Automated Assessment of Lidar Uncertainty in Complex Terrain

Introduction

For WRA & site suitability analysis in complex sites, it’s crucial to have reduced measurement uncertainty from a vertical profiler as well as the ability to move the Lidar from one location to the other with the same uncertainty. Prior knowledge of this uncertainty and appropriate regulations on optimal locations for Lidar profilers in complex sites are important for developers and consultants to plan a future field campaign.

Approach

In this paper, the uncertainty arising from moving a Lidar from one location to the other in complex terrain is studied. Cartography of uncertainty for a given complex site is created, based on the terrain slope and surrounding roughness. This is then used to identify locations where the uncertainty at a given site is expected to be lower and/or additional data correction like FCR or more advanced CFD is required.

Main body of abstract

The uncertainty from a vertical profiler compared to a point measurement in complex terrain arises from the flow in-homogeneity over the sensing volume. Several advanced methods are available in the literature to use the Lidar measurements and provide a measurement similar to the cup anemometer without using the homogeneity assumption. Such techniques may be the FCR add-on (Flow Complexity Recognition) or CFD post-corrections. For WRA & site suitability analysis in complex sites, prior knowledge of measurement uncertainty of vertical profiler as well as the ability to move the Lidar from one location to the other is crucial for planning a successful field campaign. Cartography maps of estimated measurement uncertainties would assist developers in optimal measurement setup in order to obtain reduced project uncertainty in complex terrain sites, as well as anticipate if they would require the use of FCR or CFD corrections. The Lidar uncertainty maps are calculated for Windcube Lidars with and without FCR. The maps may be given at different scales, from large areas such as Europe to a wind farm scale. Finally, by using these maps, the paper will assess the overall gain by moving the Lidar from one location to the other in complex sites compared to a traditional measurement.

Conclusion

The results from several field campaigns will provide a cartographic view of Lidar measurement uncertainties and help define optimal siting in complex sites in order to design successful field measurement campaigns.


Learning objectives
1. Regulations of Windcube with and without FCR in complex sites

2. Estimated measurement uncertainty in complex terrain for WRA & Site Suitability analysis using Lidars

3. Cartography of uncertainties in Europe and at a selection of operating sites.