On Day 9: We'll see how to use Location API to get user location from application with both: 1. GPS 2. Network

1. Android Application Development
GPS Access
Ahsanul Karim
ahsanul.karim@sentinelbd.com
Sentinel Solutions Ltd.
http://www.sentinelbd.com

2. GPS Technology: Simplified
• The Global Positioning System (GPS) is a satellite-based navigation system made
up of a network of 24 satellites placed into orbit by the U.S. Department of Defense.
• GPS was originally intended for military applications, but in the 1980s, the
government made the system available for civilian use.
• GPS works in any weather conditions, anywhere in the world, 24 hours a day.
• There are no subscription fees or setup charges to use GPS.

3. GPS Technology: Simplified (Contd.)
• Global Positioning System satellites transmit signals to equipment (receivers)
on the ground. GPS receivers passively receive satellite signals; they do not
transmit.
• GPS receivers require an unobstructed view of the sky
• Depend on a very accurate time reference, which is provided by atomic clocks
at the U.S. Naval Observatory. Each GPS satellite has atomic clocks on board.
• Each GPS satellite transmits data that indicates its location and the current
time.
• All GPS satellites synchronize operations so that these repeating signals are
transmitted at the same instant.
• The signals, moving at the speed of light, arrive at a GPS receiver at slightly
different times because some satellites are farther away than others.
• The distance to the GPS satellites can be determined by estimating the amount
of time it takes for their signals to reach the receiver.
• When the receiver estimates the distance to at least four GPS satellites, it can
calculate its position in three dimensions.
• There are at least 24 operational GPS satellites at all times. The satellites,
operated by the U.S. Air Force, orbit with a period of 12 hours.

4. GPS Technology: Determining Position

5. GPS Access
1. Create a project Named “UseGps”
2. We need to add some permissions to use GPS and Internet

6. GPS Access
3. Now we need add a location listener, so each time the GPS senses a new location,
this callback function will be called from the android system.
To do this, we need to add the fallowing code in the onCreate() method:

7. GPS Access
4. We now have to create MyLocationListener class that implements LocationListener and
Implement methods for various events:
· onLocationChanged ( Location Update )
· onProviderDisabled ( GPS Off )
· onProviderEnabled (GPS On )

8. GPS Access

9. GPS Access
5. Now we run the app in emulator and use emulator control to emulate the GPS module

10. GPS Access
6. Now we’ll add a webview to main.xml layout and show the location in a map
7. Capture the webview by findViewById()

11. GPS Access
8. Now when the location is changed
9. Lets run it again

12. GPS Access