A method of pulsed radar interface determination for a first and second material in a tank. An interface level determination model is provided including a transfer function that utilizes refractive indices for the materials and thickness of the second material. At least one actual radar pulse is transmitted into the tank and a resulting echo curve portion including a measured interface pulse(s) around the interface location is measured. The interface model is simulated with a reference pulse and an initial thickness value to generate an initial model generated interface pulse (initial MGIP). The measured interface pulse is compared to the initial MGIP pulse point-by-point to determine residuals. If the residuals sum >a predetermined threshold, the comparing is repeated with an updated interface model generated with an updated thickness value that provides an updated MGIP pulse. When the sum of residuals is ≤predetermined threshold, the thickness is determined.