Accuracy of wind farm visualisations: The effect of focal length on perceived accuracy

Wind energy has been the fastest growing renewable energy technology for more than a decade. However, the visual impacts of wind farms are still one of the most controversial effects of wind energy development. Photomontage visualisations are frequently used in Visual Impact Assessments² (VIA) to give a sense of scale of the proposed development. Yet visualisations in VIAs are often perceived to underestimate the scale and magnitude of the visual impact of wind turbines. The aim of this multiphase mixed methods study is to explore the perceived accuracy of images that represent the visual impacts of both onshore and offshore wind farms. Field visits and data from a public survey are used to assess the accuracy of visualisations and to examine the effect of camera lens focal length on perception of scale of wind turbines. Results show that panoramic photomontages are perceived as the least accurate, while images taken at 75 mm focal length in full frame format are perceived as the most accurate form of representation of the scale and visual impact of wind turbines. These findings imply that the panoramic visualisation technique, which has been used for decades to predict the scale of wind turbines in VIAs, is ineffective in predicting accurately the visual impact of wind farms, and an alternative predictive technique is needed. For wind farm visualisations the use of 75 mm full frame image format is recommended in order to improve the accuracy, enable better informed decision making and avoid the loss of credibility of visualisations and VIAs.