Best way to find Latitude and Longitude

I  want to find out whats the best way to write blocks to output Latitude and Longitude. I know there are several way to do this.  TO TEST, I wrote a small test app to output the Latitude and Longitude when the Screen Initializes and Location Sensor.changed. I clearly identified which test was what.   See screenshot below.

Not too sure why LocationSensor.changed worked over ScreenInitialized when I was inside a building? Is it because the location sensor in the Screen Initialize block, times out if location sensor doesn't find Lat & Long quick enough?

Also, should I state the provider? what are my options? GPS and Network? 

Have you read the LocationSensor tutorial and do you understand it?    http://appinventor.mit.edu/explore/ai2/tutorials3818.html?&page=2