s2-geometry

s2-geometry (JavaScript/ES5.1)
======================

| Sponsored by ppl

A pure JavaScript/ES5.1 port of Google/Niantic's S2 Geometry library (as used by Ingress, Pokemon GO)

Currently contains basic support for S2Cell

Where is this being used?
---------------------

* pokemap-webapp
* node-pokemap
* Pokemon-GO-node-api

Simple Examples
---------------

``javascript
'use strict';

var S2 = require('s2-geometry').S2;

var lat = 40.2574448;
var lng = -111.7089464;
var level = 15;

//
// Convert from Lat / Lng
//
var key = S2.latLngToKey(lat, lng, level);
// '4/032212303102210'

//
// Convert between Hilbert Curve Quadtree Key and S2 Cell Id
//
var id = S2.keyToId(key);
// '9749618446378729472'

var key = S2.idToKey(id);
// '9749618446378729472'


//
// Convert between Quadkey and Id
//
var latlng = S2.keyToLatLng(key);
var latlng = S2.idToLatLng(id);

//
// Neighbors
//
var neighbors = S2.latLngToNeighborKeys(lat, lng, level);
// [ keyLeft, keyDown, keyRight, keyUp ]

//
// Previous, Next, and Step
//
var nextKey = S2.nextKey(key);
var prevKey = S2.prevKey(key);

var backTenKeys = S2.stepKey(key, -10);
`

Previous and Next
-----------------

You can get the previous and next S2CellId from any given Key:

1. Convert from Lat/Lng to Key (Face and Hilbert Curve Quadtree)
2. Get the Previous or Next Key
3. Convert the Key to an Id (uint64 string)

`javascript
var key = S2.latLngToKey(40.2574448, -111.7089464, 15); // '4/032212303102210'
var id = S2.keyToId(key); // '9749618446378729472'

var nextKey = S2.nextKey(key);
var nextId = S2.keyToId(nextKey);

var prevKey = S2.prevKey(key);
var prevId = S2.keyToId(prevKey);

var backTenKeys = S2.stepKey(key, -10);

// See it
console.log(prevKey); // '4/032212303102203'
console.log(key); // '4/032212303102210'
console.log(nextKey); // '4/032212303102211'
console.log(nextId);
`

convert Cell Id to Hilbert Curve Quad Tree
------------------

Convert from base 10 (decimal) S2 Cell Id to base 4 quadkey (aka hilbert curve quadtree id)

Example '4/032212303102210' becomes '9749618446378729472'

`javascript
'use strict';

var quadkey = '4/032212303102210'
var parts = quadkey.split('/');
var face = parts[0]; // 4
var position = parts[1]; // '032212303102210';
var level = '032212303102210'.length; // 15

var cellId = S2.facePosLevelToId(face, position, level);

console.log(cellId);
`

Convert from hilbert quadtree id to s2 cell id:

Example '9749618446378729472' becomes '4/032212303102210'

`javascript
'use strict';

var cellId = '9749618446378729472';

var hilbertQuadkey = S2.idToKey(cellId);

console.log(hilbertQuadkey);
`

Convert Key and Id to LatLng
---------------------

`javascript
var latlng = S2.keyToLatLng('4/032212303102210');

var latlng = S2.idToLatLng('9749618446378729472');
``