CEFAS24-146 Contract for Light Detection & Ranging (LiDAR) surveys at Sizewell.

Description

To support the delivery of the BEEMS Programme, Cefas have the requirement to work with a supplier to assess error margins around estimates of the ground elevation under dune and coastal vegetation at Sizewell-Minsmere. Accurate, or slightly conservative, estimates of the beach and dune surface under vegetation are required to ensure that beach volumes (specifically Soft Coastal Defence Feature (SCDF) volumes) are not over-estimated which could otherwise result in delayed SCDF maintenance triggers and maintenance, and increased risks of SCDF buffer & Hard Coastal Defence Feature (HCDF) exposure. The supplier is required to test the next generation of Light Detection and Ranging (LiDAR) sensors, which have more power and improved laser to penetrate further into the vegetation, against elevations from detailed ground truthing Global Navigation Satellite System (GNSS) and Red Green Blue (RGB) optical imagery. Surveys are required to be undertaken when coastal vegetation is at its minima, average and maxima (c. January, March/April and June). The proposed work will include three LiDAR surveys, each with accompanying ground truth surveys, collected with a GNSS receiver rover (short occupation only, no tripod required). Accuracy requirements for ground truthing measurements are to be within Root Mean Square Error (RMSE) ±3cm horizontal and ±4cm vertical, equivalent to a detailed survey performed under relative kinematic methodology as per RICS 'Use of GNSS in land surveying and mapping 3rd edition' standards. Please see supporting documents contained within the bidder pack for details of the survey area, and minimum expected ground truthing points. Each summary report will require the supplier to: • Extract the LiDAR Digital Terrain Model (DTM) elevation (if more than one model has been used then extract for each model), the LiDAR Digital Surface Model (DSM) point cloud mean and minimum elevations, and the RGB optical DSM elevation, at each ground truth location. o To be performed separately for calibration and validation data, and then performed all together. • Generate difference statistics for the ground truth validation points in the LiDAR DTM and compare with the LiDAR calibration points • Generate difference statistics and graphics for all methods against the ground truth values. • Draw conclusions about different methods and how well they estimate the true ground surface both in general and specifically for each broad vegetation type (low grass, dune vegetation, reeds, gorse, shrubs/trees). Express this in elevation and beach volume terms (Cefas will provide the method for the latter) • Present the results for Cefas in advance of a short report on all of the above.