A method for determining an angle of arrival 'AoA' of one or more RF signals received from an emitter at an antenna pair, comprising: receiving at a processor corresponding first and second components (305a, 305b) of a first signal detected at first and second antenna elements (215a, 215b) of the antenna pair, the antenna elements spaced apart by more than one half wavelength of the received signal components; determining one or more features of the received signal, including a phase difference between corresponding phases of the first and second signal components detected at the first and second antenna elements, and a time difference of arrival 'TDOA' between the signal components arriving at the first and second antenna elements, the TDOA having a known measurement uncertainty or error range; performing a TDOA angle calculation using the TDOA to obtain a TDOA error boundary comprising a range of TDOA AoA possibilities centered at a solution to the TDOA angle calculation and bounded by the known TDOA measurement error range; calculating a set of AoA estimates using phase interferometry 'PI' based on the phase difference of the first and second signal components measured at the first and second antenna elements, and within the TDOA AoA error boundary; and characterised in determining a precise AoA estimate by iteratively performing the steps of receiving signal components at the first and second antenna elements, determining the received signal component features, averaging the TDOA measurements, using the averaged TDOA measurements to re-compute the TDOA AoA error boundary with smaller error bounds, and, optionally, averaging the signal component phase differences and re-calculating the PI AoA estimate for one or more additional signals associated with the emitter. receiving at a processor corresponding first and second components (305a, 305b) of a first signal detected at first and second antenna elements (215a, 215b) of the antenna pair, the antenna elements spaced apart by more than one half wavelength of the received signal components; determining one or more features of the received signal, including a phase difference between corresponding phases of the first and second signal components detected at the first and second antenna elements, and a time difference of arrival 'TDOA' between the signal components arriving at the first and second antenna elements, the TDOA having a known measurement uncertainty or error range; performing a TDOA angle calculation using the TDOA to obtain a TDOA error boundary comprising a range of TDOA AoA possibilities centered at a solution to the TDOA angle calculation and bounded by the known TDOA measurement error range; calculating a set of AoA estimates using phase interferometry 'PI' based on the phase difference of the first and second signal components measured at the first and second antenna elements, and within the TDOA AoA error boundary; and characterised in determining a precise AoA estimate by iteratively performing the steps of receiving signal components at the first and second antenna elements, determining the received signal component features, averaging the TDOA measurements, using the averaged TDOA measurements to re-compute the TDOA AoA error boundary with smaller error bounds, and, optionally, averaging the signal component phase differences and re-calculating the PI AoA estimate for one or more additional signals associated with the emitter.