A navigation device , comprising: a) an altimeter including a pressure sensor ; b) a radio ; c) a memory including program instructions; and d) a controller operably connected to the pressure sensor, the radio, and the memory and configured to execute the program instructions to 1.1 receive at least one signal broadcasted from a beacon selected by determining which beacon is nearest to the navigation device as a reference beacon of a plurality of beacons (208, 212, 232, 236; 216, 220), the signal from the reference beacon including the best available reference atmospheric pressure data, and to determine the reference altitude corresponding to the best available reference atmospheric pressure data broadcast by the reference beacon; 1.2 determine a reference relationship curve correction based upon the received at least one signal, the reference relationship curve correction including calibrating the altimeter by aligning of a reference relationship curve describing the relationship between atmospheric pressure and altitude with a point on the graph that corresponds to the best available reference atmospheric pressure data and the reference altitude, and 1.3 determine an altitude of the navigation device based upon (i) the corrected reference relationship curve, and (ii) a pressure signal from the pressure sensor. a) an altimeter including a pressure sensor ; b) a radio ; c) a memory including program instructions; and d) a controller operably connected to the pressure sensor, the radio, and the memory and configured to execute the program instructions to 1.1 receive at least one signal broadcasted from a beacon selected by determining which beacon is nearest to the navigation device as a reference beacon of a plurality of beacons (208, 212, 232, 236; 216, 220), the signal from the reference beacon including the best available reference atmospheric pressure data, and to determine the reference altitude corresponding to the best available reference atmospheric pressure data broadcast by the reference beacon; 1.2 determine a reference relationship curve correction based upon the received at least one signal, the reference relationship curve correction including calibrating the altimeter by aligning of a reference relationship curve describing the relationship between atmospheric pressure and altitude with a point on the graph that corresponds to the best available reference atmospheric pressure data and the reference altitude, and 1.3 determine an altitude of the navigation device based upon (i) the corrected reference relationship curve, and (ii) a pressure signal from the pressure sensor. 1.1 receive at least one signal broadcasted from a beacon selected by determining which beacon is nearest to the navigation device as a reference beacon of a plurality of beacons (208, 212, 232, 236; 216, 220), the signal from the reference beacon including the best available reference atmospheric pressure data, and to determine the reference altitude corresponding to the best available reference atmospheric pressure data broadcast by the reference beacon; 1.2 determine a reference relationship curve correction based upon the received at least one signal, the reference relationship curve correction including calibrating the altimeter by aligning of a reference relationship curve describing the relationship between atmospheric pressure and altitude with a point on the graph that corresponds to the best available reference atmospheric pressure data and the reference altitude, and 1.3 determine an altitude of the navigation device based upon (i) the corrected reference relationship curve, and (ii) a pressure signal from the pressure sensor. <EOS>