You may use this code to direct users to Settings, where they can enable GPS:
locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
if( !locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) ) {
new AlertDialog.Builder(context)
.setTitle(R.string.gps_not_found_title) // GPS not found
.setMessage(R.string.gps_not_found_message) // Want to enable?
.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialogInterface, int i) {
owner.startActivity(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS));
}
})
.setNegativeButton(R.string.no, null)
.show();
}