Method to determine a position of an apparatus comprising: a first step of determining; a first distance between the apparatus and a beacon, at a first instant and a first position (A(x A, y A)) of the beacon, at the first instant and a second distance (DC or AC) between the apparatus and the beacon, at a second instant and a first length of a first straight line going from a position of the apparatus at the first instant and a position of the apparatus at the second instant and a first angle ( α) between a first axis and a first direction of the first straight line and a third distance (EF or AF) between the apparatus and the beacon at a third instant and a second length of a second straight line going from a position of the apparatus at the first instant and a position of the apparatus at the third instant and a second angle ( β) between the first axis and a second direction of the second straight line and, eventually a second position (D(x D, y D)) of the beacon at the second instant and, eventually a third position (E(x E, y E)) of the beacon at the third instant, the method also comprising a second step of determining at least two possible positions ( B 1, B 2) of the apparatus based on; the first distance and the second distance ( DC or AC) and the first length and the first angle ( α) and the first position (A(x A, y A)) and eventually the second position (D(x D, y D)) and a third step of determining at least two other possible positions ( B 3, B 4) of the apparatus based on; the first distance and the third distance (EF or AF) and the second length and the second angle ( β) and the first position (A(x A, y A)) and eventually the third position (E(x E, y E)), and a fourth step of determining the position of the apparatus by calculating distances between couples of different possible positions ( B 1, B 2, B 3, B 4) and by determining the position based on the couple with minimal distance. a first step of determining; a first distance between the apparatus and a beacon, at a first instant and a first position (A(x A, y A)) of the beacon, at the first instant and a second distance (DC or AC) between the apparatus and the beacon, at a second instant and a first length of a first straight line going from a position of the apparatus at the first instant and a position of the apparatus at the second instant and a first angle ( α) between a first axis and a first direction of the first straight line and a third distance (EF or AF) between the apparatus and the beacon at a third instant and a second length of a second straight line going from a position of the apparatus at the first instant and a position of the apparatus at the third instant and a second angle ( β) between the first axis and a second direction of the second straight line and, eventually a second position (D(x D, y D)) of the beacon at the second instant and, eventually a third position (E(x E, y E)) of the beacon at the third instant, the method also comprising a second step of determining at least two possible positions ( B 1, B 2) of the apparatus based on; the first distance and the second distance ( DC or AC) and the first length and the first angle ( α) and the first position (A(x A, y A)) and eventually the second position (D(x D, y D)) and a third step of determining at least two other possible positions ( B 3, B 4) of the apparatus based on; the first distance and the third distance (EF or AF) and the second length and the second angle ( β) and the first position (A(x A, y A)) and eventually the third position (E(x E, y E)), and a fourth step of determining the position of the apparatus by calculating distances between couples of different possible positions ( B 1, B 2, B 3, B 4) and by determining the position based on the couple with minimal distance.