README.md

@terraformer/spatial

Spatial predicates for GeoJSON.

Install

npm install @terraformer/spatial

API Reference

Terraformer

• Terraformer
  • .MercatorCRS
  • .GeographicCRS
  • .applyConverter(GeoJSON, function) ⇒ object
  • .calculateBounds(GeoJSON) ⇒ Array.<Number>
  • .calculateEnvelope(GeoJSON) ⇒ Object
  • .positionToGeographic(CoordinatePair) ⇒ Array.<Number, Number>
  • .positionToMercator(CoordinatePair) ⇒ Array.<Number, Number>
  • .toMercator(GeoJSON) ⇒ object
  • .convexHull(GeoJSON) ⇒ Array.<Coordinates>
  • .isConvex(GeoJSON) ⇒ Boolean
  • .polygonContainsPoint(GeoJSON, GeoJSON) ⇒ Boolean
  • .within(GeoJSON, GeoJSON) ⇒ Boolean
  • .contains(GeoJSON, GeoJSON) ⇒ Boolean
  • .intersects(GeoJSON, GeoJSON) ⇒ Boolean
  • .toCircle(CoordinatePair, [Radius], [Steps]) ⇒ object
  • .toGeographic(GeoJSON) ⇒ object

Terraformer.MercatorCRS

WKID 3857

Kind: static constant of Terraformer

Terraformer.GeographicCRS

WKID 4326

Kind: static constant of Terraformer

Terraformer.applyConverter(GeoJSON, function) ⇒ object

Runs the passed function against every Coordinate in the geojson object.

Kind: static method of Terraformer
Returns: object - GeoJSON - GeoJSON with altered coordinates.

import { applyConverter } from "@terraformer/spatial"

applyConverter({
  type: "Point",
  coordinates: [ 45, 60 ]
}, (coord) => [coord[0] + 1, coord[1] - 1])

>> { type: "Point", coordinates: [ 46, 59 ] }

Param	Type	Description
GeoJSON	object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.
function	function	Your function will be passed a Coordinate and will be expected to return a Coordinate.

Terraformer.calculateBounds(GeoJSON) ⇒ Array.<Number>

Calculate the bounding box of the input.

Kind: static method of Terraformer
Returns: Array.<Number> - [ xmin, ymin, xmax, ymax ].

import { calculateBounds } from "@terraformer/spatial"

calculateBounds({
  type: "Point",
  coordinates: [ 45, 60 ]
})

>> [45, 60, 45, 60]

Param	Type	Description
GeoJSON	object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.

Terraformer.calculateEnvelope(GeoJSON) ⇒ Object

Calculate the envelope surrounding the input.

Kind: static method of Terraformer
Returns: Object - Object in the form { x, y, w, h }.

import { calculateEnvelope } from "@terraformer/spatial"

calculateEnvelope({
  type: "Point",
  coordinates: [ 100, 100 ]
})

>> { x: 100, y: 100, w: 0, h: 0, }

Param	Type	Description
GeoJSON	object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.

Terraformer.positionToGeographic(CoordinatePair) ⇒ Array.<Number, Number>

Reprojects the passed Coordinate pair to WGS84 (4326) spatial reference.

Kind: static method of Terraformer
Returns: Array.<Number, Number> - CoordinatePair.

import { positionToGeographic } from "@terraformer/spatial"

positionToGeographic([ -13580978, 5621521 ]) // [ 45, 60  ]

Param	Type	Description
CoordinatePair	Array.<Number, Number>	An X,Y position.

Terraformer.positionToMercator(CoordinatePair) ⇒ Array.<Number, Number>

Reprojects the passed Coordinate pair to web mercator (3857) spatial reference.

Kind: static method of Terraformer
Returns: Array.<Number, Number> - CoordinatePair.

import { positionToGeographic } from "@terraformer/spatial"

positionToMercator([ 45, 60 ]) // [ -13580978, 5621521  ]

Param	Type	Description
CoordinatePair	Array.<Number, Number>	An X,Y position.

Terraformer.toMercator(GeoJSON) ⇒ object

Reproject WGS84 (Lat/Lng) GeoJSON to Web Mercator.

Kind: static method of Terraformer
Returns: object - GeoJSON

import { toMercator } from "@terraformer/spatial"

toMercator({
  type: "Point",
  coordinates: [ 45, 60 ]
})

>> { type: "Point", coordinates: [ -13580978, 5621521 ], crs }

Param	Type	Description
GeoJSON	object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.

Terraformer.convexHull(GeoJSON) ⇒ Array.<Coordinates>

Calculate the convex hull of GeoJSON input.

Kind: static method of Terraformer
Returns: Array.<Coordinates> - An array of GeoJSON coordinates representing the convex hull of the input GeoJSON.

import { convexHull } from "@terraformer/spatial"

convexHull({
  type: "LineString",
  coordinates: [
    [ 100, 0 ], [ -45, 122 ], [ 80, -60 ]
  ]
})

>>
{
  type: "Polygon",
  coordinates: [
    [ [ 100, 0 ], [ -45, 122 ], [ 80, -60 ], [ 100, 0 ] ]
  ]
}

Param	Type	Description
GeoJSON	object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.

Terraformer.isConvex(GeoJSON) ⇒ Boolean

Determine whether input GeoJSON has a convex shape.

