Geodist

A fast and simple geographical distance calculator. This module calculates
"as the crow flies" distance between two points using the haversine formula.

Installation

Install using npm:

$ npm install geodist

Example

To get the mileage between two points, pass in the coordinates in decimal
format.

var geodist = require('geodist')

var dist = geodist({lat: 41.85, lon: -87.65}, {lat: 33.7489, lon: -84.3881})
console.log(dist)
// => 587

Usage

#### geodist(start, end, [options])

The following options are supported:

* unit - Return results in the unit of measurement. Defaults to miles, see below for available types.
* format - Return results as a string with the measurement type. Defaults to false.
* exact - Return exact results as a floating point. Defaults to false.
* limit - Specify a maximum distance here and true will be returned if the distance is less, or false if it is exceeded.

The following types are accepted in the unit option:

* miles or mi
* yards
* feet
* kilometers or km
* meters

Examples:

var geodist = require('geodist')

var tokyo = {lat: 35.6833, lon: 139.7667}
var osaka = {lat: 34.6603, lon: 135.5232}

geodist(tokyo, osaka) // => 249

geodist(tokyo, osaka, {exact: true, unit: 'km'}) // => 402.09212137829695

geodist(tokyo, osaka, {format: true, unit: 'feet'}) // => 1319614 feet

geodist(tokyo, osaka, {limit: 200}) // => false

geodist(tokyo, osaka, {limit: 250}) // => true

Coordinate formats

Coordinates are always in decimal format and can be passed in one of three
ways:

##### An object hash with explicit lat/lon keys:

var dist = geodist({lat: 41.85, lon: -87.65}, {lat: 33.7489, lon: -84.3881})

##### An object hash with arbitrary keys (in lat/lon order):

var dist = geodist({x: 41.85, y: -87.65}, {latitude: 33.7489, longitude: -84.3881})

##### An array (in lat/lon order):

var dist = geodist([41.85, -87.65], [33.7489, -84.3881])

Running the tests

To run the test suite, invoke the following commands in the repository:

$ npm install
$ npm test

Acknowledgements

Thanks to Movable Type for supplying
the initial JavaScript implementation of the haversine formula that this is based on.