Accuracy of a Scanning Pulsed Coherent Wind Lidar Determined by Comparing With a Bistatic CW Lidar Traceable to SI Units

The Physikalisch-Technische Bundesanstalt (PTB) has built a bistatic coherent cw Doppler wind lidar with three receivers that has a probing volume small enough to fit into a wind tunnel and thus can be traced to a velocity standard. This contribution reports on concerted measurements of the mutually aligned PTB device and a SKIRON3D pulsed long-range wind lidar aiming to characterize the pulsed system's accuracy and minimize its bias with respect to the absolute reference (quasi calibration). Due to spatial averaging, it seems a bit unfair to ignore the dynamic and inhomogeneous nature of the target measurand in the statistical part of the accuracy (precision), but a reportable value should still be a constant. This dilemma is discussed in light of insights that would have been difficult to obtain in the absence of an absolute velocity reference. The mutual statistics of instantaneous values are analyzed and an upper limit for the accuracy of the pulsed system is proposed based on the findings.