Determining Current Location via Cell ID
Determining the current location of a device without an integrated GPS or Bluetooth GPS receiver is possible by retrieving the cell ID of the operator's cell which the phone is associated to. The accuracy however of using this method, compared to a standard GPS receiver, is much lower and varies from 100-500 meters for urban areas, down to 10 km for rural areas. The cell ID is the unique identifier of a base station within the same mobile phone network. Using a different operator from the same location means that the device is associated to a different cell. Association between the cell ID and the current location is made by using the API, which makes it easy to retrieve more relevant information such as the device's coordinates. A-GPS (Assisted GPS) retrieval is also possible by using this method.
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Device Requirements
This method is supported on Series 40 devices starting from Java Runtime 1.0.0 for Series 40. Symbian devices do not support this method.
For more information about the supported device models which use Java Runtime 1.0.0 for Series 40, please visit the device specifications on Nokia Developer web site here: Series 40 devices with Java Runtime 1.0.0
Determining whether a device supports cell ID location retrieval on runtime
Retrieving location via cell ID on a device that doesn't satisfy the above requirement, will throw a "NoClassDefFoundError" and terminate the MIDlet's execution. There are two ways to identify on runtime, whether a device supports this method of location retrieval or not:
- By catching the NoClassDefFoundError as shown below
- By retrieving the availability of the network, with the following System property:
System.getProperty("com.nokia.mid.networkavailability");
The above property, like the cell ID retrieval itself, is introduced in Java Runtime 1.0.0 for Series 40. Retrieving the property on Series 40 devices that do not support Java Runtime 1.0.0, will result in a null value, which is also an indication that the device doesn't support cell ID retrieval. What is more, the value of this property on devices that support Java Runtime 1.0.0 for Series 40, can inform about the availability of the network. If a network is available, a cell ID retrieval can be attempted.
These are the following possible return values of the above property and their meanings:
| Return String Value | Actual Case |
|---|---|
| null | The device does not support neither Java Runtime 1.0.0 for Series 40 and therefore nor cell ID retrieval |
| available | The device supports Java Runtime 1.0.0 for Series 40 and therefore cell ID retrieval. There is network coverage |
| unavailable | The device supports Java Runtime 1.0.0 for Series 40 and therefore cell ID retrieval. There is no network coverage or no SIM Card is inserted |
Determining retrieval method
Getting the device's current location via cell ID is done similarly to a GPS location retrieval by using a location provider object and extracting it's location object. The following retrieval methods can be used:
//Online cell ID and/or WLAN
int[] methods = {(Location.MTA_ASSISTED | Location.MTE_CELLID | Location.MTE_SHORTRANGE | Location.MTY_NETWORKBASED)};
//Assisted GPS
int[] methods = {(Location.MTA_ASSISTED | Location.MTE_SATELLTITE | Location.MTY_TERMINALBASED)};
//Standalone GPS
int[] methods = {(Location.MTA_UNASSISTED | Location.MTE_SATELLTITE | Location.MTY_TERMINALBASED)};
//Offline cell ID
int[] methods = {(Location.MTA_UNASSISTED | Location.MTE_CELLID | Location.MTY_TERMINALBASED)};
The retrieval of the location provider is made via a call to the getLocationProvider() method of the LocationUtil class:
provider = LocationUtil.getLocationProvider(methods, null);
Differences between frequent Cell-ID and GPS based location updates
One important difference between a Cell-ID based and a GPS based location provider, is that it is not possible to set a Location Listener to the Cell-ID based provider for listening to frequent location updates as one could do with the GPS based provider. Since the same provider class is used in both Cell-ID and GPS location retrievals, the setLocationListener method can be called by objects that use these two different location retrieval methods. Even though this is syntactically correct, the setLocationListener method has not been implemented for Cell-ID based providers. The only way to update the user's current location in a Cell-ID based scenario, is to call the getLocation method within a repeating thread.
