geojson

What is geojson?

The geojson npm package provides utilities for working with GeoJSON data, which is a format for encoding a variety of geographic data structures. It allows you to create, manipulate, and validate GeoJSON objects easily.

What are geojson's main functionalities?

Creating GeoJSON Objects

This feature allows you to create GeoJSON objects from an array of data points. The example demonstrates how to convert an array of locations with latitude and longitude into a GeoJSON object.

const geojson = require('geojson');
const data = [
  { name: 'Location 1', lat: 40.7128, lng: -74.0060 },
  { name: 'Location 2', lat: 34.0522, lng: -118.2437 }
];
const geojsonData = geojson.parse(data, { Point: ['lat', 'lng'] });
console.log(JSON.stringify(geojsonData, null, 2));

Validating GeoJSON Objects

This feature allows you to validate GeoJSON objects to ensure they conform to the GeoJSON specification. The example shows how to validate a GeoJSON object representing a point feature.

const geojson = require('geojson');
const geojsonData = {
  type: 'FeatureCollection',
  features: [
    {
      type: 'Feature',
      geometry: {
        type: 'Point',
        coordinates: [-74.0060, 40.7128]
      },
      properties: {
        name: 'Location 1'
      }
    }
  ]
};
const isValid = geojson.isValid(geojsonData);
console.log(isValid);

Converting GeoJSON to Other Formats

This feature allows you to convert GeoJSON objects to other formats such as KML. The example demonstrates how to convert a GeoJSON object to KML format.

const geojson = require('geojson');
const geojsonData = {
  type: 'FeatureCollection',
  features: [
    {
      type: 'Feature',
      geometry: {
        type: 'Point',
        coordinates: [-74.0060, 40.7128]
      },
      properties: {
        name: 'Location 1'
      }
    }
  ]
};
const kml = geojson.toKML(geojsonData);
console.log(kml);

Other packages similar to geojson

terraformer

Terraformer is a JavaScript library for working with GeoJSON, including parsing, converting, and manipulating GeoJSON data. It offers more advanced spatial operations compared to geojson, such as buffering and union operations.

geojson-utils

GeoJSON Utils is a utility library for working with GeoJSON data. It provides functions for calculating distances, bounding boxes, and other spatial operations. It is more focused on spatial calculations compared to geojson.

turf

Turf is a powerful geospatial analysis library for JavaScript. It provides a wide range of spatial operations, including measurements, transformations, and data classification. Turf is more comprehensive and feature-rich compared to geojson.

README

geojson.js

Convert an array of objects with geometry to a GeoJSON feature collection.

Installation

For node, use npm: npm install geojson

In the browser, include geojson.js. For example: <script type="text/javascript" src="js/geojson.js"></script>

Getting Started

In node, var GeoJSON = require('geojson');

In the browser, the library is available at GeoJSON.

Example Usage

The library has one method, parse, which takes an array of objects with geometry data as the first parameter, and an object consisting of settings for the second parameter.

Take the example data below:

var data = [
  {
    name: 'Location A',
    category: 'Store',
    street: 'Market',
    lat: 39.984,
    lng: -75.343
  },
  {
    name: 'Location B',
    category: 'House',
    street: 'Broad',
    lat: 39.284,
    lng: -75.833
  },
  {
    name: 'Location C',
    category: 'Office',
    street: 'South'
    lat: 39.123,
    lng: -74.534
  }
];

Convert it to GeoJSON:

GeoJSON.parse(data, {Point: ['lat', 'lng']});

  { "type": "FeatureCollection",
    "features": [
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [-75.343, 39.984]},
        "properties": { 
          "name": "Location A",
          "category": "Store"
        }
      },
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [-75.833, 39.284]},
        "properties": { 
          "name": "Location B",
          "category": "House"
        }
      },
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [ -75.534, 39.123]},
        "properties": { 
          "name": "Location C",
          "category": "Office"
        }
      }
    ]
  }

Convert the example data to GeoJSON, and only include the name attribute in properties for each feature.

