1. Maps, Geocoding, and
Location-Based Services

2. Maps, Geocoding, and Location-Based Services
USING LOCATION-BASED SERVICES
CONFIGURING THE EMULATOR TO TEST LOCATION-BASED SERVICES
UPDATING LOCATIONS IN EMULATOR LOCATION PROVIDERS
SELECTING A LOCATION PROVIDER

3. Location-Based Services
Introduction
Location-Based Services or LBS allow software to obtain the phone's current location. This includes location obtained from the Global Positioning System (GPS) satellite constellation and Google’s cell-based location technology.

4. Location-Based Services
Scenarios
Location based services can be used in so many different scenarios. Such examples include :
Ride Sharing
Meet Anywhere
Social networking/Mobile Social networking
Buddy Finder/ Friend finder
location based Advertisement
location based business locator
tourism guides with text popup in different locations
Navigation
Traffic management
Car Parking guide
Mobile games
Emergency Services

5. Location-Based Services
Limitations
Geographic Limitation. Most of the current geographic search engines are only limited to USA and Canada. Some of them have a wider coverage including UK, Australia, Japan, Taiwan and few more countries. Other search engines which have not been mentioned here are (also often limited to a city or country or even to a specific language.
Data Limitation. Existing location-based engines only cover commercially collected information of local businesses e.g. those mentioned in Yellow Pages. They do not cover World Wide Web although they might have link to those pages.
Performance Limitation. An ideal geographic search and presentation has not been supported by some available search engines and they can not match interactive maps with textual geographic data properly. For example, map-based query refinement is not guaranteed.

6. Location-Based Service
Location-Based Services
API Packages
The Location-Based API includes two packages android.location & com.google.android.maps that provide an initial look at the support in the Android platform for building location-based services.
Location-Based Service
android.location
com.google.android.map

7. Location-Based Services
LocationManager Class
LocationManager:
It provides an API to determine location and access to the system location services which allow applications to obtain periodic updates of the device's geographical location.
The application will be able to do three things:
Query for the list of all LocationProviders known to the LocationManager for its last known location.
Register/unregister for periodic updates of current location from a LocationProvider (specified either by Criteria or name).
Register/unregister for a given Intent to be fired if the device comes within a given proximity (specified by radius in meters) of a given lat/long.

8. Location-Based Services
Address, Criteria & Geocoder Class
Address Class
A class representing an Address, i.e, a set of Strings describing a location.
Criteria Class
A class indicating the application criteria for selecting a location provider. Providers maybe ordered according to accuracy, power usage, ability to report altitude, speed, and bearing, and monetary cost.
Geocoder Class
A class for handling geocoding and reverse geocoding. Geocoding is the process of transforming a street address or other description of a location into a (latitude, longitude) coordinate. Reverse geocoding is the process of transforming a (latitude, longitude) coordinate into a (partial) address.

9. UPDATING LOCATIONS IN EMULATOR LOCATION PROVIDERS
We can use the Location Controls available from the DDMS perspective in Eclipse to
push location changes directly into the emulator’s GPS Location Provider.
Using the Manual tab we can specify particular latitude/longitude pairs. Alternatively, the KML and GPX tabs let us load KML (Keyhole Markup Language) and GPX (GPS Exchange Format) files, respectively. Once these are loaded we can jump to particular waypoints (locations) or play back each location sequentially.

10. UPDATING LOCATIONS IN EMULATOR LOCATION PROVIDERS

11. SELECTING A LOCATION PROVIDER
Depending on the device, there may be several technologies that Android can use to determine the current location. Each technology, or Location Provider, will offer different capabilities, including differences in power consumption, monetary cost, accuracy, and the ability to determine altitude,
speed, or heading information.
To get an instance of a specific provider, call getProvider, passing in the name:
String providerName = LocationManager.GPS_PROVIDER;
LocationProvider gpsProvider;
gpsProvider = locationManager.getProvider(providerName);
This is generally useful only for determining the abilities of a particular provider. Most Location Manager methods require only a provider name to perform location-based services.

