Practical Geometry is a set of very simple measuring techniques which predate arithmetic. These methods are meant for construction of real objects and environments, and are still used today by carpenters and masons.
My interest in Practical Geometry is how it may be adapted to draft and organize wall paintings. As a painter, it seems interesting to address architecture with the borrowed language of buildings. Making measurements reveals things about the place. The economy of means is attractive. Designs scale up easily from sketchbook to facade. And the results are self evident, they draw themselves and make plain their process.
These exercises demonstrate wall-size drafting that I find interesting with just strings, nails, and a spray paint bracket.
Ellipse From 2 Points
Three Vertex Ellipse
Combination of Semicircles
Shrinking Ellipses Perimeters / 2 Fixed Points
Crescent from 2 Points
Parallel Non-Straight Lines
Moire Pattern from 2 Sets of Concentric Arcs
Combination of Arcs from 3 Points
Combination of Concentric Semi-Circles
4 Tangent Half-Circles from 3 Points
3 Tangent Half-Ellipses
Combination of Tangent Half Ellipses and Semi-Circles from 2 Points
*For further reading, try these beautiful books: The Library of Practical Geometry http://practicalgeometry.ca/, By Hand & Eye https://lostartpress.com/collections/books, and How Round is your Circle http://press.princeton.edu/titles/8624.html.