In this, the first of two articles, BSG Ecology Partner Steve Betts outlines some of the opportunities for using unmanned aerial vehicles (UAVs or drones) in ecology surveys, and outlines the regulatory requirements that need to be considered ahead of commercial use.
Technological Advances:
Drone technology has advanced considerably in recent years and the sophisticated equipment that is now available presents some interesting opportunities. BSG Ecology is currently working with clients to develop applications for drones that will assist with the ecological assessment of sites.
High quality (high resolution) aerial imagery has not, until recently, been readily available to ecologists, due to the requirement to use expensive specialist equipment and the high cost of commissioning aerial surveys to capture such images. However, technological advances mean that digital cameras have reduced in size without compromising quality, and these improvements have been incorporated into the latest generation of drones. Whilst images available on the internet via sources such as Google Earth have some use, much higher resolution imagery can now be obtained relatively easily using drones.
High quality aerial images potentially offer a number of benefits to ecologists, particularly when assessing the ecological interest of sites, but in order to get the most from this technology it is important to appreciate its limitations as well as the opportunities that it presents. Most importantly there are restrictions on the use of drones that users need to be aware of, which means that you cannot simply buy a drone and use it for commercial purposes. Consideration also needs to be given to the resolution of the camera and hence the distance that the drone needs to be from the target to achieve the desired results. If the objective is to use the drone to monitor animals, close proximity of the drone also potentially raises issues relating to their disturbance.
Civil Aviation Authority Requirements:
The Civil Aviation Authority (CAA), which is the UK’s aviation regulator, has introduced regulations that require operators of small unmanned aircraft used for aerial work purposes and those equipped for data acquisition and/or surveillance, to obtain permission from the CAA before commencing a flight in certain situations. Permission needs to be obtained from the CAA if you plan to:
- fly the aircraft on a commercial basis (i.e. conducting ‘aerial work’) or
- fly a camera/surveillance fitted aircraft within congested areas or close to people or properties (vehicles, vessels or structures) that are not under your control.
In order to grant a permission, the CAA requires proof of the pilot’s overall airmanship skills and awareness, as well as their ability to operate the aircraft safely. This is achieved by means of an independent assessment, which is carried out by a small number of CAA-recognised training providers. The assessment comprises a ground theory course and examination, preparation of an operations manual and a practical airworthiness assessment that typically takes a number of weeks to complete.
Regulation:
The CAA has successfully prosecuted at least one person for the unauthorised use of a drone and further prosecutions are likely to follow in light of increasing concerns about impacts on manned aircraft. Irresponsible use of drones may ultimately result in further regulation of their use, which would be an undesirable outcome given the potential ecological applications that this technology can be used for. It is therefore important that ecologists only use drones once they have undergone the necessary training and in accordance with CAA guidance.
Application:
Steve Betts, Partner, has successfully passed his pilot training and is now using a drone to investigate its application in ecology. Initial work focussed on the use of the drone to help with the assessment of a former hospital building at St Mary’s Hospital, Stannington, near Morpeth, where access was limited as a result of the poor condition of the building. The results were very encouraging as the drone was used to investigate the roof, which otherwise would have required expensive scaffolding or a hydraulic lift to achieve the same result.
Steve has also been looking at the use of drones for habitat mapping and assessment work. They provide an efficient option for collecting high quality still and video images at sites, particularly those where physical access or terrain is dangerous or challenging, or areas that need to be surveyed are extensive. Large areas of land can be covered relatively quickly using a UAV, although the survey time will depend on the level of detail that is required and the type of drone used.
Operational Limitations
A Civil Aviation Authority (CAA) ‘Permit to Work’ typically allows drones to be operated under Visual Line Of Site (VLOS) rules, which means that they can be flown to a maximum height of 400 feet and a maximum horizontal distance of 500m from the operator. Consequently it should theoretically be possible to survey an area of 1km2 from a single launch site. If the survey area is larger than this, multiple launch sites / landing locations are likely to be required.
