A method for operating a radar altimeter, the method comprising: transmitting a radar signal at a first frequency for a first length of time; ramping the frequency of the radar signal from the first frequency to a second frequency; transmitting the radar signal at the second frequency for a second length of time; receiving reflections of the radar signal; processing the reflections by: determining an approximate distance to a target from which the reflections are received based on an amount of time between transmission of the radar signal having the frequency ramp and reception of a reflection of the radar signal having the frequency ramp; characterized by determining a first phase of a reflection of the radar signal transmitted at the first frequency, wherein the first phase is the phase of the radar signal as received; determining a second phase of a reflection of the radar signal transmitted at the second frequency, wherein the second phase is the phase of the radar signal as received; calculating a phase difference between the first phase and the second phase; and refining the approximate distance to the target based on the phase difference between the first phase and the second phase, wherein refining the approximate distance includes calculating a refined distance based on the phase difference divided by 360 degrees and multiplied by a maximum unambiguous distance, where the maximum unambiguous distance is the speed of light divided by two times the frequency difference between the first frequency and the second frequency. transmitting a radar signal at a first frequency for a first length of time; ramping the frequency of the radar signal from the first frequency to a second frequency; transmitting the radar signal at the second frequency for a second length of time; receiving reflections of the radar signal; processing the reflections by: determining an approximate distance to a target from which the reflections are received based on an amount of time between transmission of the radar signal having the frequency ramp and reception of a reflection of the radar signal having the frequency ramp; characterized by determining a first phase of a reflection of the radar signal transmitted at the first frequency, wherein the first phase is the phase of the radar signal as received; determining a second phase of a reflection of the radar signal transmitted at the second frequency, wherein the second phase is the phase of the radar signal as received; calculating a phase difference between the first phase and the second phase; and refining the approximate distance to the target based on the phase difference between the first phase and the second phase, wherein refining the approximate distance includes calculating a refined distance based on the phase difference divided by 360 degrees and multiplied by a maximum unambiguous distance, where the maximum unambiguous distance is the speed of light divided by two times the frequency difference between the first frequency and the second frequency. determining an approximate distance to a target from which the reflections are received based on an amount of time between transmission of the radar signal having the frequency ramp and reception of a reflection of the radar signal having the frequency ramp; characterized by determining a first phase of a reflection of the radar signal transmitted at the first frequency, wherein the first phase is the phase of the radar signal as received; determining a second phase of a reflection of the radar signal transmitted at the second frequency, wherein the second phase is the phase of the radar signal as received; calculating a phase difference between the first phase and the second phase; and refining the approximate distance to the target based on the phase difference between the first phase and the second phase, wherein refining the approximate distance includes calculating a refined distance based on the phase difference divided by 360 degrees and multiplied by a maximum unambiguous distance, where the maximum unambiguous distance is the speed of light divided by two times the frequency difference between the first frequency and the second frequency.