geojson-tools.js
GeoJSON-Tools is a JavaScript module for working with location data, primarily using the GeoJSON specification.
We created GeoJSON-Tools from rwt.to in order to use it on related projects that rely on GeoJSON (primarily for MongoDB's GeoJSON support).
You are welcome to use it, submit bug reports, add feature and pull requests!
Installation
Install node.js, then: ```sh $ npm install geojson-tools ```Documentation
Calculations
Conversions
Validations
Calculations
getDistance(array, decimals optional)
Calculates the distance of an array of locations. Arguments- array - an array of locations, in the format
[lat, lng].
- decimals - the decimal points to round answer to, defaults to 3 decimal points.
[20, 30],complexify(linestring, distance)
ConvertLineString or array of coordinates to a 'complex' line with specified maximum distance between each set of points.
Arguments
- linestring - a valid GeoJSON
LineString, or an array of locations, in the format[lat, lng].
- distance - the maximum distance between each two locations, in meters. Minimum distance must be 10 meters.
[20, 30],20,3020.01374457881841,29.9862554211815920.02749358953798,29.9725064104620220.04124228409795,29.9587577159020520.054991756377518,29.94500824362248220.068742346786582,29.93125765321341820.082493595207826,29.91750640479217420.09624419012715,29.9037558098728520.109998454446686,29.89000154555331420.1237529737179,29.876247026282120.13750307275061,29.8624969272493920.151256033129513,29.84874396687048720.165010879444292,29.83498912055570820.17876504224938,29.8212349577506220.192520769690717,29.80747923030928320.206277898630216,29.79372210136978420.22003390658687,29.7799660934131320.233790231590877,29.76620976840912320.247544863923423,29.75245513607657720.261305062529242,29.73869493747075820.275060711787024,29.72493928821297620.288822447172574,29.71117755282742620.3025819531983,29.697418046801720.3163428239271,29.683657176072920.330106243909288,29.66989375609071220.34386828218919,29.6561317178108120.357630509669633,29.64236949033036720.37139577415928,29.6286042258407220.385162033041937,29.61483796695806320.398927945160654,29.60107205483934620.412692053486403,29.58730794651359720.426458446138625,29.57354155386137520.4402208587639,29.559779141236120.45398897904669,29.5460110209533120.467757803444808,29.53224219655519220.481524285475142,29.51847571452485820.49529252216346,29.5047074778365420.5,29.5Conversions
toGeoJSON(array, type)
Takes an input of an array and aGeoJSON type, and returns that GeoJSON object.
Arguments
- array - an array of locations, in the format
[lat, lng].
- type - the type of
GeoJSONobject to return (note that this is not case-sensitive).
LineString and Polygon.
Note: Other GeoJSON types will be supported in future versions.
Examples
To convert to GeoJSON::Point
Note that the array can be shallow or nested, but has to contain only one set of coordinates.
```js
var array = 20, 30;
toGeoJSON(array); // or toGeoJSON(array, 'point');
// {"type":"Point","coordinates":30,20}
```
To convert to GeoJSON::LineString
```js
var array =
20, 30,
20.5, 29.5
;
toGeoJSON(array, 'linestring');
// {"type":"LineString","coordinates":30,20,29.5,20.5}
```
To convert to GeoJSON::Polygon
The minimum number of coordinates should be 4, and there is no need to add the last coordinate in the array.
Polygons with holes are supported, however we currently do not test the validity of the holes.
```js
var array =
20, 30,
20.5, 29.5,
21, 30.5
;
toGeoJSON(array, 'polygon');
// {"type":"Polygon","coordinates":30,20,29.5,20.5,30.5,21,30,20}
```
toArray(geoobj)
Takes an input of aGeoJSON type, and returns coordinates in [lat, lng] format.
A single set of coordinates for a Point, or an array for other types.
Arguments
- geoobj - a valid
GeoJSONobject of the following types:Point,LineString,Polygon,MultiPoint,MultiLineStringorMultiPolygon.
Feature, FeatureCollection and GeometryCollection objects are unsupported.
The logic being that it would make it difficult to work with such deeply nested arrays, and that the primary GeoJSON objects
would be mixed.
To convert the above to arrays, rather convert the individual geometries in the feature etc.
Examples
To convert from GeoJSON::Point
Note that the array can be shallow or nested, but has to contain only one set of coordinates.
```js
var geoobj = {"type":"Point","coordinates":30,20};
toArray(geoobj);
// 20,30
```
To convert from GeoJSON::LineString
```js
var geoobj = {"type":"LineString","coordinates":30,20,29.5,20.5};
toArray(geoobj);
// 20,30,20.5,29.5
```
To convert from GeoJSON::Polygon
The minimum number of coordinates should be 3, and there is no need to add the last coordinate in the array.
```js
var geoobj = {"type":"Polygon","coordinates":30,20,29.5,20.5,30.5,21,30,20};
toArray(geoobj);
// 20,30,20.5,29.5,21,30.5
```
Validations
isGeoJSON(obj, returnError)
Takes an input of an object, and returns atrue or false. Include a Boolean to return a validation message for invalid objects.
Arguments
- obj - an object, either valid or invalid
GeoJSON.
- returnError - a
Booleanindicating whether to return a validation message if obj is invalid.
returnError is true.
Note: All GeoJSON types are supported in the isGeoJSON check. They are:
Point
MultiPoint
LineString
MultiLineString
Polygon
MultiPolygon
Feature
FeatureCollection
GeometryCollection
Caveats
- We currently do not check the order of
LinearRingsinside aPolygon
- All
coordinatessupplied are expected to be numbers, we do notparseFloats
- Though the library expects users to be using WGS84, we do not check bounds of lat and lng
GeoJSON::Point
```js
var geoobj = {"type":"Point","coordinates":30,20};
isGeoJSON(geoobj, true);
// true
```
To validate an invalid GeoJSON::LineString
```js
var geoobj = {"type":"LineString","coordinate":30,20,29.5,20.5};
// note the 'coordinate', expecting 'coordinates'
isGeoJSON(geoobj, true);
// {result: false, message: "invalid GeoJSON type supplied"}
```
