Sitting here reading the Nav section and I found something that I may as well share...
[quote author=FTGU, Opening Paragraph, Nav Section, p. 175]
The earth on which we live is a ball or sphere, technically an oblate spheroid. Not knowing any better, the human race has for centuries lived on the outside of the sphere, enduring heat and cold, clouds and rain, snow and sleet, fog, mist and mortal uncertainty. In due course, cities of the future may be located underground in a world of perfectly regulated conditions of heat, light, and fresh air. Meanwhile we are here today and gone tomorrow and must make the best of our cabbage-patch world, such as it is.
[/quote]
All from an aviation bible...