The rainfall information showing in Rainsat is received from satellite observations, collected every 15-minutes. Rainsat shows the rainfall intensity from the previous 4 hours up to now and helps the user to see if more rain can be expected or not. Please note that the rainfall measured by satellites during daytime is more accurate than during the night, when it is dark and other observation techniques (only Thermal Infra Red) are used.
This app wants to use your GPS. Note that continued use of GPS running in the background can dramatically decrease battery life.