Beach monitoring is a special type of survey used to collect data from an ever changing environment but put in a format which allows the different monitoring surveys to be compared scientifically. In the past, the surveys were instructed and carried out in a small scale, by local authorities and land owners without connection or thought regarding the wider environment. For the past years, local lead authorities are running 5 year frameworks, financed by DEFRA, to monitor most beaches around England.
AG Surveys was awarded 3 out of 4 areas in the SouthWest, stretching from St Austell to the M4 Severn Crossing near Bristol. A total of 80 beaches of varying sizes are surveyed up to 3 times a year, which usually involves profile line surveys. The profile lines are spaced every 50m along the beach and run from the back of the beach to Mean Low Water Springs (MLWS). Additionally, all beaches have a full baseline survey, where on top of the profiles the whole beach is measured with alongshore lines. Traditionally these baseline surveys were carried out with GNSS and in some areas static laser scanners have been used.
The company used it’s extensive knowledge gained from over 10 years of working in the coastal environment and purchased a Trimble UX5HP fixed wing drone to take survey grade photography of over 20 beaches least suited to manual GNSS data collection. All survey areas were pre-marked and the ground markers surveyed by GNSS similar to our normal GNSS work. Furthermore, check areas and check profile line were surveyed at the time to confirm the achieved accuracies of the drone data. In order to prove the viability of drone data, the client requested a change to the usual specification. All photography was analysed using specialised software before processed through Trimbe Business Centre (TBC) and INPHOs UAS Master programs. The 3D point cloud was then filtered and manually edited and checked before the final output created the usual data sets (bespoke client format text files) as well as the additional deliverables 3cm Orthophoto and 5cm grid pointcloud with coloured pixels. All our checks confirmed a height accuracy of better than 3cm compared to GNSS data.
So far we have flown over 100 missions and used over 50000 photographs to create bespoke, client led datasets, with accuracies as low as 20mm.