Method for locating a navigation unit in an environment containing beacons transmitting messages, this method comprising execution of the following steps for each time t k of a temporal sequence of times {t 0;...; t k-1; t k;...}: a) receiving messages transmitted by at least three beacons, then b) extracting raw measurements of pseudoranges separating the navigation unit from each of these at least three beacons based on the times of receipt of these messages as measured by the navigation unit and on the speed of propagation of these messages through space, c) estimating an internal position of the navigation unit at the time t k based on the raw measurements extracted for this time t k, on the preceding internal position of the navigation unit estimated at the time t k-1 and on the positions of the beacons, d) for a plurality of beacons, establishing a measurement bias for the time t k that, when it is subtracted from the raw measurement extracted based on the time of receipt of the message transmitted by this beacon, allows the error affecting this raw measurement to be decreased, this bias being established based on the difference between: - computed pseudorange separating this beacon from the navigation unit, this computed pseudorange being computed based on a position of this beacon and on the internal position of the navigation unit estimated for the time t k, and - measured pseudorange separating this beacon from the navigation unit, this measured pseudorange being computed based on the raw pseudorange measurement extracted for this beacon for the time t k and without taking into account the internal position of the navigation unit, e) for each beacon for which a measurement bias was established for the time t k, computing a corrected measurement of the pseudorange at the time t k by adding the bias established for this beacon to a raw measurement of the pseudorange for this beacon extracted at the time t k, characterized in that the method also comprises the following step: f) estimating an external position of the navigation unit at the time t k based on: - positions of the beacons for which a corrected measurement of the pseudorange at the time t k was computed, - corrected pseudorange measurements computed for the time t k, and - the preceding external position of the navigation unit estimated for the preceding time t k-1, and in which steps b), c) and d) are carried out without taking into account the external position of the navigation unit. a) receiving messages transmitted by at least three beacons, then b) extracting raw measurements of pseudoranges separating the navigation unit from each of these at least three beacons based on the times of receipt of these messages as measured by the navigation unit and on the speed of propagation of these messages through space, c) estimating an internal position of the navigation unit at the time t k based on the raw measurements extracted for this time t k, on the preceding internal position of the navigation unit estimated at the time t k-1 and on the positions of the beacons, d) for a plurality of beacons, establishing a measurement bias for the time t k that, when it is subtracted from the raw measurement extracted based on the time of receipt of the message transmitted by this beacon, allows the error affecting this raw measurement to be decreased, this bias being established based on the difference between: - computed pseudorange separating this beacon from the navigation unit, this computed pseudorange being computed based on a position of this beacon and on the internal position of the navigation unit estimated for the time t k, and - measured pseudorange separating this beacon from the navigation unit, this measured pseudorange being computed based on the raw pseudorange measurement extracted for this beacon for the time t k and without taking into account the internal position of the navigation unit, - computed pseudorange separating this beacon from the navigation unit, this computed pseudorange being computed based on a position of this beacon and on the internal position of the navigation unit estimated for the time t k, and - measured pseudorange separating this beacon from the navigation unit, this measured pseudorange being computed based on the raw pseudorange measurement extracted for this beacon for the time t k and without taking into account the internal position of the navigation unit, e) for each beacon for which a measurement bias was established for the time t k, computing a corrected measurement of the pseudorange at the time t k by adding the bias established for this beacon to a raw measurement of the pseudorange for this beacon extracted at the time t k, f) estimating an external position of the navigation unit at the time t k based on: - positions of the beacons for which a corrected measurement of the pseudorange at the time t k was computed, - corrected pseudorange measurements computed for the time t k, and - the preceding external position of the navigation unit estimated for the preceding time t k-1, and - positions of the beacons for which a corrected measurement of the pseudorange at the time t k was computed, - corrected pseudorange measurements computed for the time t k, and - the preceding external position of the navigation unit estimated for the preceding time t k-1, and in which steps b), c) and d) are carried out without taking into account the external position of the navigation unit.