The 25 cm Digital Surface Model (DSM) 2020015FA_Truro_DSM_25cm.tif and the 1 m bathymetry grid 2020015FA_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 are combined with the interpolation method regularizedata3d (bicubic interpolation) with 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. Combined grid is 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 ROI to 0. The boundary is determined by specifiying the polygon verticies as the regularizedata3D outputs (x,y,z) from the previous step and prevents extrapolation beyong the tracklines of the Bathy and DSM extent.
3. The final merged GeoTIFF is created using the GRIDobj tool in the TopoToolbox (Schwanghart and Scherler, 2014) which uses the interpolated grid from Step 1 and the mask from step 2 to create the final output. The GeoTIFF is output in NAD83(2011)/UTM Zone 19N in the vertical datum NAVD88 in meters.
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.