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Remote Sens. 2018, 10(9), 1465; https://doi.org/10.3390/rs10091465

Reducing the Uncertainty of Lidar Measurements in Complex Terrain Using a Linear Model Approach

1,†,‡,* , 2,‡
and
1,‡
1
Stuttgarter Lehrstuhl für Windenergie, Universität Stuttgart, Allmandring 5b, 70569 Stuttgart, Germany
2
WindFors—Universität Stuttgart, Allmandring 5b, 70569 Stuttgart, Germany
Current address: Allmandring 5b, 70569 Stuttgart, Germany.
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Received: 2 July 2018 / Revised: 4 September 2018 / Accepted: 10 September 2018 / Published: 13 September 2018
(This article belongs to the Special Issue Remote Sensing of Atmospheric Conditions for Wind Energy Applications)
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Abstract

In complex terrain, ground-based lidar wind speed measurements sometimes show noticeable differences compared to measurements made with in-situ sensors mounted on meteorological masts. These differences are mostly caused by the inhomogeneities of the flow field and the applied reconstruction methods. This study investigates three different methods to optimize the reconstruction algorithm in order to improve the agreement between lidar measurements and data from sensors on meteorological masts. The methods include a typical velocity azimuth display (VAD) method, a leave-one-out cross-validation method, and a linear model which takes into account the gradients of the wind velocity components. In addition, further aspects such as the influence of the half opening angle of the scanning cone and the scan duration are considered. The measurements were carried out with two different lidar systems, that measured simultaneously. The reference was a 100 m high meteorological mast. The measurements took place in complex terrain characterized by a 150 m high escarpment. The results from the individual methods are quantitatively compared with the measurements of the cup anemometer mounted on the meteorological mast by means of the three parameters of a linear regression (slope, offset, R 2 ) and the width of the 5th–95th quantile. The results show that expanding the half angle of the scanning cone from 20 to 55 reduces the offset by a factor of 14.9, but reducing the scan duration does not have an observable benefit. The linear method has the lowest uncertainty and the best agreement with the reference data (i.e., lowest offset and scatter) of all of the methods that were investigated. View Full-Text
Keywords: complex terrain; complex flow; lidar; VAD; remote sensing; wind energy complex terrain; complex flow; lidar; VAD; remote sensing; wind energy
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Hofsäß, M.; Clifton, A.; Cheng, P.W. Reducing the Uncertainty of Lidar Measurements in Complex Terrain Using a Linear Model Approach. Remote Sens. 2018, 10, 1465.

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