Illegal option --
usage: /usr/bin/geographiclib-get-geoids [-p parentdir] [-f] [-d] [-h] geoid...

This program downloads and installs the datasets used by the
GeographicLib::Geoid class and the GeoidEval tool to compute geoid
heights.  These datasets are NGA earth gravity models evaluated on a
rectangular grid in latitude and longitude.  geoid is one of more of the
names from this table:

                                  size (MB)
  name         geoid    grid    tar.bz2  disk
  egm84-30     EGM84    30'      0.5      0.6
  egm84-15     EGM84    15'      1.5      2.1
  egm96-15     EGM96    15'      1.5      2.1
  egm96-5      EGM96     5'       11       19
  egm2008-5    EGM2008   5'       11       19
  egm2008-2_5  EGM2008   2.5'     35       75
  egm2008-1    EGM2008   1'      170      470

The size columns give the download and installed sizes of the datasets.
In addition you can specify

  all = all of the supported geoids
  minimal = emg96-5
  best = egm84-15 egm96-5 egm2008-1 (the highest resolution for each
         earth gravity model)
  good = same as best but substitute egm2008-2_5 for egm2008-1 to save
         on disk space

-p parentdir (default /usr/share/GeographicLib) specifies where the
datasets should be stored.  The "Default geoid path" listed when running

  GeoidEval -h

should be parentdir/geoids.  This script must be run by a user with
write access to this directory.

Normally only datasets which are not already in parentdir are
downloaded.  You can force the download and reinstallation with -f.
The -f flag also let you download new models (not yet in the set
defined by "all").

If -d is provided, the temporary directory which holds the downloads,
$TMPDIR/geoid-XXXXXXXX or /tmp/geoid-XXXXXXXX,
will be saved.  -h prints this help.

For more information on the geoid datasets, visit

  https://geographiclib.sourceforge.io/C++/doc/geoid.html