Add example with ETOPO online dataset

[veenstrajelmer]

ETOPO 2022 30arcseconds is available via opendap (use surface, not bedlevel). There is also a 15 arcsecond dataset, but this is split up in multiple files.

import xarray as xr
import dfm_tools as dfmt

lon_min, lon_max, lat_min, lat_max = -75, -70.9, 39, 43
file_nc = r"https://www.ngdc.noaa.gov/thredds/dodsC/global/ETOPO2022/30s/30s_bed_elev_netcdf/ETOPO_2022_v1_30s_N90W180_bed.nc"

data_bathy = xr.open_dataset(file_nc)
data_bathy_sel = data_bathy.sel(lon=slice(lon_min-1, lon_max+1), lat=slice(lat_min-1, lat_max+1))

data_bathy_sel.z.plot(robust=True)
dfmt.plot_coastlines()

Gives:

The data is also available on p:\metocean-data\open\ETOPO\2022\15s_surface_elev_netcdf. To auto-concat all datasets, use ds = xr.open_mfdataset(nc_files, combine='by_coords')