The 25 cm Digital Surface Model (DSM) 2022015FA_Truro_DSM_25cm.tif and 1 m bathymetry grid 2022015FA_Truro_bathymetry_1m.tif (available from the larger work citation) were merged and interpolated over a 1 m grid in MATLAB v. 2020b with the following steps.
1. The data (x,y,z) from the DSM and Bathy grids were combined with the interpolation method regularizedata3d (bicubic interpolation) using a smoothness coefficient of 0.001 (used for data with low noise where the input points nearly coincide with the output surface) by Jamal (2020).
2. The combined grid was then masked using 'roipoly' which returns the mask as a binary image, setting pixels inside the region of interest polygon to 1 and pixels outside the region of interest (ROI) to 0. The boundary was determined by specifying the polygon vertices as the regularizedata3D outputs (x,y,z) from the previous step and prevented extrapolation beyond the tracklines of the bathymetry and DSM extent.
3. The final merged GeoTIFF was created using the GRIDobj tool in the TopoToolbox (Schwanghart and Scherler, 2014), which used the interpolated grid from Step 1 and the mask from step 2 to create the final output. The GeoTIFF was exported in NAD83(2011)/UTM Zone 19N in NAVD88 meters, using Geoid 12B. Note that using NAVD88 as a height means that the depths are not true-depths but the elevation of the seafloor above or below the geoid.
Schwanghart, W., Scherler, D. (2014): TopoToolbox 2 – MATLAB-based software for topographic analysis and modeling in Earth surface sciences. Earth Surface Dynamics, 2, 1-7. [DOI: 10.5194/esurf-2-1-2014]
Jamal (2020). RegularizeData3D (
https://www.mathworks.com/matlabcentral/fileexchange/46223-regularizedata3d), MATLAB Central File Exchange. Retrieved September 23, 2020.