Kind: static method of Terraformer
Returns: Boolean - Yes/No

import { isConvex } from "@terraformer/spatial"

isConvex({
  type: "Polygon",
  coordinates: [
    [ [ 100, 0 ], [ -45, 122 ], [ 80, -60 ], [ 100, 0 ] ]
  ]
})

>> true

Param	Type	Description
GeoJSON	Object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.

Terraformer.polygonContainsPoint(GeoJSON, GeoJSON) ⇒ Boolean

Accepts the geometry of a polygon and point and returns true if the point falls within the polygon.

Kind: static method of Terraformer
Returns: Boolean - Yes/No

import { polygonContainsPoint } from "@terraformer/spatial"

polygonContainsPoint(
  [
    [ [ 1, 2 ], [ 2, 2 ], [ 2, 1 ], [ 1, 1 ], [ 1, 2 ] ]
  ],
  [ 10, 10 ]
)

>> false

Param	Type	Description
GeoJSON	Object	GeoJSON Polygon coordinates.
GeoJSON	Object	GeoJSON Point coordinates.

Terraformer.within(GeoJSON, GeoJSON) ⇒ Boolean

Returns true if the GeoJSON passed as the first argument is completely inside the GeoJSON object passed in the second position.

Kind: static method of Terraformer
Returns: Boolean - Yes/No

import { within } from "@terraformer/spatial"

within({
  type: "Point",
  coordinates: [ 10, 10 ]
},
{
  type: "Polygon",
  coordinates: [
    [ [ 5, 5 ], [ 5, 15 ], [ 15, 15 ], [ 15, 5 ], [ 5, 5 ] ]
  ]
})

>> true

Param	Type	Description
GeoJSON	Object	GeoJSON that may be within the second input.
GeoJSON	Object	GeoJSON that may contain the first input.

Terraformer.contains(GeoJSON, GeoJSON) ⇒ Boolean

Returns true if the GeoJSON passed as the second argument is completely inside the GeoJSON object passed in the first position.

Kind: static method of Terraformer
Returns: Boolean - Yes/No

import { contains } from "@terraformer/spatial"

contains({
  type: "Polygon",
  coordinates: [
    [ [ 5, 5 ], [ 5, 15 ], [ 15, 15 ], [ 15, 5 ], [ 5, 5 ] ]
]},
{
  type: "Point",
  coordinates: [ 10, 10 ]
})

>> true

Param	Type	Description
GeoJSON	Object	GeoJSON that may contain the second input.
GeoJSON	Object	GeoJSON that may be contained by the first input.

Terraformer.intersects(GeoJSON, GeoJSON) ⇒ Boolean

Returns true if the two input GeoJSON objects intersect one another.

Kind: static method of Terraformer
Returns: Boolean - Yes/No

import { intersects } from "@terraformer/spatial"

intersects({
  type: "Point",
  coordinates: [ 10, 10 ]
},
{
  type: "Polygon",
  coordinates: [
    [ [ 5, 5 ], [ 5, 15 ], [ 15, 15 ], [ 15, 5 ], [ 5, 5 ] ]
  ]
})

>> true

Param	Type	Description
GeoJSON	Object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.
GeoJSON	Object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.

Terraformer.toCircle(CoordinatePair, [Radius], [Steps]) ⇒ object

Uses an input Coordinate pair to create a GeoJSON Feature containing a Polygon representing a circle with a discrete number of sides.

Kind: static method of Terraformer
Returns: object - GeoJSON

import { toCircle } from "@terraformer/spatial"

toCircle([ -118, 34 ], 500)

>> { type: "Feature", geometry: { type: "Polygon"}, coordinates: [...] }

Param	Type	Default	Description
CoordinatePair	Array.<Number, Number>		A GeoJSON Coordinate in [x,y] format.
[Radius]	Number	250	The radius of the circle (in meters).
[Steps]	Number	64	The number of sides the output polygon will contain.

Terraformer.toGeographic(GeoJSON) ⇒ object

Reproject Web Mercator GeoJSON to WGS84 (Lat/Long).

Kind: static method of Terraformer
Returns: object - GeoJSON

import { toGeographic } from "@terraformer/spatial"

toGeographic({
  type: "Point",
  coordinates: [ -13580978, 5621521 ]
})

>> { type: "Point", coordinates: [ 45, 60 ] }

Param	Type	Description
GeoJSON	object	The input GeoJSON Geometry, Feature, GeometryCollection or FeatureCollection.

---

Usage

Browser (from CDN)

This package is distributed as a UMD module and can also be used in AMD based systems or as a global under the Terraformer namespace.

<script src="https://unpkg.com/@terraformer/spatial"></script>

const input = {
  'type': 'Polygon',
  'coordinates': [
    [ [41.83, 71.01], [56.95, 33.75], [21.79, 36.56], [41.83, 71.01] ]
  ]
};

Terraformer.isConvex(input.coordinates[0]); // true

Node.js

const Terraformer = require('@terraformer/spatial');

Terraformer.isConvex(/* ... */);

ES module in the browser

<script type='module'>
  import { isConvex } from 'https://unpkg.com/@terraformer/spatial?module';

  // look ma, no build step!
  isConvex(/* ... */);
</script>

FAQ

What's the difference between this project and Turf.js?

Both libraries work with GeoJSON and share many similar functions. Turf.js relies on JSTS, and some folks have found it to be slower. In the past Turf.js did not include predicates like 'within', 'contains' and 'intersects', but that no longer appears to be the case.

Contributing

LICENSE