A ranging system, comprising: a first ranging unit comprising: a first laser driver (23, 33, 43, ..., n3); a first control circuit (22, 32, 42, ..., n2) configured to generate a first trigger signal; and a first data interface (21, 31, 41, ..., n1) comprising a first trigger transmitter configured to transmit the first trigger signal over a first data transmission line; and a second ranging unit comprising: a second laser driver (33, 43, ..., n3); a second data interface (31, 41, ..., n1) comprising a second trigger receiver configured to receive the first trigger signal over the first data transmission line ; characterized in that the first data interface (21, 31, 41, ..., nl) comprises a first calibration receiver configured to receive a first calibration signal over a second data transmission line ; and in that the second data interface (31, 41, ..., nl) comprises a second calibration transmitter configured to transmit the first calibration signal over the second data transmission line, and a second control circuit (32, 42, ..., n2) configured to generate the first calibration signal in response to receipt of the first trigger signal by the second trigger receiver; wherein the first control circuit is configured to determine an elapsed time between transmission of the first trigger signal by the first trigger transmitter and receipt of the first calibration signal by the first calibration receiver. a first ranging unit comprising: a first laser driver (23, 33, 43, ..., n3); a first control circuit (22, 32, 42, ..., n2) configured to generate a first trigger signal; and a first data interface (21, 31, 41, ..., n1) comprising a first trigger transmitter configured to transmit the first trigger signal over a first data transmission line; and a first laser driver (23, 33, 43, ..., n3); a first control circuit (22, 32, 42, ..., n2) configured to generate a first trigger signal; and a first data interface (21, 31, 41, ..., n1) comprising a first trigger transmitter configured to transmit the first trigger signal over a first data transmission line; and a second ranging unit comprising: a second laser driver (33, 43, ..., n3); a second data interface (31, 41, ..., n1) comprising a second trigger receiver configured to receive the first trigger signal over the first data transmission line ; characterized in that the first data interface (21, 31, 41, ..., nl) comprises a first calibration receiver configured to receive a first calibration signal over a second data transmission line ; and in that the second data interface (31, 41, ..., nl) comprises a second calibration transmitter configured to transmit the first calibration signal over the second data transmission line, and a second control circuit (32, 42, ..., n2) configured to generate the first calibration signal in response to receipt of the first trigger signal by the second trigger receiver; a second laser driver (33, 43, ..., n3); a second data interface (31, 41, ..., n1) comprising a second trigger receiver configured to receive the first trigger signal over the first data transmission line ; characterized in that the first data interface (21, 31, 41, ..., nl) comprises a first calibration receiver configured to receive a first calibration signal over a second data transmission line ; and in that the second data interface (31, 41, ..., nl) comprises a second calibration transmitter configured to transmit the first calibration signal over the second data transmission line, and a second control circuit (32, 42, ..., n2) configured to generate the first calibration signal in response to receipt of the first trigger signal by the second trigger receiver; wherein the first control circuit is configured to determine an elapsed time between transmission of the first trigger signal by the first trigger transmitter and receipt of the first calibration signal by the first calibration receiver. <EOS>