DB, you are incorrect. I can think of a number of scenarios where the ground on the approach is at a higher elevation than the threshold thus presenting a radalt indication of less than 200ft. The ICAO standard for MSD in the final approach segment involves a complex calculation which generally employs specialist modelling software, but the absolute minimum obstacle clearance on a precision approach within the final approach segment would be in the order of 130ft. ICAO DOC 8168 Vol II, Part II, Ch 1 refers.
PS. I concur with the rest.