GeoJSON.parse(data, {Point: ['lat', 'lng'], include: ['name']});

  { "type": "FeatureCollection",
    "features": [
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [-75.343, 39.984]},
        "properties": { 
          "name": "Location A"
        }
      },
      ...
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [ -75.534, 39.123]},
        "properties": { 
          "name": "Location C"
        }
      }
    ]
  }

The parse method can handle data with different geometry types. Consider the following sample data:

var data2 = [
  { 
    x: 0.5,
    y: 102.0,
    prop0: 'value0'
  },
  {
    line: [[102.0, 0.0], [103.0, 1.0], [104.0, 0.0], [105.0, 1.0]],
    prop0: 'value0',
    prop1: 0.0
  },
  {
    polygon: [
      [ [100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ]
    ],
    prop0: 'value0',
    prop1: {"this": "that"}
  }
];

For each geometry type, specify which attribute contains the geometric data

GeoJSON.parse(data2, {'Point': ['x', 'y'], 'LineString': 'line', 'Polygon': 'polygon'});

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [102,0.5]
      },
      "properties": {
        "prop0": "value0"
      }
    },
    {
      "type": "Feature",
      "geometry": {
        "type": "LineString",
        "coordinates": [[102, 0], [103, 1], [104, 0],[105, 1]]
      },
      "properties": {
        "prop0": "value0",
        "prop1": 0
      }
    },
    {
      "type": "Feature",
      "geometry": {
        "type": "Polygon",
        "coordinates": [[[100, 0], [101, 0], [101, 1], [100, 1], [100, 0]]]
      },
      "properties": {
        "prop0": "value0",
        "prop1": {
            "this": "that"
          }
      }
    }
  ]
}

You can also specify default settings if you will be parsing mutliple datasets with similiar attributes.

var data1 = [{
  name: 'Location A',
  street: 'Market',
  x: 34,
  y: -75
}];

var data2 = [{
  name: 'Location B',
  date: '11/23/2012',
  x: 54,
  y: -98
}];

GeoJSON.defaults = {Point: ['x', 'y'], include: ['name']};

GeoJSON.parse(data1);

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [-75, 34]
      },
      "properties": {
        "name": "Location A"
      }
    }
  ]
}

GeoJSON.parse(data2);

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [-98, 54]
      },
      "properties": {
        "name": "Location B"
      }
    }
  ]
}

Parameters

Depending on which makes more sense for the data that is being parsed, either specify an array of attributes to include or exclude in properties for each feature. If neither include nor exclude is set, all the attributes (besides the attributes containing the geometry data) will be added to feature properties.

• include - Array of attributes to include in properties for each feature. All other fields will be ignored.
• exclude - Array of attributes that shouldn't be included in feature properties. All other attributes will be added (besides geometry attributes)

The geometry parameters specify which attribute(s) contain(s) the geographic/geometric data. A geometry parameter must be specified for each type of geometry object that is present in the data that is being parsed. For example, if the data contains both points and polygons, specify both the Point and Polygon parameters. Note that geometry parameters must be in proper case. See the GeoJSON spec for details on each geometry type. The structure of the geometry parameter is:

ParameterName: 'attributeName'

Except for Point, which can be specified with a field name or an array of field names, i.e:

data = [{
  name: 'location',
  x: 34,
  y: 85
}];

GeoJSON.parse(data, {Point: ['lat', 'lng']});

or

data = [{
  name: 'location',
  coords: [85, 34]
}];

GeoJSON.parse(data, {Point: 'coords'});

The valid geometry types are

• Point
• MultiPoint
• LineString
• MultiLineString
• Polygon
• MultiPolygon

geojson.js also supports the optional GeoJSON properties bbox and crs.

• crs - A string identifying a coordinate reference system. Only named CRSs are supported at the moment. More information
• bbox - A bounding box for the feature collection. An array with the following format: [y1, x1, y2, x2]. More information

Tests

For node, npm test.

For the browser, visit test/test.html.