Browser geolocation APIs

Many mobile web browsers provide access to the current geo location via JavaScript (see the W3C spec). It's very easy to use but there are a couple gotchas to be aware of. First, not all browsers support the API so you will need to take that into consideration when designing your user experience. Next, requesting the geo location from the browser will prompt the viewer to approve the request. On every page view. This is very annoying. You should store the location data away in a cookie and only periodically request updated location information. Another cool function is that the geolocation API allows your code to be notified as the location moves - perhaps your visitors take the bus or use their mobile devices while riding a bike. This is done with callbacks which is very compatible with client development and makes total sense.

Here is some sample script showing how you could use this geolocation API in your mobile or location aware web apps.

function onLocationUpdated(position)
{
  // do something useful
   savePosition(position);
  createCookie("s_geo","on",3600);
  updateLocationDisplay(position);
}

// request location
if (navigator.geolocation && !readCookie("s_geo"))
{
  navigator.geolocation.getCurrentPosition(onLocationUpdated);

  var watchID = navigator.geolocation.watchPosition(
  onLocationUpdated, null, {
    enableHighAccuracy : true,
    timeout : 30000
  });
}



geonote.org - sharing the world around you

Over the past month I've put together a mobile friendly web app which lets people share notes about the places they visit. Building the basic web app for storing and sharing notes about a place was pretty straightforward, but like any new application meant to be social the biggest problem is the empty room syndrome - if there is nothing to see, most people just wander off. It takes a special person to start sharing in an empty space.

Rather than try to build up functionality and features to attract a crowd, it seemed that showing information that already exists would be a good way to bootstrap the app. Since I originally envisioned this app as something like Wikipedia for places, but more of an open medium that people can use for any purpose they can put it to, I first thought to look at ways to index Wikipedia entries by their geo location. I quickly found that other folks had already done the indexing and provided an API - geonames.org Pulling this data in was pretty easy, they have a simple HTTP API that returns XML, which geonote.org simply formats into a mobile friendly display. Once there was a web app for sharing notes and viewing 'atlas' pages (the Wikipedia entries), I went in search of other location based APIs and found several great ones.

Here's the list of geo location APIs I've used so far

• GeoNames.org (Wikipedia entries and more) - http://www.geonames.org/export/ws-overview.html
• Flickr.com (Photos) - http://www.flickr.com/services/api/
• Plancast.com (Events) - http://groups.google.com/group/plancast-api/web/overview?pli=1
• Hunch (Recommendations) - http://hunch.com/developers/v1/
• Twitter (chitter chatter) - http://apiwiki.twitter.com/Twitter-API-Documentation

The Plancast crew especially was extremely helpful. Their forum described upcoming support for searching by latitude and longitude, but it had not been released at the time. After posting a comment they were able to build and release that feature in only a few days (on a weekend too!)
One of the most intriguing APIs was the Hunch API for recommendations. Although it has a lot of power, it requires a Twitter username to provide personalized recommendations and the geonote.org app is too simple to try to do real Twitter authentication integration. I'm sure to revisit the Hunch API though.