What is Geotagging?
Geotagging or geocoding is a way to add geographical meta data to photos, RSS feeds, and websites. A geotag can define the longitude and latitude of the tagged item. Or it can define the location place name or regional identifier. It can also include information such as the altitude and bearing.
By placing a geotag on a Web page, website, or RSS feed, you provide information to your readers and to search engines about the geographical location of the site. It can also refer to the location that the page or photo is about. So if you wrote an article about the Grand Canyon in Arizona, you could tag it with a geotag indicating that.
How to Write Geotags
The easiest way to add geotags to a Web page is with meta tags. You create a ICBM meta tag that includes the latitude and longitude in the contents of the tag:
<meta name="ICBM" content="48, -122" />
You can then add other meta tags that include the region, placename, and other elements (altitude, etc). These are named "geo.*" and the contents are the value for that tag. For example:
<meta name="geo.region" content="US-WA" /> <meta name="geo.placename" content="Snohomish" /> <meta name="geo.position" content="48;-122" />
Another way you can tag your pages is to use the Geo microformat. There are only two properties in the Geo microformat: latitude and longitude. To add it to your pages, simply surround the latitude and longitude information in a span (or any other XHTML tag) with the title "latitude" or "longitude" as appropriate. It's also a good idea to surround the entire location with a div or span with the title "geo". For example:
<div class="geo">GEO: <span class="latitude">37.386013</span>, <span class="longitude">-122.082932</span> </div>
It's easy to add geotags to your sites.
Who Can (or Should?) Use Geotagging?
Before you dismiss geotagging as a fad or something that only "other people" should do, you should consider what types of sites you build and how geotagging can be used to enhance them.
Geotagging Web pages is ideal for retail sites and tourism sites. Any website that has a physical storefront or location can benefit from geotags. And if you get your sites tagged early, they are likely to rank higher in geotagged search engines than your competitors who scoffed and didn't tag their sites.
Web pages with geotags are already in use in a limited format on some search engines. Customers can come to the search engine, enter their location and find Web pages of sites that are near their current location. If your business is tagged, it's an easy way for customers to find your site. And now that more phones are coming equipped with GPS, they can get to your storefront even if all you provide are latitude and longitude.
But even more exciting are new sites that are coming online such as FireEagle. These are sites that track customer locations using cellphones and either GPS data or triangulation. If a customer of FireEagle has opted-in to receiving retail data, when they pass by a location that has been encoded with geo data, they can receive contacts directly to their cellphone. By geotagging your retail or tourist website, you set it up to connect with the customers who are broadcasting their location.
Protect Your Privacy and Use Geotags
One of the biggest concerns about geotagging is privacy. If you post the latitude and longitude of your house in your weblog, someone who disagrees with your post could come and knock on your door. Or if you always write your weblog from a coffee shop 3 miles away from your house, a thief might figure out you're not at home from your geotags and rob your house.
The nice thing about geotags is that you only need to be as specific as you feel comfortable with being. For example, the geotags I listed above in the meta tags sample are for where I live. But they are for the city and around 100km radius around my location. I feel comfortable with revealing that level of accuracy regarding my location, as it could be nearly anywhere in the county. I wouldn't feel comfortable with providing an exact latitude and longitude of my house, but geotags don't require that I do so.
As with many other privacy issues on the Web, I feel that the privacy concerns surrounding geotagging can be easily mitigated if you, the customer, takes the time to think about what you do and don't feel comfortable with. The thing you should be aware of is that location data is being recorded about you without your knowing it in many cases. Your cellphone provides location data to the cell towers near it. When you send email, your ISP provides data about where the email was sent from and so on. Geotagging gives you a little more control. And if you use a system like FireEagle, you'll be able to control who knows your location, how specific they can learn your location, and what they are allowed to do with that information.