Using femtosecond laser pulses for electronic distance meter calibration

Electronic distance meters (EDMs) are widely used in different applications, such as surveying and civil engineering. In order to calibrate an EDM, different techniques can be used, including displacement interferometers and reference baselines. In this paper, an indoor baseline is designed and then accurately measured using femtosecond laser pulses from an optical frequency comb to be used for EDM calibration. The baseline consists of 13 fixed bases that cover 58 m distance. In order to accurately measure the distances between the bases, autocorrelation between femtosecond laser pulses is employed. The measurement shows a maximum precision of 14 µm over the 13 bases. Although this deviation is dominated mainly by the placement of the target mirror, the system capability is much more sufficient to safely calibrate the best available commercial EDM. The stability of the baseline is also investigated by measuring the interbase distances over long periods of time.