receiving at an asynchronous passive-listening TDoA device a first message transmitted from a first active device in a communication exchange with a second active device having a distance therebetween;

receiving at the asynchronous passive-listening TDoA device a second message transmitted from the second active device in reply to the first transmitted message;

receiving at the asynchronous passive-listening TDoA device a third message transmitted from the first active device in reply to the second transmitted message;

determining, by a processor of the asynchronous passive-listening TDoA device, a first time difference (R_T1) between a first measured time corresponding to receipt of the first message and a second measured time corresponding to receipt of the second message;

determining, by the processor, a second time difference (R_T2) between the second measured time corresponding to the receipt of the second message and a third measured time corresponding to receipt of the third message; and

determining, by the processor, a time difference of arrival (TDoA) value corresponding to the difference between the asynchronous passive-listening TDoA device to first active device distance and the asynchronous passive-listening TDoA device to second active device distance using

(i) the first time difference (R_T1) as observed by the asynchronous passive-listening TDoA device,

(ii) the second time difference (R_T2) as observed by the asynchronous passive-listening TDoA device,

(iii) one or more of (a) a time measures (D_A) defined between the receipt of the second message at the first active device and the transmission of the third message by the first active device, (b) a time measure (D_B) defined between the receipt of the first message at the second active device and the transmission of the second message by the second active device obtained by the asynchronous passive-listening TDoA device, and

(iv) at least one of (a) a time measure (R_A) defined between the transmission of the first message and the receipt of the second message at the first active device, (b) a time measure (R_B) defined between the transmission of the second message and the receipt of the third message at the second active device, or (c) a time measure (ρ_AB) corresponding to a time between when the first message was transmitted at the first active device and received at the second active device, according to at least one of: