外文文献原文GPS的精确使用.docx

How accurate is Android GPS? Part 1: Understanding Location Databyagup Posted: Sunday, 1/27/2013There are many different ways for developers to get access to location information using the Android SDK, and there are already plenty of code examples on the internet showing how to do that. This post, on the other hand, focuses on putting the location data into context and offers suggestions on how to use it in the best possible way. In this series I’ll discuss various aspects of the Android SDK’s android.location package and how you can best take advantage of them to build a great end-user experience.To try out GPS different usage scenarios, be sure to download the GPSTester app, both the .apk and source code are available on github.Six types of location dataIt’s not just about latitude and longitude. The great thing about the Android SDK is you get access to a ton of information related to location. The fun, challenging and sometimes frustrating part is deciphering the information. There are six types of location data that you have programmatic access to. This data comes from what’s referred to as a provider, and it will be either a cellular network-based or a GPS provider. As you’ll see, you can use these providers in a variety of different ways.All locations derived from the LocationManager are guaranteed to provide a valid latitude, longitude and timestamp, all the other parameters are optional depending on who manufactured the handset and who is providing cellular service. However, if you have a device that doesn’t give you access to the accuracy parameter then the location data is practically worthless. I haven’t come across such a device yet, but I’m assuming it’s possible. My advice: always check for null location parameter values in your production code.Cached GPS. Most Androids have the ability to store the last know GPS location. This is typically used when an application first starts up, and you can retrieve the timestamp, latitude, longitude and accuracy.1