Recently, the number of optical systems that operate along near horizontal paths within a few meters of the ground has increased rapidly. Examples are LIDAR or optical sensors imbedded in a vehicle, long range surveillance or optical communication systems, a LIFI network, new weather monitoring stations, as well as directed energy systems for defense purposes. Near ground turbulence distortion for optical waves used in those systems cannot be well described by conventional turbulence and beam propagation theory. Phenomena such as anisotropy, micro mirage effects, a temporal negative relation between diurnal dips and altitude, and condensation induced measurement errors are frequently involved. As a result, there is a high risk of defective designs or even failures in those optical systems if the near ground turbulence effects are not well considered. To illustrate such risk, we make C_n² measurements by different approaches and cross compare them with associated working principles. By demonstrating the reasons for mismatched C_n² results, we point out a few guidelines regarding how to use the general anisotropy theorem and the risk of ignoring it. Our conclusions can be further supported by an advanced plenoptic sensor that provides continuous wavefront data.

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Chensheng Wu, Daniel A. Paulson, Miranda Van Iersel, Joseph Coffaro, Melissa Beason, Christopher Smith, Robert F. Crabbs, Ronald Phillips, Larry Andrews, and Christopher C. Davis, "Near ground surface turbulence measurements and validation: a comparison between different systems," Proc. SPIE 10770, Laser Communication and Propagation through the Atmosphere and Oceans VII, 107700K (Presented at SPIE Optical Engineering + Applications: August 21, 2018; Published: 18 September 2018); https://doi.org/10.1117/12.2322723.