APC is a calibration system process that is done by using a quickly and accurately system to create a new value reading table. It can be implemented to both the old and the new fuel tank. Anyway, you only need to have an oil stock level as high as your highest tank capacity.
Normally when creating new tank value reader table, we use 200 liters tank to lap the water and pour into the tank that need to measure. Waiting until the water is stop moving then measure the height level of water. For one tank it will be used around 17-18 hours to finish the process.
Anyway, with APC system, the process will be automatically by draining fuel into the tank. Using ATG to measure the height level and volume of fuel in the tank. This process use only 4-6 hours and can read the value between 50-200 liters. So, it has high precision than the conventional method.