The invention relates to a method (METH) for measuring a distance R between a vehicle (V) and an identifier (I) for accessing and starting the vehicle (V), the vehicle (V) and the identifier (I) being synthronised. The method (METH) comprises the following steps: —selecting (Sel_fp) N frequencies fp, pϵ[1;N], N being a natural number at least higher than 3; —implementing N sequences Sqp, each sequence Sqp comprising the following steps: •transmitting (Em_Svp) a first signal (Svp) of frequency fp from an emitter (TXv) of the vehicle (V) to a receiver (Rxi) of the identifier (I); •measuring (Mes_ϕvip) with a calculator (Xi) of the identifier (I) a phase ϕvip, modulo 2π, of the first signal (Svp) received, relative to a second signal (Sip) of phase ϕip(t)=ϕ0ip+2πfpt; •transmitting (Em_Sip) the second signal (Sip) from an emitter (TXi) of the identifier (I) to a receiver (RXv) of the vehicle (V); •calculating (Mes_ϕivp) with a calculator (Xv) of the vehicle (V) a phase ϕivp, modulo 2π, of the second signal (Sip) received, relative to the first signal (Svp); •calculating (Cal_ϕp) the average ϕp of the phase ϕvip and of the phase ϕivp; —for each p between 1 and N−1, calculating (Cal_Pp) a ramp Pp using the formula Pp=(ϕp+1−ϕp)/(fp+1−fp); and—calculating (Cal_R) distance R front the ramps Pp, pϵ[1;N].