12. CHALLENGES IN DETERMINING USER LOCATION
Obtaining user location from a mobile device can be complicated. There are several reasons why a location reading (regardless of the source) can contain errors and be inaccurate. Some sources of error in the user location include:
Multitude of location sources GPS, Cell-ID, and Wi-Fi can each provide a clue to users location. Determining which to use and trust is a matter of trade-offs in accuracy, speed, and battery-efficiency.
User movement Because the user location changes, you must account for movement by re-estimating user location every so often.
Varying accuracy Location estimates coming from each location source are not consistent in their accuracy. A location obtained 10 seconds ago from one source might be more accurate than the newest location from another or same source.
These problems can make it difficult to obtain a reliable user location reading.

13. REQUESTING LOCATION UPDATES
This is how we can obtain user location on Android:
Getting user location in Android works by means of callback. You indicate that you'd like to receive location updates from the LocationManager ("Location Manager") by calling requestLocationUpdates(), passing it a LocationListener. Your LocationListener must implement several callback methods that the Location Manager calls when the user location changes or when the status of the service changes.

14. For example, the following code shows how to define a LocationListener and request location updates:
// Acquire a reference to the system Location Manager LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE); // Define a listener that responds to location updates LocationListener locationListener = new LocationListener() {     public void onLocationChanged(Location location) {       // Called when a new location is found by the network location provider.       makeUseOfNewLocation(location);     }     public void onStatusChanged(String provider, int status, Bundle extras) {}     public void onProviderEnabled(String provider) {}     public void onProviderDisabled(String provider) {}   }; // Register the listener with the Location Manager to receive location updates locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);

15. REQUESTING USER PERMISSIONS
In order to receive location updates from NETWORK_PROVIDER or GPS_PROVIDER, you must request user permission by declaring either the ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission, respectively, in your Android manifest file. For example:
<manifest ... >     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />     ... </manifest>
Without these permissions, your application will fail at runtime when requesting location updates.
Note: If you are using both NETWORK_PROVIDER and GPS_PROVIDER, then you need to request only theACCESS_FINE_LOCATION permission, because it includes permission for both providers. (Permission forACCESS_COARSE_LOCATION includes permission only for NETWORK_PROVIDER.)

16. Defining a Model for the Best Performance
Location-based applications are now commonplace, but due to the less than optimal accuracy, user movement, the multitude of methods to obtain the location, and the desire to conserve battery, getting user location is complicated. To overcome the obstacles of obtaining a good user location while preserving battery power, you must define a consistent model that specifies how your application obtains the user location. This model includes when you start and stop listening for updates and when to use cached location data.

17. Defining a Model for the Best Performance
 This timeline representing the window in which an application listens for location updates. This model of a window—during which location updates are received—frames many of the decisions you need to make when adding location-based services to your application.

18. DECIDING WHEN TO START LISTENING FOR UPDATES
You might want to start listening for location updates as soon as your application starts, or only after users activate a certain feature. Be aware that long windows of listening for location fixes can consume a lot of battery power, but short periods might not allow for sufficient accuracy.
As demonstrated above, you can begin listening for updates by calling requestLocationUpdates():
String locationProvider = LocationManager.NETWORK_PROVIDER; // Or, use GPS location data: // String locationProvider = LocationManager.GPS_PROVIDER; locationManager.requestLocationUpdates(locationProvider, 0, 0, locationListener);

19. Getting a fast fix with the last known location
The time it takes for your location listener to receive the first location fix is often too long for users wait. Until a more accurate location is provided to your location listener, you should utilize a cached location by calling getLastKnownLocation(String):
String locationProvider = LocationManager.NETWORK_PROVIDER; // Or use LocationManager.GPS_PROVIDER Location lastKnownLocation = locationManager.getLastKnownLocation(locationProvider);

20. Deciding when to stop listening for updates
The logic of deciding when new fixes are no longer necessary might range from very simple to very complex depending on your application. A short gap between when the location is acquired and when the location is used, improves the accuracy of the estimate. Always beware that listening for a long time consumes a lot of battery power, so as soon as you have the information you need, you should stop listening for updates by calling removeUpdates(PendingIntent):
// Remove the listener you previously added locationManager.removeUpdates(locationListener);