MODE C decoding

Hi, My name is Allan an I am currently working on my final year project for college. The idea is to create a radar system that interprets MODE C interrogation signals and replies by aircraft and SSR and with this information determine where these airplanes are in your vicinity. The device I am using to receive these transmissions is a DVB-T dongle. I will have to create an algorithm that will use the ping of the above transmissions which I am aware of. My problem is that I am having difficulty understanding how I will decode the signal to read the altitude and differentiate between other aircraft transmitting on the 1090MHz frequency. Could anyone in this forum point me in some direction as to how to learn this? Also apologies if I am unclear. Regards Allan