After recieving the NM and the CA code the reciever calculates its position by looking at the time delay between the sending and recieving of signal.
Am I right in thinking that the pseudorange is a 3d sphere?
That and with reference to the speed of light. The receiver calculates these and applies errors first for each of the information received from 3 satellites (for a 2D solution) and 4 satellites (for 3D solution). Newer GPS receivers have 12 channels so in addition to the 4 used to lock onto the satellites, the other 8 is used to lock onto additional satellites for more accuracy.
I am not sure but I think the pseudo range is calculated first using 3 satellites, thus a 2D sphere. Only after azimuth and elevation data received from the 3 satellites and error corrections are made for the 2D position, information from additional satellites are used for 3D modelling.
Correct me if I am wrong.