Does atmospheric turbulence affect long-range terrestrial laser scanner observations? A case study in alpine region

Abstract

Optical or microwave measurements from numerous geodetic devices are affected by their path through the atmosphere. Deterministic changes in the atmospheric refractivity index can be modelled and, to some extent, corrected. On the other hand, random fluctuations coming from atmospheric turbulence correlates the observations thus reducing the effective number of available observations. They have to be accounted for to get a realistic description of the measurement error but also to increase the reliability of early warning system within the context of risk management with light detection and ranging (lidar) sensors. We have developed a novel method to investigate the impact of turbulence on long-range laser scanner observations by searching prisms within repetitive scans at different times of the day, during consecutive days in a mountainous region in Austria. The empirical analysis of the power spectral density of the measurements combined with information from meteorological sensors (pressure, temperature, wind velocity) help gaining a better understanding of how and when turbulence affects the range measurements. Our method gives an averaged description of turbulence across the atmospheric layers travelled by the laser light, and paves the way for the development of an improved stochastic model for such observations without using additional equipment such as scintillometers.