## 4 Deployment Validation Strategies  
As already stated, the lidars were planned to operate stand-alone offshore for many months. This prompted a need for pre- and post-deployment validations. Thus the NORSEWInD deployment validation strategies included three major steps: Pre-deployment validation onshore, data collection and operational performance validation at sea, and post-deployment validation onshore. The pre- and post-deployment validations onshore took place at the DTU Wind Energy's Hovsore test site on the Danish North Sea coast next to a 116 m tall meteorological mast on flat terrain. The observations from the lidars were compared to the mast observations at the levels 60, 80, 100 and 116 m. The local set up arrangement is shown in Figure 4.  
Prior to the pre-deployment validation a standard for the data quality acceptance levels for the NORSEWInD lidar systems was defined. This is the so-called \"NORSEWInD standard\" and the details are given in Table 1.  
The pre-deployment validation included eight lidars. Figure 5 shows the comparison results between observed wind speeds from cup anemometer and lidar measurements at 100 m for one of the lidars. The observations are from the wind sector 200\({}^{\circ}\) to 300\({}^{\circ}\) at Hovsore (see the sector in Figure 4). The linear regression slope and R\({}^{2}\) at all observational heights for the eight lidars tested for y = mx are listed in Table 2. Only three instruments (1, 7 and 9) did not fully pass the criteria. The poorer values are highlighted in grey. The results of the verification for these systems may be seen to be only slightly out of range except for the measurement at 60 m by Lidar 1. Lidars 1 to 5 are WindCubes. Lidars 6 to 8 are ZephIRs. The pre-deployment validation showed excellent results for most of the lidars deployed. The slopes and correlation coefficients are slightly lower for the Zephirs than WindCubes except for Lidar 1. The reason may be due to comparison between point data from the mast to line scanning from pulsed lidars (WindCube) and volume scanning (Zephirs) from remote sensing data. Figure 4: Hovsøøre mast and lidar set up sketch. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Lidar**} & \multicolumn{2}{c}{**Slope at**} & \multicolumn{2}{c}{**R\({}^{2}\) at**} \\  & **116 m** & **100 m** & **80 m** & **60 m** \\ \hline
1 & 0.991 & 0.976 & 0.977 & 0.948 \\
2 & 0.988 & 0.992 & 0.991 & 0.993 \\
3 & 0.993 & 0.997 & 0.997 & 1.000 \\
4 & 0.996 & 0.999 & 0.998 & 0.998 \\
5 & 0.985 & 0.993 & 0.992 & 0.993 \\
6 & 0.983 & 0.986 & 0.986 & 0.990 \\
7 & 0.978 & 0.983 & 0.984 & 0.992 \\
8 & 0.976 & 0.980 & 0.977 & 0.989 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Pre-deployment validation results shown for eight lidars tested at Høvøøre: Linear correlation slope and R\({}^{2}\) for the wind speeds in the range from 4 to 16 m\(\cdot\)s\({}^{-1}\) at four heights. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Parameter**} & \multicolumn{1}{c}{**Criteria**} & \multicolumn{1}{c}{**Ranges**} \\  & \multicolumn{2}{c}{**(Height and Speed)**} \\ \hline \multirow{4}{*}{Absolute error} & \(<\)0.5 m\(\cdot\)s\({}^{-1}\) for 2 \(<u<\) 16 m\(\cdot\)s\({}^{-1}\) & \\  & Within 5\% above 16 m\(\cdot\)s\({}^{-1}\) & All valid data \\  & Not more than 10\% of data to exceed those values & \\ \multirow{4}{*}{Data availability} & Assessed case by case & \\  & Environmental conditions dependency & All valid data \\ \multirow{2}{*}{Linear regression} & Slope between 0.98 and 1.01 & Heights from 60 to 116 m \\  & \(<\)0.015 variation in slope between & \(u\)-ranges: (a) 4–16 m\(\cdot\)s\({}^{-1}\), \\  & \(u\)-ranges (b) and (c) & (b) 4–8 m\(\cdot\)s\({}^{-1}\), (c) 8–12 m\(\cdot\)s\({}^{-1}\) \\  & & Heights from 60 to 116m \\  & \(>\)0.98 & \(u\)-ranges: (a) 4–16 m\(\cdot\)s\({}^{-1}\), \\  & & (b) 4–8 m\(\cdot\)s\({}^{-1}\), (c) 8–12 m\(\cdot\)s\({}^{-1}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Data quality acceptance levels for NORSEWInD lidar systems. \(u\) stands for wind speed.