In addition to the requirement to obtain a Permit to Work from the CAA, it will also be necessary to obtain landowner permission for all areas that are to be overflown. Whilst the legal situation regarding flying over third party land is not particularly clear, it is advisable to seek permission to avoid complaints.
Habitat Assessment:
Aerial images provide a useful means of assessing habitat types using broad-scale mapping techniques. At its most basic level it is possible to characterise many habitats according to Phase 1 Habitat Survey classes, and in certain situations it may be possible to identify the boundaries of homogenous vegetation stands. To increase the robustness of the data it may be desirable to undertake a ground-truthing exercise, but for some habitats, such as certain grasslands and scrub, it is possible that robust characterisation can be achieved using aerial data alone.
Whilst drones provide a means of collecting data efficiently over an extensive area, they are also likely to be useful when surveying sites where access on foot is problematic, e.g. bogs, watercourses, cliffs, intertidal habitats. However, it should always be borne in mind that these habitats may potentially support populations of sensitive fauna, such as birds, and consequently disturbance may be an issue.
Software is available that will allow overlapping aerial photographs to be joined together to create an ortho-rectified[1] photo mosaic. The processing power of some software packages is very sophisticated, allowing three dimensional images to be created using information embedded in aerial images collected using drones. For example, a series of overlapping images covering a quarry site can be processed to create a three-dimensional image that shows the features of the void. The three-dimensional image can be used for accurate volumetric measurements, and can help with visualising a target whether it is the landform, a structure or a building.
Image Resolution:
The resolution of the digital camera is potentially a significant limitation to the application of the equipment. For example, a 12 megapixel camera[2] has a sensor with 4000 x 3000 pixel coverage. Image resolution will reduce with increasing distance from the subject, and ultimately this will dictate the maximum range at which the UAV can be used for a particular subject.
The following example illustrates this point. At an altitude of 20m a single pixel covers an area of approximately 30mm2: by comparison, at 40m elevation a pixel covers an area of approximately 125mm2 which means that there is significantly lower image resolution with increasing distance from the subject.
It therefore follows that resolution of small targets (e.g. leaves) may require that the UAV is close to the target. Whilst this will improve resolution, the trade-off is that the field of view (area covered) will be reduced. Consequently more still images are required to cover a given area of land, particularly if the objective is to generate ortho-rectified photo mosaics. The wide angle lenses used on some drones will result in some image distortion and so a high degree of image overlap is required to generate a good quality photo mosaic.
Application:
Steve has used a drone to assess habitats at various sites in Northumberland. In this example the drone has been used to photograph the Carey Burn, which is a small upland stream just outside Wooler.
Photograph 1 is taken at an altitude of about 50m and shows the physical context of the watercourse where the gently meandering channel is clearly visible. Riparian (bankside) habitats are identifiable and a split in the channel is obvious at the bottom of the image.
Photograph 2 shows a close up of the channel of the same watercourse taken at a height of about 5m. The bank vegetation, including grasses, rushes, ferns and shrubs, can be seen and the flow type is easily discernible. Using the drone it was possible to collect detailed photographic information over a 200m section of watercourse in a short period of time.
Notes:
[1] Ortho-rectification is the process of improving the horizontal accuracy of imagery.
[2] A 12 megapixel camera is mounted as standard on the DJI Phantom and Inspire drones.
First posted on 27 June and 6 July 2016 by Rowena Scott-Campbell in Company News, News and Views on BSG’s website HERE. To discuss the use of drones technology and the emerging BSG guidance or for advice on how drones can help with your project please contact Steven Betts, Partner – 0191 3038964
All images are ©BSG
Author’s Details: Steve Betts has worked in fisheries, ecology and nature conservation since 1992 and joined BSG Ecology in 2004. Prior to joining BSG Ecology, Steve worked for the Environment Agency and a multi-disciplinary consultancy. Steve has experience in a number of specialist areas including riverine and stillwater ecology, water quality, fisheries, habitat assessment and restoration and marine inter-tidal ecology.
