# @turf/great-circle

# greatCircle

Calculate great circles routes as [LineString](http://geojson.org/geojson-spec.html#linestring)

**Parameters**

-   `start` **([Geometry](http://geojson.org/geojson-spec.html#geometry) \| [Feature](http://geojson.org/geojson-spec.html#feature-objects)<[Point](http://geojson.org/geojson-spec.html#point)> | [Array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)<[number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)>)** source point feature
-   `end` **([Geometry](http://geojson.org/geojson-spec.html#geometry) \| [Feature](http://geojson.org/geojson-spec.html#feature-objects)<[Point](http://geojson.org/geojson-spec.html#point)> | [Array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)<[number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)>)** destination point feature
-   `properties` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** line feature properties (optional, default `{}`)
-   `npoints` **\[[number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** number of points (optional, default `100`)
-   `offset` **\[[number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** offset controls the likelyhood that lines will
    be split which cross the dateline. The higher the number the more likely. (optional, default `10`)

**Examples**

```javascript
var start = turf.point([-122, 48]);
var end = turf.point([-77, 39]);

var greatCircle = turf.greatCircle(start, end, {'name': 'Seattle to DC'});

//addToMap
var addToMap = [start, end, greatCircle]
```

Returns **[Feature](http://geojson.org/geojson-spec.html#feature-objects)<[LineString](http://geojson.org/geojson-spec.html#linestring)>** great circle line feature

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---

This module is part of the [Turfjs project](http://turfjs.org/), an open source
module collection dedicated to geographic algorithms. It is maintained in the
[Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create
PRs and issues.

### Installation

Install this module individually:

```sh
$ npm install @turf/great-circle
```

Or install the Turf module that includes it as a function:

```sh
$ npm install @turf/turf
```