A method, an antenna, and a system for determining positions for reflectio n points using microwaves. An electromagnetic wave signal is generated at a defined frequency, and transmitted by an antenna unit. the antenna unit includes a transmitter antenna and a plurality of receiver antennas, separated by a kno wn spacing perpendicular to a main line of sight and devised to receive reflect ed portions of the transmitted wave. Phase comparator means are connected to th e transmitter antenna and the receiver antennas, and a control unit connected to the phase comparator means is operable to calculate an angle to a reflection poi nt from detected phase difference between at least two receiver antennas and the spacing between said at least two receiver antennas, and to calculate a distance to the reflection point from detected phase difference between the transmitter antenna and a receiver antenna dependent on the frequency.