Every 12 hrs a weather balloon is released all around the world. The balloons provide the data used to make the countries weather forecasts. The weather balloon system has been in affect since WW II. We use weather balloons to gather info on temperature, pressure, relative humidity, and wind velocity. There are 70 weather balloon launch sites in the U.S. and 700 in the world.
The weather balloons are made of rubber and are inflated with either helium or hydrogen to a diameter of about 2 meters. An instrument package is attached to each balloon by a 15 meter cord. While the balloons are aloft the devices in the balloons record data and transmit it.
1.Satellites aren't exact because they are to far out into space and weather balloons are right in the sky.
2.He must know them in order to fill up the weather balloon.

http://www.islandnet.com/~see/weather/graphics/wxdrphotos/wxballoon3.jpg----this is my picture