Longitude an latitude values are not updating.

I'm trying to create a GPS model so that I can later add it to a vehicle simulation. I've looked at the gps test_world file to see how I can add GPS to my model, which is just a cube. I'm getting velocity values but my longitude and latitude values are not changing. Can anyone help?0 0 0 0 0 010.0true01310.501311.000.10.10.10.100.20.20.20.2 sensor is this case is a child of link