10, 10], [-10, -10]],
    [[-5, -5], [5, -5], [5, 5], [-5, 5], [-5, -5]]
  ]
})
// [-10, -10, 10, 10]

// 3D LineString — altitude range included automatically
computeGeoJsonBoundingBox({
  type: 'LineString',
  coordinates: [
    [6.865, 45.832, 1034],
    [7.742, 45.921, 672],
    [7.315, 45.074, 250]
  ]
})
// [6.865, 45.074, 250, 7.742, 45.832, 1034]

// Ignore altitude
computeGeoJsonBoundingBox(
  {
    type: 'LineString',
    coordinates: [
      [6.865, 45.832, 1034],
      [7.742, 45.921, 672],
      [7.315, 45.074, 250]
    ]
  },
  { ignore3D: true }
)
// [6.865, 45.074, 7.742, 45.832]

// Feature
computeGeoJsonBoundingBox({
  type: 'Feature',
  geometry: {
    type: 'Point',
    coordinates: [2.349, 48.864]
  },
  properties: { name: 'Paris' }
})
// [2.349, 48.864, 2.349, 48.864]

// Feature with null geometry
computeGeoJsonBoundingBox({
  type: 'Feature',
  geometry: null,
  properties: {}
})
// null

// FeatureCollection
computeGeoJsonBoundingBox({
  type: 'FeatureCollection',
  features: [
    {
      type: 'Feature',
      geometry: { type: 'Point', coordinates: [2.349, 48.864] },
      properties: {}
    },
    {
      type: 'Feature',
      geometry: { type: 'Point', coordinates: [28.979, 41.015] },
      properties: {}
    }
  ]
})
// [2.349, 41.015, 28.979, 48.864]

// FeatureCollection with null geometries — ignored silently
computeGeoJsonBoundingBox({
  type: 'FeatureCollection',
  features: [
    {
      type: 'Feature',
      geometry: { type: 'Point', coordinates: [2.349, 48.864] },
      properties: {}
    },
    {
      type: 'Feature',
      geometry: null,
      properties: {}
    },
    {
      type: 'Feature',
      geometry: { type: 'Point', coordinates: [12.496, 41.902] },
      properties: {}
    }
  ]
})
// [2.349, 41.902, 12.496, 48.864]

// Empty FeatureCollection
computeGeoJsonBoundingBox({
  type: 'FeatureCollection',
  features: []
})
// null

// 3D FeatureCollection
computeGeoJsonBoundingBox({
  type: 'FeatureCollection',
  features: [
    {
      type: 'Feature',
      geometry: { type: 'Point', coordinates: [0, 0, 100] },
      properties: {}
    },
    {
      type: 'Feature',
      geometry: {
        type: 'LineString',
        coordinates: [[5, 5, 500], [10, 10, 200]]
      },
      properties: {}
    }
  ]
})
// [0, 0, 100, 10, 10, 500]

// Ignore altitude on a FeatureCollection
computeGeoJsonBoundingBox(
  {
    type: 'FeatureCollection',
    features: [
      {
        type: 'Feature',
        geometry: { type: 'Point', coordinates: [0, 0, 100] },
        properties: {}
      },
      {
        type: 'Feature',
        geometry: {
          type: 'LineString',
          coordinates: [[5, 5, 500], [10, 10, 200]]
        },
        properties: {}
      }
    ]
  },
  { ignore3D: true }
)
// [0, 0, 10, 10]

computeGeoJsonConvexHull

Signature

computeGeoJsonConvexHull (geoJson)

Description

Computes the 2D convex hull of a GeoJSON object from all its positions.

Altitude values are ignored. The returned geometry depends on the number and spatial distribution of the extracted positions:

• no position → null
• one position → Point
• two positions → LineString
• three or more positions → Polygon when a convex hull can be computed
• collinear positions → LineString

If a Feature has a null geometry, null is returned.

Parameters

Name	Type	Required	Description
geoJson	object	yes	Any valid GeoJSON object

Returns

Type	Description
Point | LineString | Polygon | null	The convex hull geometry, or null if no positions are available

Throws

Throws if geoJson is not a valid GeoJSON object.

Examples

// Point
computeGeoJsonConvexHull({
  type: 'Point',
  coordinates: [2.349, 48.864]
})
// { type: 'Point', coordinates: [2.349, 48.864] }

// Two positions
computeGeoJsonConvexHull({
  type: 'MultiPoint',
  coordinates: [[2.349, 48.864], [4.835, 45.764]]
})
// {
//   type: 'LineString',
//   coordinates: [[2.349, 48.864], [4.835, 45.764]]
// }

// Polygon hull
computeGeoJsonConvexHull({
  type: 'MultiPoint',
  coordinates: [
    [0, 0],
    [10, 0],
    [10, 10],
    [0, 10],
    [5, 5]
  ]
})
// {
//   type: 'Polygon',
//   coordinates: [
//     [[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]
//   ]
// }

// Collinear positions
computeGeoJsonConvexHull({
  type: 'MultiPoint',
  coordinates: [[0, 0], [5, 5], [10, 10]]
})
// {
//   type: 'LineString',
//   coordinates: [[0, 0], [10, 10]]
// }

// Feature with null geometry
computeGeoJsonConvexHull({
  type: 'Feature',
  geometry: null,
  properties: {}
})
// null

// Altitude values are ignored
computeGeoJsonConvexHull({
  type: 'MultiPoint',
  coordinates: [
    [0, 0, 100],
    [10, 0, 200],
    [0, 10, 300]
  ]
})
// {
//   type: 'Polygon',
//   coordinates: [
//     [[0, 0], [10, 0], [0, 10], [0, 0]]
//   ]
// }