IRlock pixel to position formula

Hello all. Currently i am working on a tracking a moving car using the IR-Lock. So far its working fine, but needs some improvements. So i wonder if someone could explain to me where can i get the formula that is used to convert the IRLock pixels into position. I googled it and tried to search for anything but could’t find anything related to it.

You can find the code here

and name of the function : pixel_to_1M_plane