The aim of the project was to establish the suitability of aerial imagery taken from Unmanned Aerial Vehicles (UAV) to investigate the spatial and temporal extent of bait digging at selected sites in Wales.

Sites were flown at low tides and ortho-rectified seamless mosaics produced. Shore survey and ground truthing was also undertaken, and control holes dug to investigate the persistence of bait digging evidence on different shores. The shores were revisited to assess whether the control holes were still visible, to give an indication of the persistence of damage. The ortho-rectified imagery was used to create bait digging intensity maps on a variety of shore types.

Further information from Crispin Flower.

NRW contracted Exegesis to establish a vegetation monitoring programme that would allow the development of the saltmarsh to be assessed and better understood. This involved:

• Collection of high-resolution aerial photography using out fixed-wing drone.
• The generation of an accurate height model.
• Capture of vegetation communities based on species dominance from the aerial photography and data collected in the field. The resolution of the aerial photography made sub-metre precision mapping possible.
• The selection of three transects across the main site.
• Detailed survey of a series of randomly located 2×2 metre quadrats along the transects, located using a high precision GPS.
• Photographs of transects, quadrats and features of interest.
• A full technical report detailing the methodology and results.

The report recommended repeat monitoring surveys following the same methodology and using the same quadrat locations, so that future vegetation change could be quantified and characterised.

Further information from Crispin Flower.

The survey was undertaken by our mini-plane less than 24 hours after the initial request was made. In order to attain the highest level of spatial accuracy, ground control points were taken with a high precision GPS unit. The images were orthorectified and mosaicked to create a single image using Pix4UAV advanced processing software.

We also used Pix4UAV to generate a digital surface model (DSM) to enable 3D analysis to be undertaken. This DSM was compared against lidar data, which provided a baseline height for the site before the addition of material. The lidar data was subtracted from the DSM to give the change in height, which was then analysed to determine the volume of additional material within discrete patches identified from the aerial photography. The volumetric analysis was undertaken using GRASS and verified with MapInfo Engage 3D.

The aerial images, DSM and outputs of the analysis were provided to the client, along with a report describing the methodology used and the results.

Further information from Crispin Flower.