Push and pull methods of location services

Location-based service implementations are either based on push services or pull services, depending on the way location information is retrieved.

Push service

Push services imply that the user receives location information without having to actively or continuously keep requesting it. However, the user's consent is acquired beforehand. For example, the navigation software in your car will require your consent to use your location information when you switch it on, however, as you drive your car around town, your new location will automatically be acquired via push services.

Some more examples of push services include the Emergency Alert System (in case of terror attacks) and location-based advertising apps on your phone that notify you with deals, messages, and alerts on entering a new city or town.

Pull service

Pull services work on the on demand principle; your apps would request location information from the network on demand. For example, if you use the Local Scout app (http://www.microsoft.com/windowsphone/en-us/howto/wp7/web/local-scout.aspx) on your Nokia Lumia 800, the Windows Phone 7.5 OS would request location information when it loads. Also you can change the location via the Settings page of the app. This way, the application pulls location information when it needs to, and not continuously.

In the forthcoming chapters, we will be building apps mostly using the pull services, including a local news app and an events app that will pull location information on demand, and mash it with information retrieved via web services.

Note

This type of location retrieval is also good for the battery power consumption of your phone, as GPS positioning involves a significant amount of battery power.