13e89cce2ea749be010007cba3bb4f09 English P11684 dataset Gareth Myers-McCann APEM Limited Data Operations Team dot@apemltd.co.uk pointOfContact 2024-02-23 MEDIN Discovery metadata standard 2.3.8 urn:ogc:def:crs:EPSG::4326 2023-2024, APEM, POSEIDON, Celtic Sea Seabird and Marine Mammal Surveys 2024-01-19 creation P11684_S01 This report constitutes the first seasonal (October to December 2023) report outlining results from digital aerial surveys conducted in November 2023 within the South-West Celtic Sea under the POSEIDON project and commissioned by Natural England. Surveys were undertaken using APEM’s high-resolution camera system to capture digital still imagery of birds and marine megafauna within the Survey Area. The survey was successfully carried out across two non-consecutive days in November 2023, with one day between surveys. There were no safety issues. A total of 747 observations were recorded in November 2023, of which 584 were observations of birds and 163 observations were of marine megafauna. APEM will continue to monitor the site for these species and others during the remaining seasonal surveys. Gareth Myers-McCann APEM Limited Data Operations Team dot@apemltd.co.uk originator The Crown Estate +44 020 7851 5000 1 St James's Market enquiries@thecrownestate.co.uk custodian notPlanned Delimited Bird counts SeaDataNet P021 parameter discovery vocabulary 2009-11-16 revision Bird behaviour Cetacean abundance Cetacean behaviour Research Research and Development Activity Marine Environmental Data and Information Network Marine Environmental Data and Information Network otherRestrictions No restrictions to public access Data is freely available for research or commercial use providing that the originators are acknowledged in any publications produced. eng biota Charting Progress 2 Sea Areas 2009-06-18 creation Western Channel and Celtic Sea International Hydrographic Bureau, Limits of Oceans and Seas 1954-01-01 creation North Atlantic Ocean SeaDataNet vertical extent keywords 2010-01-01 revision troposphere -9.0000 -9.4500 48.5000 49.5000 -9.3600 -10.3700 48.1200 48.5600 -10.3700 -10.8300 47.4600 48.1800 2023-11-21 2023-11-23 https://www.marinedataexchange.co.uk/details/TCE-3993/summary A link to the web service or dataset. https://www.marinedataexchange.co.uk A link to the general host site. dataset MEDIN data guideline for photo-identification of cetaceans and surface swimming sharks 2011-02-02 publication Cetaceans and surface swimming sharks may be detected in offshore aerial surveys true MEDIN data guideline for ad hoc sightings 2012-12-19 publication No specification of direct applicability to digital aerial surveys of birds true The survey was conducted using APEM’s bespoke camera system, termed “Shearwater V”, customised by in-house specialists for surveying the offshore environment. The camera system is integrated with custom flight planning software that allows each survey flight line to be accurately mapped before the aircraft leaves the ground. Each image capture node is precisely defined, allowing the system to fire the camera exposures at exactly the right location. This ensures that each survey is flown with the same orientation and the camera is triggered at the same position within set tolerances. APEM’s flight planning software enables tolerances along survey lines to be set, meaning the camera system would automatically abort data capture should the aircraft drift away from the planned flight line. The process of automatically aborting data capture is called a ‘cutout’. Should this occur, the plane is required to revisit and resurvey the affected section of the survey line. APEM’s on-board camera technician continually monitored the imagery as it was collected to ensure data collected was fit for purpose. The camera technician would make the decision to cease data collection should conditions become unsuitable for surveying or data collection. Subsequently, the survey would then be resumed at the next earliest opportunity. All completed surveys therefore maintained conditions conducive to successful surveying. Favourable conditions for surveying were defined as: a cloud base (lowest altitude of the visible portion of the cloud) of at least 1,300 ft, according to a geoidal model, to ensure there is no cloud below the planned altitude of the aircraft, visibility of greater than 5 km, wind speed of less than 30 knots, and sea state of 4 (moderate) or less. Naturally, the cloud base may vary in altitude, but aircraft will always fly lower than the lowest cloud level. If cloud base is lower than the planned aircraft altitude the survey would not take place. Whilst the image footprint and GSD both increase with altitude, the focus of the camera lenses ensures no discernible differences within the range of altitudes potentially flown. Wind speed was recorded at the same altitude as the aircraft, whereas sea state was determined