first working version

README.md

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+# Mapbox Elevation
+
+Quickly get the elevation of any point in the world from Mapbox's terrian-rgb datasource.
+
+This module requires a Mapbox account to use. [Get a free one here](https://www.mapbox.com/signup/).
+
+The result is in meters.
+
+For details on how this works, please see [this blog post](https://www.mapbox.com/blog/terrain-rgb/).
+
+## Usage
+
+`npm install mapbox-elevation`
+
+```js
+var MapboxElevation = require('mapbox-elevation');
+var getElevation('YOUR-MAPBOX-TOKEN');
+
+getElevation([86.925313, 27.988730], function(err, elevation) {
+  console.log('elevation at the summit of mt everest', elevation);
+});
+```

index.js

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+var tilebelt = require('@mapbox/tilebelt');
+var pkg = require('./package.json');
+var getPixels = require('get-pixels');
+
+module.exports = function(tk) {
+  return function(p, cb) {
+    var tf = tilebelt.pointToTileFraction(p[0], p[1], 20);
+    var tile = tf.map(Math.floor);
+    var domain = 'https://api.mapbox.com/v4/';
+    var source = `mapbox.terrain-rgb/${tile[2]}/${tile[0]}/${tile[1]}.pngraw`;
+    var url = `${domain}${source}?access_token=${tk}`;
+    getPixels(url, function(err, pixels) {
+      if (err) return cb(err);
+      var xp = tf[0] - tile[0];
+      var yp = tf[1] - tile[1];
+      var x = Math.floor(xp*pixels.shape[0]);
+      var y = Math.floor(yp*pixels.shape[1]);
+
+      var R = pixels.get(x, y, 0);
+      var G = pixels.get(x, y, 1);
+      var B = pixels.get(x, y, 2);
+
+      var height = -10000 + ((R * 256 * 256 + G * 256 + B) * 0.1);
+
+      return cb(null, height);
+
+    });
+  }
+}
+

package.json

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+{
+  "dependencies": {
+    "@mapbox/tilebelt": "^1.0.1",
+    "get-pixels": "^3.3.0"
+  },
+  "name": "mapbox-elevation",
+  "version": "1.0.0",
+  "description": "qucikly get the elevation of any lng,lat in the world",
+  "main": "index.js",
+  "directories": {
+    "test": "test"
+  },
+  "devDependencies": {},
+  "scripts": {
+    "test": "node test/test.js"
+  },
+  "keywords": [
+    "mapbox",
+    "elevation",
+    "terrain",
+    "height",
+    "depth"
+  ],
+  "author": "Matthew Chase Whittemore",
+  "license": "ISC"
+}

test/test.js

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+var MapboxElevation = require('..');
+
+var getElevation = MapboxElevation(process.env.MAPBOX_PUBLIC_TOKEN);
+
+getElevation([0,0], function(err, elevation) {
+  if (err) throw err;
+  console.log('elevation at null island', elevation);
+});
+
+getElevation([-71.3030925, 44.270171], function(err, elevation) {
+  if (err) throw err;
+  console.log('elevation in mt washington nh', elevation);
+});
+
+getElevation([86.925313, 27.988730], function(err, elevation) {
+  if (err) throw err;
+  console.log('elevation at the peak of everest', elevation);
+});
+