Getting Started with GEO, CouchDB, and Node.js

Getting Started with GEO, CouchDB, and Node.js

Mick Thompson

Language: English

Pages: 66

ISBN: 1449307523

Format: PDF / Kindle (mobi) / ePub

Today's mobile devices have GPS and standard APIs to give you access to coordinates—but what can you do with that data? With this concise book, application developers learn how to work with location data quickly and easily, using Node.js, CouchDB, and other open source tools and libraries.

Node.js makes it simple to run event code on the Web, and the CouchDB document-oriented database lets you store location data and perform complex queries on it quickly. You'll learn how to get started with these tools, and then use them together to build an example project called MapChat, using HTML and JavaScript code samples.

  • Learn how to serve dynamic content with Node.js, and use its asynchronous IO to handle several requests at once
  • Become familiar with GeoJSON, Geohash, and the Geospatial Data Abstraction Library (GDAL) for working with spatial data
  • Build geospatial indexes using the GeoCouch branch of CouchDB
  • Combine these tools to build a project that lets users post real-time chat messages tagged with their current map location

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with the request: &text=kitty+cat&has_geo=true&extras=geo&per_page=1000& format=json&nojsoncallback=1 JSON Response: { "photos": { "page": 1, "pages": "116", "perpage": "500", "total": "57870", "photo": [ { "id": "5845159255", "owner": "11032335@N00", "secret": "4f81b07060", "server": "2778", "farm": 3, "title": "Wolfie enjoys his carpet tunnel", "ispublic": 1, "isfriend": 0, "isfamily": 0, "latitude": 37.33847,

for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords. Constant width bold Shows commands or other text that should be typed literally by the user. Constant width italic Shows text that should be replaced with user-supplied values or by values determined by context. vii This icon signifies a tip, suggestion, or general note. This icon indicates a warning or

is returned by the createServer function: var express = require("express"), app = express.createServer(), io = require(""); socket = io.listen(app); It is that simple to set up to work with ExpressJS. Now to set up the rest of the web app. The application will need to serve some static files for the JavaScript and stylesheet as well as a couple of images. To do this, add a static handler. Everything on a path that starts with “/static” will be served from a directory named

4: MapChat - Example Project Getting User Location Modern browsers allow JavaScript to request the user’s current location. The browsers all then ask if the user wants to share their location with the current website. Not all of the users will allow location, nor will all browsers support it. In MapChat if the browser doesn’t support returning location, or if the user does not allow it, the map will default to a central location. Another option would be to add a lookup using the user’s IP

MapChat will use the recentPoints spatial view. When querying for clustered chat locations, that data should be sent to all connected clients, as well as cached for new clients. Notify Clients of Cluster Updates First, add a send function to the MapChat server: maphat = { //subscribe:function()... }; sendChatClusters: function(client){ if(client != undefined){ // Send to just the one client client.send({"type":"clusters", "clusters":mapchat.clusters}); }else{ // Send to all subscriptions for(s

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