from the appearance of the sea surface recorded by the onboard aerial survey technician. The two measures therefore do not necessarily correlate. For safety reasons, no surveying can take place in icing conditions. Data capture comprised digital still images of an average 1.5 cm GSD. Images at each camera are processed at each node, resulting in slight variation in GSD across the swath width. GSD is smaller than 1.5 cm GSD at the nadir and increases with distance from the nadir, resulting in an average GSD of 1.5 cm. Image resolution is therefore clearest at the nadir, although the variation is small. Images were collected in a continuous transect-based design along a single line covered by three overlapping cameras, using a Global Positioning System (GPS) linked, bespoke flight management system to ensure the tracks were flown with a high degree of accuracy. The aircraft’s internal GPS and Inertial Motion Unit (IMU) systems record to an accuracy of +/- 3 to 5 m as standard. The camera system captured abutting imagery along 11 survey flight lines spaced approximately 2 km apart within the Survey Area. The total Survey Area was 18,011 km2. The aircraft collected the data at an altitude of approximately 1,450 ft (440 m) according to the ellipsoid model as recorded by GPS, equivalent to 1,300 ft (395 m) above geoidal mean sea level, and at a speed of approximately 120 knots. Images were collected continuously along the survey flight lines with slight overlap between image nodes. To avoid double-counting due to image overlap, all image footprints are merged into a single file, for which total area is calculated. For analysis purposes each transect should be treated as a single sample, therefore for the current survey design, n=11. A total of 6,396 nodes were initially captured. Of these, 6,297 were used for analysis. The difference reflects nodes removed during clipping to the boundary area. Total coverage was calculated to be 3.30% captured and 3.30% analysed, generated from 6,297 image nodes. A total of six nodes were not captured on line 1. The target of 3% coverage was achieved, including a redundancy of an additional 0.30%, which reflects 10% contingency with respect to the target coverage. Effort data is calculated as the area (km2) per image footprint using trigonometric methods and the pinhole camera model (the mathematical relationship between the coordinates of a point in three-dimensional space, and its projection onto the image plane of an ideal pinhole camera). Effort is dependent on altitude, camera angle and aircraft position (pitch, roll and yaw), accounting for variation both between image nodes and individual cameras at each node. Summing analysed footprints and comparing against the entire survey area gives the percentage analysed. Effort values provided in the GPS log reflect the total footprint of each image and do not account for overlap. Therefore, summing these values for a survey would result in an overestimate of effort. The true effort for a given survey is calculated geospatially by creating polygons for each image and removing the overlapping areas. Imagery was captured in raw format and post-processed to ensure optimal quality for the subsequent stage of image analysis, to extract information on marine fauna or other notable occurrences. When a survey was completed, data were checked to ensure the number of lines and the number of images collected was correct, and that the quality of the imagery was acceptable. Once image analysis was completed, further quality assurance (QA) processes took place. Survey conditions are summarised in Table 3. Weather conditions are defined in Table 4. Weather conditions during the survey were conducive to collecting and analysing imagery for the purposes of providing data on the identification, distribution, and abundance of bird species and marine fauna within the Survey Area. Whilst relatively strong winds of up to 28 knots were recorded when surveying lines 1 and 2, they did not affect survey success or cause any health and safety issues. On 21st November, two planes were used to survey lines 1 to 5, and 8 to 11. The initial attempt to survey line 10 was unsuccessful due to camera flushing – a minor and easily-resolved hardware issue in which the camera’s memory fills faster than images are saved – resulting in missed nodes. Once the issue was rectified, the line was immediately re-surveyed. One plane attempted to survey lines 6 and 7 on 22nd November. However, low cloud prevented image capture. The lines were therefore re-surveyed on 23rd November. Measures were taken to minimise glint and glare, such as avoiding surveying when the sun angle had the greatest potential to impact image quality. Furthermore, data collected provided coverage of 3.30%, thus exceeding the 3% coverage required, enabling sufficient coverage to be collected should images be affected by glint or glare.