Map overlay & algebra
=====================

.. raw:: html

    <iframe src="https://docs.google.com/presentation/d/e/2PACX-1vQs2gnILtgqyGES5TQfuHhwKo1vkJ_e08az4K5qVjXLCDjocnz4QxsOtoxfOARyMK99WNI9KuwlztSz/embed?start=false&loop=false&delayms=3000" frameborder="0" width="700" height="422" allowfullscreen="true" mozallowfullscreen="true" webkitallowfullscreen="true"></iframe>