Undertaking any wildlife survey is redundant unless you can then sufficiently identify what is found. Digital aerial surveys are extremely useful tools in the offshore renewables industry, providing accurate information that can subsequently be used when assessing the potential environmental impact of constructing offshore infrastructure.

In comparison to the historically relied upon boat-based surveys or the more modern aerial surveys completed by human observers, the digital aerial method provides more reliable and robust data. The APEM Group continually incorporates technological advances to aid in improving species identification rates and aid offshore wind development.

Dr Steph McGovern is Divisional Director for Wildlife Surveys and was part of the pioneering team developing digital aerial surveys for wildlife since 2011. Since then she has been evolving APEM Group’s digital aerial survey design which now is industry-leading across the world. Steph presented ‘The use of LiDAR technology to measure site-specific offshore avian flight heights’ in September 2022 at the State of the Science Workshop on Wildlife and Offshore Wind Energy. 

Collison is one of the main mortality factors for avian species caused by operational offshore windfarm (OWF) developments. Typically, this is assessed using collision risk models which require avian flight heights as an input. Historically, flight heights have been estimated from available literature, boat-based surveys, or size-based calculations from aerial digital still imagery. These methods are subject to variable error and subsequent bias within the calculations, which leads to uncertainty around the results, which can lead to overly precautious estimates of collision. This paper describes a new measurement methodology for collecting site-specific avian flight heights in the offshore environment.

LiDAR (Light Detection and Ranging) technology is an accurate survey method that measures distances using laser light. Traditionally this technology has been applied as a topographic mapping tool. APEM has developed an approach which utilizes a custom-built system that captures both high-resolution digital still imagery and LiDAR positional data of avian species concurrently. Birds in flight are identified to species level from the imagery and the flight height is measured by “hits” from the LiDAR system. When the two data sets are combined, this methodology provides accurate avian flight heights which are site and species-specific. Proof of concept studies have produced confident matches between imagery and LiDAR data, with >95% of flying birds having flight height measurements within one meter accuracy. Preliminary data show that matching high-resolution images with the LiDAR, show a high rate of success even with birds flying close to the sea surface, with our results accurately depicting birds captured at all heights. Furthermore, species size does not appear to affect the results, with even small birds (<40 centimeters) achieving a mean LiDAR hit rate greater than one.

Image of Gannets being highlighted by LiDAR

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This technology will help to fill important knowledge gaps around site-specific avian flight heights. The simultaneous use of LiDAR and digital still imagery provides flight height measurements that can more accurately and precisely inform collision risk models than traditional methods, reducing the levels of precaution required around OWF developments. Although in its early stages, results from trials of this technology demonstrate that it is likely to become the most appropriate tool from which to generate site-specific avian flight height data.

In November 2022 Natural England (the UK’s nature and conservation body), endorsed its use in their best practice advice.

The APEM Group have been supporting clients in the offshore wind industry across the world for over 15 years, trusting us to demonstrate best practice and ensure that the data delivered meets the necessary legislation for the location surveyed.

Our early adoption of digital aerial survey methods has ensured that we are a global leader in this field of expertise, however, we are constantly looking at new ways of working and methodologies to ensure we are delivering the most reliable and robust data for our clients.

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