Implementing the main MIDlet
import com.nokia.mid.location.LocationUtil;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
import javax.microedition.lcdui.Form;
import javax.microedition.location.LocationProvider;
import javax.microedition.location.Location;
import javax.microedition.location.LocationException;
import javax.microedition.location.QualifiedCoordinates;
public class GetCellIdCoordinates extends MIDlet implements Runnable, CommandListener
{
LocationProvider provider;
Location location;
QualifiedCoordinates coordinates;
Thread t;
Form f;
Display display;
Command exitCommand=new Command("Exit", Command.EXIT,0);
protected void startApp() throws MIDletStateChangeException
{
display = Display.getDisplay(this);
f=new Form("Current Location!");
f.append("Getting current location by using Cell ID...");
f.addCommand(exitCommand);
f.setCommandListener(this);
display.setCurrent(f);
t=new Thread(this);
t.start();
}
protected void destroyApp(boolean unconditional)
throws MIDletStateChangeException {
}
protected void pauseApp() {
}
public void run()
{
try {
//Specify the retrieval method to Online/Cell-ID
int[] methods = {(Location.MTA_ASSISTED | Location.MTE_CELLID | Location.MTE_SHORTRANGE | Location.MTY_NETWORKBASED)};
// Retrieve the location provider
provider = LocationUtil.getLocationProvider(methods, null);
location=provider.getLocation(50000);
coordinates=location.getQualifiedCoordinates();
f.deleteAll();
f.append("Latitude:"+coordinates.getLatitude()+"\n");
f.append("Longitude:"+coordinates.getLongitude());
} catch (NoClassDefFoundError ex)
{
f.deleteAll();
f.append("Cell-ID retrieval not supported on this device");
} catch(InterruptedException e)
{
f.deleteAll();
f.append("Location retrieval was interrupted");
} catch(LocationException x)
{
f.deleteAll();
f.append("Location could not be retreived");
}
}
public void commandAction(Command c, Displayable d) {
if(c==exitCommand)
{
try {
destroyApp(false);
notifyDestroyed();
}
catch (MIDletStateChangeException ex) {
}
}
}
}
Resources
The source file as well as the binaries can be downloaded from here: File:GetCellIdCoordinates.zip
See also
Article Metadata
Code Example
Tested with
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Article
Contents
NikhilVS - How to import locationUtil class
How can I import com.nokia.mid.location.LocationUtil class?NikhilVS 14:22, 3 October 2012 (EEST)
Hamishwillee - @NikhilVS - what do you mean
What do you mean? Import as shown in the example. If you download the zip and try it out the code above in the emulator of the Nokia Java SDK v2.0 IDE it "just works".
Regards
Hamishhamishwillee 06:54, 4 October 2012 (EEST)
Susmitha.m@ayansys.com - how to download the api
how to download the apisusmitha.m@ayansys.com 07:06, 3 November 2012 (EET)
Hamishwillee - @Susmitha.m@ayansys.com - what do you mean?
The API is available for use on the SDK and on devices. No separate download required. Test using the zip up in the ArticleMetaData.hamishwillee 07:47, 6 November 2012 (EET)
DownJuu - handling security exceptions when using location services
I have been looking at the WeatherApp example in the Nokia projects which seems to be using a similar method for retrieving the user location. How does one handle security exceptions in such a case because I have tried to run the WeatherApp example and when I deny the app to use location services, the phone hangs and seems to restart. I am using a Nokia c2-03DownJuu 17:16, 25 November 2012 (EET)
Hamishwillee - Ask on the java forums?
Hi DownJuu
I appreciate that this is "somewhat" related to this topic. However you're probably better off asking the question on the java discussion boards, or even on the WeatherApp discussion boards to get more "eyes" on the problem.
Regards
Hamishhamishwillee 03:09, 26 November 2012 (EET)
Centrepoint - Required Midlet Permissions
Hi
We developed a Java app that uses LocationUtil to get the location via Cell-ID. The unsigned app achieves this correctly on real S40 devices but the (Nokia) signed app doesn't.
We presume that we didn't request the necessary permissions in the JAD file but we can't readilly identify which ones might be required. As it isn't possible to install our own self-signed development certificate in the root store of a real S40 device we can't even determine this by trial and error.
The app already lists the 'javax.microedition.location.Location' permission as being required but. we suspect, additional permission(s) are necessary to enable the framework to send and receive messages over the network.
Please, does anyone have a definitive answer?
Many thanks
PeterCentrepoint 14:02, 4 January 2013 (EET)