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A method to measure long-range distances (>100 m) using a continuous-wave laser is presented. A continuous-wave laser beam at a wavelength in resonance with the water vapour absorption lines of water vapours at 1.52 μm is propagated to an object at a distance of 750 m, and the back-reflected signal is recorded. The atmospheric parameters (vapour pressure, temperature, atmospheric pressure) were recorded simultaneously with the laser back-reflection measurements. The water vapour concentration in the atmosphere is calculated from the atmospheric parameters. The distance from the laser sensor to the object is calculated using the differential absorption lidar (DIAL) method and the water vapour concentration. A 22 h experiment was performed to validate the methodology effectiveness during diurnal weather variation. Two water vapour absorption lines were used to calculate the distance to the object. The calculated distances were found to be 730 m ± 20 and 720 m ± 30 (2.7% and 4.0% deviation, respectively, compared to the actual distance). [ABSTRACT FROM AUTHOR]

A ground-based, integrated path, differential absorption (IPDA) light detection device capable of measuring multiple greenhouse gas (GHG) species in the atmosphere is presented. The device was developed to monitor greenhouse gas concentrations in small-scale areas with high emission activities. It is equipped with two low optical power tunable diode lasers in the near-infrared spectral range for the atmospheric detection of carbon dioxide, methane, and water vapors (CO2, CH4 and H2O). The device was tested with measurements of background concentrations of CO2 and CH4 in the atmosphere (Crete, Greece). Accuracies in the measurement retrievals of CO2 and CH4 were estimated at 5 ppm (1.2%) and 50 ppb (2.6%), respectively. A method that exploits the intensity of the recorded H2O absorption line in combination with weather measurements (water vapor pressure, temperature, and atmospheric pressure) to calculate the GHG concentrations is proposed. The method eliminates the requirement for measuring the range of the laser beam propagation. Accuracy in the measurement of CH4 using the H2O absorption line is estimated at 90 ppb (4.8%). The values calculated by the proposed method are in agreement with those obtained from the differential absorption LiDAR equation (DIAL). [ABSTRACT FROM AUTHOR]