.. blogpost::
    :title: Installation of proj
    :keywords: cartopy, proj
    :date: 2019-09-21
    :categories: installation

    This is required for :epkg:`cartopy`,
    `PROJ <https://proj.org/install.html>`_ needs to
    be installed otherwise the following error appears:

    ::

        setup.py:171: UserWarning: Unable to determine GEOS version. Ensure you have 3.3.3 or later installed, or installation may fail.
        '.'.join(str(v) for v in GEOS_MIN_VERSION), ))
        Proj 4.9.0 must be installed