A sub-millimetre two-wavelength EDM that compensates the air refractive index: uncertainty and measurements up to 5 km

This research project focuses on the development and evaluation of a two-wavelength electro-optical distance meter (EDM) designed for high-precision geodetic and structural deformation monitoring over long ranges. Operating at simultaneous wavelengths of 780 nm and 1560 nm, the system utilizes optical dispersion properties to achieve real-time compensation for the atmospheric refractive index along the measurement path. A key aspect of the research involves modeling the comprehensive uncertainty budget, which incorporates both telemetric and mechanical error contributions. A primary limitation addressed in the system architecture is optical crosstalk, primarily originating from optical splitters functioning as circulators, which degrades the signal-to-crosstalk ratio (SCR) over extended distances. Under optimal conditions where the SCR

exceeds 60 dB, the instrumental uncertainty in the air-index compensated distance is evaluated at approximately 320 µm (k = 1). The methodology provides a structured framework for analyzing long-range telemetry, supported by experimental field measurements conducted over distances of 2.6 km and 5.4 km. Project development support for this topic includes guidance on modeling optical dispersion, simulating crosstalk mitigation strategies, and structuring the uncertainty analysis for high-precision metrology applications.

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