Hi!
The coastline mat file is created when you call make_grid. It calls the make_coast function where the file is created. The coastline data is in the DATASETS_CROCOTOOLS/m_map1.4f/private/ folder.
In the crocotools_param.m set the last letter of the file name prefix in coastfileplot variable according to the comment above it to set which coastline file will be used:
% GSHSS user defined coastline (see m_map)
% XXX_f.mat Full resolution data
% XXX_h.mat High resolution data
% XXX_i.mat Intermediate resolution data
% XXX_l.mat Low resolution data
% XXX_c.mat Crude resolution data
%
coastfileplot = 'coastline_l.mat';
coastfilemask = 'coastline_l_mask.mat';
Here it uses l - Low resolution data. If you change the name to coastline_h.mat' it will use high resolution data.
If you just want a higher resolution coastline mat file, you can just call make_coast directly. E.g.:
make_coast('CROCO_FILES/croco_grd.nc','coastline_h.mat')
Cheers!
Martin